phentermine/topiramate (Rx)

Weight Management

Indicated as an adjunct to a reduced-calorie diet and increased physical activity for chronic weight management in adults with initial BMI ≥30 kg/m² (obese), or BMI ≥27 kg/m² (overweight) in presence of at least 1 weight related comorbidity (eg, hypertension, type 2 diabetes mellitus, dyslipidemia)

Initial: 3.75 mg/23 mg PO qDay for 14 days, THEN

Day 15: Increase to 7.5 mg/46 mg PO qDay for 12 weeks, then evaluate weight loss

After 12 weeks at 7.5 mg/46 mg: Evaluate weight loss; if adult has not lost at least 3% of baseline body weight, increase to 11.25 mg/69 mg qDay for 14 days; followed by an increase to 15 mg/92 mg qDay

After 12 weeks at 15 mg/92 mg: Evaluate weight loss for adults; if adult has not lost at least 5% of baseline body weight, discontinue phentermine/topiramate, as it is unlikely that the patient will achieve and sustain clinically meaningful weight loss with continued treatment

Note: 3.75 mg/23 mg and 11.25 mg/69 mg dosage strengths are for titration purposes only

Dosage Modifications

Renal impairment

• Mild (≥50 mL/min): No dose adjustment required
• Moderate (30-49 mL/min) and severe (<30 mL/min): Not to exceed 7.5 mg/46 mg qDay

Hepatic impairment

• Mild (Child-Pugh 5-6): No dose adjustment required
• Moderate (Child-Pugh 7-9): Not to exceed 7.5 mg/46 mg qDay
• Severe (Child-Pugh 10-15): Avoid use

Dosing Considerations

Monitoring parameters

• Females of childbearing potential: Obtain negative pregnancy test before initiating and monthly during therapy
• Obtain blood chemistry profile that includes bicarbonate, creatinine, and potassium in all patients, and glucose in patients with type 2 diabetes on antidiabetic medication before initiating and periodically during treatment

Weight Management

Indicated as an adjunct to a reduced-calorie diet and increased physical activity for chronic weight management in adolescents aged ≥12 years with an initial BMI ≥95th percentile for age and sex

Initial: 3.75 mg/23 mg PO qDay for 14 days, THEN

Day 15: Increase to 7.5 mg/46 mg PO qDay for 12 weeks, then evaluate weight loss

After 12 weeks at 7.5 mg/46 mg: Evaluate weight loss for adolescent; if adolescent has not lost at least 3% of baseline BMI, increase to 11.25 mg/69 mg qDay for 14 days; followed by an increase to 15 mg/92 mg qDay

After 12 weeks at 15 mg/92 mg: Evaluate weight loss; if adolescent has not lost at least 5% of baseline BMI, discontinue phentermine/topiramate, as it is unlikely that the patient will achieve and sustain clinically meaningful weight loss with continued treatment

Note: 3.75 mg/23 mg and 11.25 mg/69 mg dosage strengths are for titration purposes only

Monitor rate of weight loss in pediatric patients; weight loss exceeds >2 lbs (0.9 kg)/week, consider dosage reduction

Dosage Modifications

Renal impairment

• Mild (≥50 mL/min): No dose adjustment required
• Moderate (30-49 mL/min) and severe (<30 mL/min): Not to exceed 7.5 mg/46 mg qDay

Hepatic impairment

• Mild (Child-Pugh 5-6): No dose adjustment required
• Moderate (Child-Pugh 7-9): Not to exceed 7.5 mg/46 mg qDay
• Severe (Child-Pugh 10-15): Avoid use

Dosing Considerations

Monitoring parameters

• Females of childbearing potential: Obtain negative pregnancy test before initiating and monthly during therapy
• Obtain blood chemistry profile that includes bicarbonate, creatinine, and potassium in all patients, and glucose in patients with type 2 diabetes on antidiabetic medication before initiating and periodically during treatment

Contraindicated (8)

• iobenguane I 123

  phentermine decreases effects of iobenguane I 123 by receptor binding competition. Contraindicated. If clinically appropriate, discontinue drugs that compete for NE receptor sites for at least 5 half-lives; may cause false-negative imaging results.

• isocarboxazid

  isocarboxazid increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

• linezolid

  linezolid increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

• methylphenidate

  phentermine increases effects of methylphenidate by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

• phenelzine

  phenelzine increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

• procarbazine

  procarbazine increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

• selegiline transdermal

  selegiline transdermal increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

• tranylcypromine

  tranylcypromine increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

Serious - Use Alternative (62)

• amitriptyline

  amitriptyline, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• amoxapine

  amoxapine, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• cabergoline

  cabergoline, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.

• calcium/magnesium/potassium/sodium oxybates

  calcium/magnesium/potassium/sodium oxybates, topiramate. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.

• citalopram

  citalopram, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.

• clomipramine

  clomipramine, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• desflurane

  desflurane increases toxicity of phentermine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.

• desipramine

  desipramine, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• dihydroergotamine

  topiramate will decrease the level or effect of dihydroergotamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  dihydroergotamine, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.

• dihydroergotamine intranasal

  dihydroergotamine intranasal, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.
  
  topiramate will decrease the level or effect of dihydroergotamine intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• doxapram

  doxapram increases effects of phentermine by pharmacodynamic synergism. Avoid or Use Alternate Drug. Additive pressor effect.

• dronedarone

  topiramate will decrease the level or effect of dronedarone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• doxepin

  doxepin, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• duloxetine

  duloxetine, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.

• ergoloid mesylates

  ergoloid mesylates, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.

• ergotamine

  topiramate will decrease the level or effect of ergotamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  ergotamine, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.

• erythromycin base

  topiramate will decrease the level or effect of erythromycin base by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• escitalopram

  escitalopram, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.

• erythromycin ethylsuccinate

  topiramate will decrease the level or effect of erythromycin ethylsuccinate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• erythromycin lactobionate

  topiramate will decrease the level or effect of erythromycin lactobionate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• erythromycin stearate

  topiramate will decrease the level or effect of erythromycin stearate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• ether

  ether increases toxicity of phentermine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.

• ethinylestradiol

  topiramate will decrease the level or effect of ethinylestradiol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. The efficacy of hormonal contraceptives may be reduced. Use of a nonhormonal contraceptive is recommended.

• everolimus

  topiramate will decrease the level or effect of everolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• fluoxetine

  fluoxetine, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.

• fluvoxamine

  fluvoxamine and phentermine both increase serotonin levels. Avoid or Use Alternate Drug.

• imipramine

  imipramine, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• iobenguane I 131

  phentermine will decrease the level or effect of iobenguane I 131 by Other (see comment). Avoid or Use Alternate Drug. Based on the mechanism of action of iobenguane, drugs that reduce catecholamine uptake or that deplete catecholamine stores may interfere with iobenguane uptake into cells, and thus, reduce iobenguane efficacy. Discontinue interfering drugs for at least 5 half-lives before administration of either the dosimetry or an iobenguane dose. Do not administer these drugs until at least 7 days after each iobenguane dose.

• isoflurane

  isoflurane increases toxicity of phentermine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.

• levomilnacipran

  levomilnacipran and phentermine both increase serotonin levels. Avoid or Use Alternate Drug.

• lofepramine

  lofepramine, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• lovastatin

  topiramate will decrease the level or effect of lovastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• maprotiline

  maprotiline, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• methoxyflurane

  methoxyflurane increases toxicity of phentermine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.

• methylergonovine

  methylergonovine, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.

• metoclopramide intranasal

  topiramate, metoclopramide intranasal. Either increases effects of the other by Other (see comment). Avoid or Use Alternate Drug. Comment: Avoid use of metoclopramide intranasal or interacting drug, depending on importance of drug to patient.

• milnacipran

  milnacipran, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.

• nefazodone

  nefazodone, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.

• norethindrone

  topiramate will decrease the level or effect of norethindrone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration unless benefit outweighs risk. When coadministered, hormonal contraceptives are not a reliable method of effective birth control. Concomitant use may increase incidence of menstruation associated adverse effects (amenorrhea, dysmenorrhea, menorrhagia).

• norethindrone acetate

  topiramate will decrease the level or effect of norethindrone acetate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration unless benefit outweighs risk. When coadministered, hormonal contraceptives are not a reliable method of effective birth control. Concomitant use may increase incidence of menstruation associated adverse effects (amenorrhea, dysmenorrhea, menorrhagia).

• norethindrone transdermal

  topiramate will decrease the level or effect of norethindrone transdermal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration unless benefit outweighs risk. When coadministered, hormonal contraceptives are not a reliable method of effective birth control. Concomitant use may increase incidence of menstruation associated adverse effects (amenorrhea, dysmenorrhea, menorrhagia).

• nortriptyline

  nortriptyline, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• olopatadine intranasal

  topiramate and olopatadine intranasal both increase sedation. Avoid or Use Alternate Drug. Coadministration increases risk of CNS depression, which can lead to additive impairment of psychomotor performance and cause daytime impairment.

• ozanimod

  ozanimod increases toxicity of phentermine by sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Avoid or Use Alternate Drug. Because the active metabolite of ozanimod inhibits MAO-B in vitro, there is a potential for serious adverse reactions, including hypertensive crisis. Therefore, coadministration of ozanimod with drugs that can increase norepinephrine or serotonin is not recommended. Monitor for hypertension with concomitant use.

• pacritinib

  topiramate will decrease the level or effect of pacritinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• paroxetine

  paroxetine, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.

• perampanel

  topiramate will decrease the level or effect of perampanel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Increased perampanel dose may be needed when coadministered

• protriptyline

  protriptyline, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• ranolazine

  topiramate will decrease the level or effect of ranolazine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• rasagiline

  rasagiline increases effects of phentermine by pharmacodynamic synergism. Avoid or Use Alternate Drug. Phentermine should not be administered during or within 14 days following the use of most MAOIs or drugs with MAO-inhibiting activity. Risk of acute hypertensive episode. .

• selegiline

  selegiline increases effects of phentermine by pharmacodynamic synergism. Avoid or Use Alternate Drug. Phentermine should not be administered during or within 14 days following the use of most MAOIs or drugs with MAO-inhibiting activity. Risk of acute hypertensive episode. .

• sertraline

  sertraline, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.

• sevoflurane

  sevoflurane increases toxicity of phentermine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.

• silodosin

  topiramate will decrease the level or effect of silodosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• simvastatin

  topiramate will decrease the level or effect of simvastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• sirolimus

  topiramate will decrease the level or effect of sirolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• sodium oxybate

  sodium oxybate, topiramate. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.

• tolvaptan

  topiramate will decrease the level or effect of tolvaptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• trazodone

  trazodone, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.
  
  trazodone, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.

• trimipramine

  trimipramine, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• ulipristal

  topiramate will decrease the level or effect of ulipristal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• venlafaxine

  venlafaxine, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.

Monitor Closely (338)

• acetazolamide

  topiramate, acetazolamide. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of kidney stone formation.

• acrivastine

  acrivastine and topiramate both increase sedation. Use Caution/Monitor.

• albuterol

  albuterol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and albuterol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  albuterol and phentermine both decrease sedation. Use Caution/Monitor.

• alfentanil

  alfentanil and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  alfentanil increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• almotriptan

  topiramate will decrease the level or effect of almotriptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• alprazolam

  alprazolam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• alprazolam

  topiramate will decrease the level or effect of alprazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  alprazolam and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• amiodarone

  topiramate will decrease the level or effect of amiodarone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• amitriptyline

  amitriptyline and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  amitriptyline increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  topiramate increases toxicity of amitriptyline by unspecified interaction mechanism. Use Caution/Monitor. Amitriptyline levels may increase; adjust dose based on clinical response and not on basis of plasma levels.

• amobarbital

  amobarbital increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  amobarbital and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• amoxapine

  amoxapine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  amoxapine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• apomorphine

  apomorphine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• arformoterol

  arformoterol and phentermine both decrease sedation. Use Caution/Monitor.
  
  arformoterol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• aprepitant

  topiramate will decrease the level or effect of aprepitant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• arformoterol

  topiramate increases and arformoterol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• aripiprazole

  aripiprazole increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  topiramate will decrease the level or effect of aripiprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  aripiprazole and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• armodafinil

  armodafinil and phentermine both decrease sedation. Use Caution/Monitor.
  
  topiramate increases and armodafinil decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• artemether/lumefantrine

  topiramate will decrease the level or effect of artemether/lumefantrine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• azelastine

  azelastine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• asenapine

  asenapine and topiramate both increase sedation. Use Caution/Monitor.

• asenapine transdermal

  asenapine transdermal and topiramate both increase sedation. Use Caution/Monitor.

• atogepant

  topiramate will decrease the level or effect of atogepant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• atorvastatin

  topiramate will decrease the level or effect of atorvastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• avanafil

  topiramate will decrease the level or effect of avanafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. For patients with ED, monitor response carefully because of potential for decreased effectiveness.

• avapritinib

  avapritinib and topiramate both increase sedation. Use Caution/Monitor.

• axitinib

  topiramate decreases levels of axitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• azelastine

  azelastine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• baclofen

  baclofen and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• bazedoxifene/conjugated estrogens

  topiramate will decrease the level or effect of bazedoxifene/conjugated estrogens by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• belladonna and opium

  belladonna and opium and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  belladonna and opium increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• benazepril

  phentermine decreases effects of benazepril by pharmacodynamic antagonism. Use Caution/Monitor.

• benperidol

  benperidol and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• benperidol

  benperidol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• benzhydrocodone/acetaminophen

  benzhydrocodone/acetaminophen and topiramate both increase sedation. Use Caution/Monitor.

• benzphetamine

  benzphetamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and benzphetamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  phentermine and benzphetamine both decrease sedation. Use Caution/Monitor.

• brexanolone

  brexanolone, topiramate. Either increases toxicity of the other by sedation. Use Caution/Monitor.

• bromocriptine

  bromocriptine, phentermine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Hypertension, V tach.

• brexpiprazole

  brexpiprazole and topiramate both increase sedation. Use Caution/Monitor.

• brimonidine

  brimonidine and topiramate both increase sedation. Use Caution/Monitor.

• brinzolamide

  topiramate, brinzolamide. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of kidney stone formation.

• brivaracetam

  brivaracetam and topiramate both increase sedation. Use Caution/Monitor.

• brompheniramine

  brompheniramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  brompheniramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• budesonide

  topiramate will decrease the level or effect of budesonide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• buprenorphine buccal

  buprenorphine buccal increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• buprenorphine

  buprenorphine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• buprenorphine buccal

  buprenorphine buccal and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• buprenorphine subdermal implant

  buprenorphine subdermal implant and topiramate both increase sedation. Use Caution/Monitor.

• buprenorphine transdermal

  buprenorphine transdermal and topiramate both increase sedation. Use Caution/Monitor.

• buspirone

  topiramate will decrease the level or effect of buspirone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• butabarbital

  butabarbital and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  butabarbital increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• butalbital

  butalbital and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  butalbital increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• butorphanol

  butorphanol and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  butorphanol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• caffeine

  topiramate increases and caffeine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  caffeine and phentermine both decrease sedation. Use Caution/Monitor.

• captopril

  phentermine decreases effects of captopril by pharmacodynamic antagonism. Use Caution/Monitor. Phentermine may decrease the antihypertensive effect of ACE Inhibitors.

• carbamazepine

  topiramate will decrease the level or effect of carbamazepine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  carbamazepine decreases levels of topiramate by increasing metabolism. Use Caution/Monitor.

• carbinoxamine

  carbinoxamine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  carbinoxamine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• carisoprodol

  carisoprodol and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• chloral hydrate

  chloral hydrate increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• cenobamate

  cenobamate, topiramate. Either increases effects of the other by sedation. Use Caution/Monitor.

• chloral hydrate

  chloral hydrate and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• chlordiazepoxide

  chlordiazepoxide and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  chlordiazepoxide increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• chlorpheniramine

  chlorpheniramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• chlorpromazine

  chlorpromazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  chlorpromazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  chlorpromazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• chlorzoxazone

  chlorzoxazone and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• cinnarizine

  cinnarizine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• cilostazol

  topiramate will decrease the level or effect of cilostazol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• cinacalcet

  topiramate will decrease the level or effect of cinacalcet by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• cinnarizine

  cinnarizine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• clemastine

  clemastine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  clemastine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• clobazam

  topiramate, clobazam. Other (see comment). Use Caution/Monitor. Comment: Concomitant administration can increase the potential for CNS effects (e.g., increased sedation or respiratory depression).

• clomipramine

  clomipramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• clomipramine

  clomipramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• clonazepam

  clonazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  clonazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• clopidogrel

  topiramate will increase the level or effect of clopidogrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. CYP3A4 inducers may increase the metabolism of clopidogrel to its active metabolite. Monitor patients for potential increase in antiplatelet effects when CYP3A4 inducers are used in combination with clopidogrel

• clorazepate

  clorazepate increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• clorazepate

  clorazepate and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• clozapine

  clozapine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  topiramate will decrease the level or effect of clozapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  clozapine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• codeine

  codeine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  codeine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• colchicine

  topiramate will decrease the level or effect of colchicine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• cyclizine

  cyclizine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• conivaptan

  topiramate will decrease the level or effect of conivaptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• conjugated estrogens

  topiramate will decrease the level or effect of conjugated estrogens by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• conjugated estrogens, vaginal

  topiramate will decrease the level or effect of conjugated estrogens, vaginal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• cortisone

  topiramate will decrease the level or effect of cortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• cyclizine

  cyclizine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• cyclobenzaprine

  cyclobenzaprine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• cyclosporine

  topiramate will decrease the level or effect of cyclosporine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• cyproheptadine

  cyproheptadine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  cyproheptadine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• dantrolene

  dantrolene and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• desipramine

  desipramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• daridorexant

  topiramate and daridorexant both increase sedation. Modify Therapy/Monitor Closely. Coadministration increases risk of CNS depression, which can lead to additive impairment of psychomotor performance and cause daytime impairment.

• darifenacin

  topiramate will decrease the level or effect of darifenacin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• darunavir

  topiramate will decrease the level or effect of darunavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• dasatinib

  topiramate will decrease the level or effect of dasatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• desflurane

  desflurane and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• desipramine

  desipramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• deutetrabenazine

  topiramate and deutetrabenazine both increase sedation. Use Caution/Monitor.

• dexamethasone

  topiramate will decrease the level or effect of dexamethasone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• dexchlorpheniramine

  dexchlorpheniramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  dexchlorpheniramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• dexfenfluramine

  dexfenfluramine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and dexfenfluramine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  phentermine and dexfenfluramine both decrease sedation. Use Caution/Monitor.

• dexmedetomidine

  dexmedetomidine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  dexmedetomidine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• dexmethylphenidate

  topiramate increases and dexmethylphenidate decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  dexmethylphenidate and phentermine both decrease sedation. Use Caution/Monitor.
  
  dexmethylphenidate and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• dextroamphetamine

  dextroamphetamine and phentermine both decrease sedation. Use Caution/Monitor.
  
  topiramate increases and dextroamphetamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  dextroamphetamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• dextromoramide

  dextromoramide and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  dextromoramide increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• diamorphine

  diamorphine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  diamorphine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• diazepam

  topiramate will decrease the level or effect of diazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  diazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• dichlorphenamide

  dichlorphenamide and phentermine both decrease serum potassium. Use Caution/Monitor.

• dichlorphenamide

  dichlorphenamide and topiramate both decrease serum potassium. Use Caution/Monitor.
  
  dichlorphenamide, topiramate. Either increases levels of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Both drugs can cause metabolic acidosis.

• dienogest/estradiol valerate

  topiramate will decrease the level or effect of dienogest/estradiol valerate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Advise women to use alternative method of contraception or back-up method when moderate or weak enzyme inducer is used with combination contraceptives. Back-up contraception should be continued for 28 days after discontinuing medication to ensure contraceptive reliability.

• diethylpropion

  diethylpropion and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and diethylpropion decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  phentermine and diethylpropion both decrease sedation. Use Caution/Monitor.

• difelikefalin

  difelikefalin and topiramate both increase sedation. Use Caution/Monitor.

• difenoxin hcl

  difenoxin hcl increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• difenoxin hcl

  difenoxin hcl and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• diltiazem

  phentermine will decrease the level or effect of diltiazem by pharmacodynamic antagonism. Use Caution/Monitor. Amphetamines may diminish antihypertensive effects of diltiazem. Monitor BP.
  
  topiramate will decrease the level or effect of diltiazem by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• dimenhydrinate

  dimenhydrinate increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  dimenhydrinate and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• diphenhydramine

  diphenhydramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  diphenhydramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• diphenoxylate hcl

  diphenoxylate hcl and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  diphenoxylate hcl increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• dipipanone

  dipipanone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  dipipanone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• dobutamine

  dobutamine and phentermine both decrease sedation. Use Caution/Monitor.
  
  topiramate increases and dobutamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  dobutamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• dopamine

  topiramate increases and dopamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  dopamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  phentermine and dopamine both decrease sedation. Use Caution/Monitor.

• dopexamine

  topiramate increases and dopexamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  dopexamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  dopexamine and phentermine both decrease sedation. Use Caution/Monitor.

• doxepin

  doxepin increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  doxepin and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• doxylamine

  doxylamine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• droperidol

  droperidol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• droperidol

  droperidol and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• droxidopa

  phentermine and droxidopa both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. May increase risk for supine hypertension

• eletriptan

  topiramate will decrease the level or effect of eletriptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• ephedrine

  ephedrine, phentermine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor.
  
  topiramate increases and ephedrine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  ephedrine and phentermine both decrease sedation. Use Caution/Monitor.
  
  ephedrine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• epinephrine

  epinephrine and phentermine both decrease sedation. Use Caution/Monitor.
  
  epinephrine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and epinephrine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• epinephrine inhaled

  phentermine, epinephrine inhaled. Either increases effects of the other by sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• epinephrine racemic

  topiramate increases and epinephrine racemic decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• epinephrine racemic

  epinephrine racemic and phentermine both decrease sedation. Use Caution/Monitor.
  
  epinephrine racemic and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• erlotinib

  topiramate will decrease the level or effect of erlotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• esketamine intranasal

  esketamine intranasal, topiramate. Either increases toxicity of the other by sedation. Modify Therapy/Monitor Closely.
  
  esketamine intranasal, phentermine. Either increases toxicity of the other by sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. Closely monitor blood pressure with concomitant use of esketamine nasal with stimulants. .

• estazolam

  estazolam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  estazolam and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• estradiol

  topiramate will decrease the level or effect of estradiol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• ethanol

  ethanol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• estrogens conjugated synthetic

  topiramate will decrease the level or effect of estrogens conjugated synthetic by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• estrogens esterified

  topiramate will decrease the level or effect of estrogens esterified by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Topiramate may compromise the efficacy of estrogens used for contraception or hormone replacement therapies

• estropipate

  topiramate will decrease the level or effect of estropipate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• ethanol

  ethanol and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• etonogestrel

  topiramate will decrease the level or effect of etonogestrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• etravirine

  topiramate will decrease the level or effect of etravirine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• eucalyptus

  eucalyptus and topiramate both increase sedation. Use Caution/Monitor.

• felodipine

  topiramate will decrease the level or effect of felodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• fenfluramine

  fenfluramine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and fenfluramine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  phentermine and fenfluramine both decrease sedation. Use Caution/Monitor.

• fesoterodine

  topiramate will decrease the level or effect of fesoterodine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• fluphenazine

  fluphenazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  fluphenazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• fludrocortisone

  topiramate will decrease the level or effect of fludrocortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• fluphenazine

  fluphenazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• flurazepam

  flurazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  flurazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• formoterol

  formoterol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and formoterol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  formoterol and phentermine both decrease sedation. Use Caution/Monitor.

• fosamprenavir

  topiramate will decrease the level or effect of fosamprenavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• green tea

  green tea, phentermine. Other (see comment). Use Caution/Monitor. Comment: Green tea may include caffeine. Caffeine is a CNS-stimulant and additive effects may be seen when coadministered with other CNS stimulants. Caffeine should be avoided or used cautiously.

• fosaprepitant

  topiramate will decrease the level or effect of fosaprepitant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• fosphenytoin

  fosphenytoin decreases levels of topiramate by increasing metabolism. Use Caution/Monitor.

• ganaxolone

  topiramate and ganaxolone both increase sedation. Use Caution/Monitor.

• haloperidol

  haloperidol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  haloperidol and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• hydralazine

  hydralazine, phentermine. Mechanism: pharmacodynamic antagonism. Use Caution/Monitor. Sympathomimetics can antagonize the activity of some antihypertensive agents.

• hydrocortisone

  topiramate will decrease the level or effect of hydrocortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• hydromorphone

  hydromorphone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  hydromorphone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• hydroxyprogesterone caproate (DSC)

  topiramate will decrease the level or effect of hydroxyprogesterone caproate (DSC) by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• hydroxyzine

  hydroxyzine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• hydroxyzine

  hydroxyzine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• iloperidone

  iloperidone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  topiramate will decrease the level or effect of iloperidone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  iloperidone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• imipramine

  imipramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  imipramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• indinavir

  topiramate will decrease the level or effect of indinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• ioflupane I 123

  phentermine decreases effects of ioflupane I 123 by receptor binding competition. Use Caution/Monitor. Drugs that bind to dopamine transporter receptor with high affinity may interfere with the image following ioflupane I 123 administration.

• isavuconazonium sulfate

  topiramate will decrease the level or effect of isavuconazonium sulfate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• isoproterenol

  isoproterenol and phentermine both decrease sedation. Use Caution/Monitor.
  
  topiramate increases and isoproterenol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  isoproterenol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• ketamine

  ketamine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• ketotifen, ophthalmic

  ketotifen, ophthalmic increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• ketotifen, ophthalmic

  ketotifen, ophthalmic and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• lacosamide

  topiramate increases toxicity of lacosamide by Other (see comment). Use Caution/Monitor. Comment: Coadministration of lacosamide with sodium channel-blocking antiseizure drugs may increase the risk for AV block, bradycardia, or ventricular tachyarrhythmias. Monitor ECG before beginning lacosamide and after lacosamide is titrated to steady-state.

• lapatinib

  topiramate will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• lasmiditan

  lasmiditan, topiramate. Either increases effects of the other by sedation. Use Caution/Monitor. Coadministration of lasmiditan and other CNS depressant drugs, including alcohol have not been evaluated in clinical studies. Lasmiditan may cause sedation, as well as other cognitive and/or neuropsychiatric adverse reactions.

• lemborexant

  lemborexant will increase the level or effect of topiramate by sedation. Modify Therapy/Monitor Closely. Dosage adjustment may be necessary if lemborexant is coadministered with other CNS depressants because of potentially additive effects.

• levalbuterol

  topiramate increases and levalbuterol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  levalbuterol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  levalbuterol and phentermine both decrease sedation. Use Caution/Monitor.

• levonorgestrel intrauterine

  topiramate decreases levels of levonorgestrel intrauterine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• levorphanol

  levorphanol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• levonorgestrel oral

  topiramate decreases levels of levonorgestrel oral by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• levonorgestrel oral/ethinylestradiol/ferrous bisglycinate

  topiramate will decrease the level or effect of levonorgestrel oral/ethinylestradiol/ferrous bisglycinate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. The efficacy of hormonal contraceptives may be reduced. Use an alternative method of contraception or a backup method when enzyme inducers are used with combined hormonal contraceptives (CHCs), and continue backup contraception for 28 days after discontinuing enzyme inducer to ensure contraceptive reliability.

• levorphanol

  levorphanol and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• linagliptin

  topiramate will increase the level or effect of linagliptin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Use of alternative treatments is strongly recommended when linagliptin is to be administered with a CYP3A4 inducer

• lisdexamfetamine

  lisdexamfetamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  lisdexamfetamine and phentermine both decrease sedation. Use Caution/Monitor.
  
  topiramate increases and lisdexamfetamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• lithium

  topiramate increases levels of lithium by unspecified interaction mechanism. Use Caution/Monitor. Increase in lithium exposure may occur with doses of up to 600 mg/day; monitor lithium levels when coadministered with high-dose topiramate .

• lofepramine

  lofepramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• lofepramine

  lofepramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• lofexidine

  lofexidine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  lofexidine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• lopinavir

  topiramate will decrease the level or effect of lopinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• loprazolam

  loprazolam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• loprazolam

  loprazolam and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• loratadine

  topiramate will decrease the level or effect of loratadine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• lorazepam

  lorazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  lorazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• lormetazepam

  lormetazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  lormetazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• loxapine

  loxapine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  loxapine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• loxapine inhaled

  loxapine inhaled and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  loxapine inhaled increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• lumefantrine

  topiramate will decrease the level or effect of lumefantrine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• maprotiline

  maprotiline increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• lurasidone

  lurasidone, topiramate. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: Potential for increased CNS depressant effects when used concurrently; monitor for increased adverse effects and toxicity.

• maprotiline

  maprotiline and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• maraviroc

  topiramate will decrease the level or effect of maraviroc by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• marijuana

  marijuana and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  marijuana increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• mavacamten

  topiramate will increase the level or effect of mavacamten by affecting hepatic enzyme CYP2C19 metabolism. Modify Therapy/Monitor Closely. Inititiation of weak CYP2C19 inhibitors may require decreased mavacamten dose.

• melatonin

  melatonin increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• melatonin

  melatonin and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• meperidine

  meperidine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  meperidine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• meprobamate

  meprobamate increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  meprobamate and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• mestranol

  topiramate will decrease the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• metaproterenol

  metaproterenol and phentermine both decrease sedation. Use Caution/Monitor.
  
  metaproterenol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• metaproterenol

  topiramate increases and metaproterenol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• metaxalone

  metaxalone and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• metformin

  phentermine decreases effects of metformin by pharmacodynamic antagonism. Use Caution/Monitor. Patient should be closely observed for loss of blood glucose control; when drugs are withdrawn from a patient receiving metformin, patient should be observed closely for hypoglycemia.
  
  topiramate increases toxicity of metformin by Other (see comment). Use Caution/Monitor. Comment: Decreases serum bicarbonate and induce non-anion gap, hyperchloremic metabolic acidosis.

• methadone

  topiramate will decrease the level or effect of methadone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  methadone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  methadone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• methamphetamine

  methamphetamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  methamphetamine and phentermine both decrease sedation. Use Caution/Monitor.

• methazolamide

  topiramate, methazolamide. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of kidney stone formation.

• methyldopa

  methyldopa increases effects of phentermine by unknown mechanism. Use Caution/Monitor.

• methocarbamol

  methocarbamol and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• methylenedioxymethamphetamine

  methylenedioxymethamphetamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and methylenedioxymethamphetamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  methylenedioxymethamphetamine and phentermine both decrease sedation. Use Caution/Monitor.

• methylphenidate transdermal

  methylphenidate transdermal will increase the level or effect of topiramate by decreasing metabolism. Modify Therapy/Monitor Closely. Consider decreasing the dose of these drugs when given coadministered with methylphenidate. Monitor for drug toxiticities when initiating or discontinuing methylphenidate.

• midazolam

  midazolam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• methylprednisolone

  topiramate will decrease the level or effect of methylprednisolone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• midazolam

  topiramate will decrease the level or effect of midazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  midazolam and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• midazolam intranasal

  midazolam intranasal, topiramate. Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Concomitant use of barbiturates, alcohol, or other CNS depressants may increase the risk of hypoventilation, airway obstruction, desaturation, or apnea and may contribute to profound and/or prolonged drug effect.

• midodrine

  topiramate increases and midodrine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  phentermine and midodrine both decrease sedation. Use Caution/Monitor.
  
  midodrine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• mirtazapine

  mirtazapine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  mirtazapine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• modafinil

  modafinil and phentermine both decrease sedation. Use Caution/Monitor.
  
  topiramate increases and modafinil decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• morphine

  morphine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  morphine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• motherwort

  motherwort and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  motherwort increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• moxonidine

  moxonidine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  moxonidine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• nabilone

  nabilone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  nabilone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• nalbuphine

  nalbuphine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  nalbuphine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• nelfinavir

  topiramate will decrease the level or effect of nelfinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• norepinephrine

  norepinephrine and phentermine both decrease sedation. Use Caution/Monitor.
  
  norepinephrine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• nicardipine

  topiramate will decrease the level or effect of nicardipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• nilotinib

  topiramate will decrease the level or effect of nilotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• nisoldipine

  topiramate will decrease the level or effect of nisoldipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• norepinephrine

  topiramate increases and norepinephrine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• nortriptyline

  nortriptyline and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  nortriptyline increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• olanzapine

  olanzapine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  olanzapine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• opium tincture

  opium tincture and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  opium tincture increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• orlistat

  orlistat decreases levels of topiramate by inhibition of GI absorption. Applies only to oral form of both agents. Modify Therapy/Monitor Closely. Risk of convulsions.

• oxazepam

  oxazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• orphenadrine

  orphenadrine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• oxazepam

  oxazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• oxycodone

  oxycodone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  oxycodone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• oxymorphone

  oxymorphone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  oxymorphone and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• oxytocin

  oxytocin increases effects of phentermine by pharmacodynamic synergism. Use Caution/Monitor.

• paliperidone

  paliperidone and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• paliperidone

  paliperidone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• papaveretum

  papaveretum and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  papaveretum increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• papaverine

  papaverine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• pentazocine

  pentazocine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• pazopanib

  topiramate will decrease the level or effect of pazopanib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• pentazocine

  pentazocine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• pentobarbital

  pentobarbital and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  pentobarbital increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• perphenazine

  perphenazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  perphenazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  perphenazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• phendimetrazine

  topiramate increases and phendimetrazine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  phendimetrazine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  phentermine and phendimetrazine both decrease sedation. Use Caution/Monitor.

• phenobarbital

  phenobarbital and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  phenobarbital increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• phentermine

  topiramate increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• phenylephrine

  phentermine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  phentermine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• phenylephrine

  topiramate increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• phenylephrine PO

  topiramate increases and phenylephrine PO decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely. .
  
  phentermine and phenylephrine PO both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  phentermine and phenylephrine PO both decrease sedation. Use Caution/Monitor.

• phenytoin

  phenytoin decreases levels of topiramate by increasing metabolism. Use Caution/Monitor.

• pholcodine

  pholcodine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• pholcodine

  pholcodine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• pimozide

  pimozide and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  pimozide increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• pirbuterol

  pirbuterol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  pirbuterol and phentermine both decrease sedation. Use Caution/Monitor.
  
  topiramate increases and pirbuterol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• prednisone

  topiramate will decrease the level or effect of prednisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• primidone

  primidone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• primidone

  primidone and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• prochlorperazine

  prochlorperazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  prochlorperazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  prochlorperazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• promazine

  promazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• promethazine

  promethazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• promethazine

  promethazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  promethazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• propofol

  propofol and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• propylhexedrine

  phentermine and propylhexedrine both decrease sedation. Use Caution/Monitor.
  
  phentermine and propylhexedrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and propylhexedrine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• protriptyline

  protriptyline and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  protriptyline increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• pseudoephedrine

  phentermine and pseudoephedrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• quazepam

  quazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• quazepam

  quazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• quetiapine

  quetiapine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  topiramate will decrease the level or effect of quetiapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  quetiapine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• quinidine

  topiramate will decrease the level or effect of quinidine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• risperidone

  risperidone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• ramelteon

  ramelteon and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• repaglinide

  topiramate will decrease the level or effect of repaglinide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• risperidone

  risperidone and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• ritonavir

  topiramate will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• romidepsin

  topiramate will decrease the level or effect of romidepsin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• sage

  sage and topiramate both increase sedation. Use Caution/Monitor.

• salmeterol

  salmeterol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and salmeterol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  salmeterol and phentermine both decrease sedation. Use Caution/Monitor.

• saquinavir

  topiramate will decrease the level or effect of saquinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• scullcap

  scullcap increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• scullcap

  scullcap and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• secobarbital

  secobarbital increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  secobarbital and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• serdexmethylphenidate/dexmethylphenidate

  serdexmethylphenidate/dexmethylphenidate and phentermine both decrease sedation. Use Caution/Monitor.
  
  serdexmethylphenidate/dexmethylphenidate and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• sevelamer

  sevelamer decreases levels of topiramate by increasing elimination. Use Caution/Monitor.

• sevoflurane

  sevoflurane and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• shepherd's purse

  shepherd's purse and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  shepherd's purse increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• solifenacin

  topiramate will decrease the level or effect of solifenacin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• solriamfetol

  phentermine and solriamfetol both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• stiripentol

  stiripentol, topiramate. Either increases effects of the other by sedation. Use Caution/Monitor. Concomitant use stiripentol with other CNS depressants, including alcohol, may increase the risk of sedation and somnolence.

• sufentanil

  sufentanil increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  sufentanil and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• sunitinib

  topiramate will decrease the level or effect of sunitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tapentadol

  tapentadol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• tacrolimus

  topiramate will decrease the level or effect of tacrolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tadalafil

  topiramate will decrease the level or effect of tadalafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tapentadol

  tapentadol and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• tazemetostat

  topiramate will decrease the level or effect of tazemetostat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• temazepam

  temazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  temazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• temsirolimus

  topiramate will decrease the level or effect of temsirolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• terbutaline

  terbutaline and phentermine both decrease sedation. Use Caution/Monitor.
  
  terbutaline and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• terbutaline

  topiramate increases and terbutaline decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• theophylline

  topiramate will decrease the level or effect of theophylline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• thioridazine

  thioridazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  thioridazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• thiothixene

  thiothixene and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  thiothixene increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• tipranavir

  topiramate will decrease the level or effect of tipranavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• topiramate

  topiramate increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• tobramycin inhaled

  tobramycin inhaled and topiramate both increase nephrotoxicity and/or ototoxicity. Modify Therapy/Monitor Closely. Avoid concurrent or sequential use to decrease risk for ototoxicity

• tolterodine

  topiramate will decrease the level or effect of tolterodine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tramadol

  tramadol and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  tramadol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• trazodone

  trazodone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  topiramate will decrease the level or effect of trazodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  trazodone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• triamcinolone acetonide injectable suspension

  topiramate will decrease the level or effect of triamcinolone acetonide injectable suspension by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• triazolam

  triazolam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• triazolam

  topiramate will decrease the level or effect of triazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  triazolam and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• triclofos

  triclofos and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  triclofos increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• trifluoperazine

  trifluoperazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  trifluoperazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  trifluoperazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• trimipramine

  trimipramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  trimipramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• triprolidine

  triprolidine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  triprolidine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• ubrogepant

  topiramate will decrease the level or effect of ubrogepant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Dose adjustment is recommended with concomitant use of ubrogepant and moderate and weak CYP3A4 inducers. (see Dosage Modifications)

• xylometazoline

  phentermine and xylometazoline both decrease sedation. Use Caution/Monitor.
  
  phentermine and xylometazoline both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• valproic acid

  valproic acid, topiramate. Either increases toxicity of the other by unknown mechanism. Use Caution/Monitor. Risk of hyperammonemia with or without encephalopathy; pts. with inborn errors of metabolism may be at greater risk. S/S: altered LOC, lethargy, vomiting.

• vardenafil

  topiramate will decrease the level or effect of vardenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• verapamil

  topiramate will decrease the level or effect of verapamil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• xylometazoline

  topiramate increases and xylometazoline decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• yohimbine

  phentermine and yohimbine both decrease sedation. Use Caution/Monitor.
  
  phentermine and yohimbine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and yohimbine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• ziconotide

  ziconotide increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  topiramate and ziconotide both increase sedation. Modify Therapy/Monitor Closely.

• ziprasidone

  ziprasidone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  ziprasidone and topiramate both increase sedation. Modify Therapy/Monitor Closely.

Minor (71)

• acetaminophen

  topiramate decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.

• acetaminophen IV

  topiramate decreases levels of acetaminophen IV by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.

• acetaminophen rectal

  topiramate decreases levels of acetaminophen rectal by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.

• alfentanil

  topiramate will decrease the level or effect of alfentanil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• alfuzosin

  topiramate will decrease the level or effect of alfuzosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• alosetron

  topiramate will decrease the level or effect of alosetron by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• amantadine

  amantadine, phentermine. Either increases effects of the other by pharmacodynamic synergism. Minor/Significance Unknown. Potential for additive CNS stimulation.

• American ginseng

  American ginseng increases effects of phentermine by pharmacodynamic synergism. Minor/Significance Unknown.

• amobarbital

  amobarbital decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown.

• armodafinil

  topiramate will decrease the level or effect of armodafinil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• atazanavir

  topiramate will decrease the level or effect of atazanavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• atracurium

  topiramate decreases effects of atracurium by pharmacodynamic antagonism. Minor/Significance Unknown.

• biotin

  topiramate decreases levels of biotin by unspecified interaction mechanism. Minor/Significance Unknown. Biotin supplementation may be necessary.

• bortezomib

  topiramate will decrease the level or effect of bortezomib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown. Caution is advised with concurrent use.

• bosentan

  topiramate will decrease the level or effect of bosentan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• butabarbital

  butabarbital decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown.

• butalbital

  butalbital decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown.

• cevimeline

  topiramate will decrease the level or effect of cevimeline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• cisatracurium

  topiramate decreases effects of cisatracurium by pharmacodynamic antagonism. Minor/Significance Unknown.

• clarithromycin

  topiramate will decrease the level or effect of clarithromycin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• clomipramine

  topiramate will decrease the level or effect of clomipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• cyanocobalamin

  topiramate decreases levels of cyanocobalamin by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• dapsone

  topiramate will decrease the level or effect of dapsone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• desmopressin

  desmopressin increases effects of phentermine by pharmacodynamic synergism. Minor/Significance Unknown.

• dexmethylphenidate

  dexmethylphenidate increases effects of topiramate by decreasing metabolism. Minor/Significance Unknown.

• digoxin

  topiramate decreases levels of digoxin by unspecified interaction mechanism. Minor/Significance Unknown.

• disopyramide

  topiramate will decrease the level or effect of disopyramide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• donepezil

  topiramate will decrease the level or effect of donepezil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• dutasteride

  topiramate will decrease the level or effect of dutasteride by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• efavirenz

  topiramate will decrease the level or effect of efavirenz by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• eplerenone

  topiramate will decrease the level or effect of eplerenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• ethotoin

  topiramate increases levels of ethotoin by decreasing metabolism. Minor/Significance Unknown.
  
  ethotoin decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown.

• eucalyptus

  eucalyptus increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Minor/Significance Unknown.
  
  topiramate will decrease the level or effect of eucalyptus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• finasteride

  topiramate will decrease the level or effect of finasteride by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• guarana

  guarana increases effects of phentermine by pharmacodynamic synergism. Minor/Significance Unknown.

• fosphenytoin

  topiramate increases levels of fosphenytoin by decreasing metabolism. Minor/Significance Unknown.

• galantamine

  topiramate will decrease the level or effect of galantamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• glyburide

  topiramate will decrease the level or effect of glyburide by unknown mechanism. Minor/Significance Unknown. Effect in glycemic control is likely small.

• imatinib

  topiramate will decrease the level or effect of imatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• imipramine

  topiramate will decrease the level or effect of imipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• incobotulinumtoxinA

  topiramate decreases effects of incobotulinumtoxinA by pharmacodynamic antagonism. Minor/Significance Unknown.

• isradipine

  topiramate will decrease the level or effect of isradipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• itraconazole

  topiramate will decrease the level or effect of itraconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• ketoconazole

  topiramate will decrease the level or effect of ketoconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• levocarnitine

  topiramate decreases levels of levocarnitine by unspecified interaction mechanism. Minor/Significance Unknown.

• levoketoconazole

  topiramate will decrease the level or effect of levoketoconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• montelukast

  topiramate will decrease the level or effect of montelukast by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• nifedipine

  topiramate will decrease the level or effect of nifedipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• nimodipine

  topiramate will decrease the level or effect of nimodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• nitrendipine

  topiramate will decrease the level or effect of nitrendipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• onabotulinumtoxinA

  topiramate decreases effects of onabotulinumtoxinA by pharmacodynamic antagonism. Minor/Significance Unknown.

• ondansetron

  topiramate will decrease the level or effect of ondansetron by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• oxybutynin

  topiramate will decrease the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• paclitaxel

  topiramate will decrease the level or effect of paclitaxel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• paclitaxel protein bound

  topiramate will decrease the level or effect of paclitaxel protein bound by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• pancuronium

  topiramate decreases effects of pancuronium by pharmacodynamic antagonism. Minor/Significance Unknown.

• parecoxib

  topiramate will decrease the level or effect of parecoxib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• pentobarbital

  pentobarbital decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown.

• phenobarbital

  phenobarbital decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown.

• phenytoin

  topiramate increases levels of phenytoin by decreasing metabolism. Minor/Significance Unknown.

• pimozide

  topiramate will decrease the level or effect of pimozide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• pioglitazone

  topiramate will decrease the level or effect of pioglitazone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• primidone

  primidone decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown.

• propafenone

  topiramate will decrease the level or effect of propafenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• quinine

  topiramate will decrease the level or effect of quinine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• ramelteon

  topiramate will decrease the level or effect of ramelteon by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• rapacuronium

  topiramate decreases effects of rapacuronium by pharmacodynamic antagonism. Minor/Significance Unknown.

• rocuronium

  topiramate decreases effects of rocuronium by pharmacodynamic antagonism. Minor/Significance Unknown.

• sage

  sage increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Minor/Significance Unknown.
  
  sage decreases effects of topiramate by pharmacodynamic antagonism. Minor/Significance Unknown. Theoretical interaction; some species of sage may cause convulsions.

• saxagliptin

  topiramate will decrease the level or effect of saxagliptin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• yerba mate

  yerba mate increases effects of phentermine by pharmacodynamic synergism. Minor/Significance Unknown.

• acetaminophen

  Minor (1)topiramate decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.

• acetaminophen IV

  Minor (1)topiramate decreases levels of acetaminophen IV by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.

• acetaminophen rectal

  Minor (1)topiramate decreases levels of acetaminophen rectal by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.

• acetazolamide

  Monitor Closely (1)topiramate, acetazolamide. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of kidney stone formation.

• acrivastine

  Monitor Closely (1)acrivastine and topiramate both increase sedation. Use Caution/Monitor.

• albuterol

  Monitor Closely (3)albuterol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and albuterol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  albuterol and phentermine both decrease sedation. Use Caution/Monitor.

• alfentanil

  Monitor Closely (2)alfentanil and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  alfentanil increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)topiramate will decrease the level or effect of alfentanil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• alfuzosin

  Minor (1)topiramate will decrease the level or effect of alfuzosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• almotriptan

  Monitor Closely (1)topiramate will decrease the level or effect of almotriptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• alosetron

  Minor (1)topiramate will decrease the level or effect of alosetron by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• alprazolam

  Monitor Closely (3)topiramate will decrease the level or effect of alprazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  alprazolam and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  alprazolam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• amantadine

  Minor (1)amantadine, phentermine. Either increases effects of the other by pharmacodynamic synergism. Minor/Significance Unknown. Potential for additive CNS stimulation.

• American ginseng

  Minor (1)American ginseng increases effects of phentermine by pharmacodynamic synergism. Minor/Significance Unknown.

• amiodarone

  Monitor Closely (1)topiramate will decrease the level or effect of amiodarone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• amitriptyline

  Monitor Closely (3)amitriptyline and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  amitriptyline increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  topiramate increases toxicity of amitriptyline by unspecified interaction mechanism. Use Caution/Monitor. Amitriptyline levels may increase; adjust dose based on clinical response and not on basis of plasma levels.Serious - Use Alternative (1)amitriptyline, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• amobarbital

  Monitor Closely (2)amobarbital increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  amobarbital and topiramate both increase sedation. Modify Therapy/Monitor Closely.Minor (1)amobarbital decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown.

• amoxapine

  Monitor Closely (2)amoxapine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  amoxapine and topiramate both increase sedation. Modify Therapy/Monitor Closely.Serious - Use Alternative (1)amoxapine, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• apomorphine

  Monitor Closely (1)apomorphine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• aprepitant

  Monitor Closely (1)topiramate will decrease the level or effect of aprepitant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• arformoterol

  Monitor Closely (3)arformoterol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and arformoterol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  arformoterol and phentermine both decrease sedation. Use Caution/Monitor.

• aripiprazole

  Monitor Closely (3)aripiprazole increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  topiramate will decrease the level or effect of aripiprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  aripiprazole and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• armodafinil

  Monitor Closely (2)armodafinil and phentermine both decrease sedation. Use Caution/Monitor.
  
  topiramate increases and armodafinil decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.Minor (1)topiramate will decrease the level or effect of armodafinil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• artemether/lumefantrine

  Monitor Closely (1)topiramate will decrease the level or effect of artemether/lumefantrine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• asenapine

  Monitor Closely (1)asenapine and topiramate both increase sedation. Use Caution/Monitor.

• asenapine transdermal

  Monitor Closely (1)asenapine transdermal and topiramate both increase sedation. Use Caution/Monitor.

• atazanavir

  Minor (1)topiramate will decrease the level or effect of atazanavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• atogepant

  Monitor Closely (1)topiramate will decrease the level or effect of atogepant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• atorvastatin

  Monitor Closely (1)topiramate will decrease the level or effect of atorvastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• atracurium

  Minor (1)topiramate decreases effects of atracurium by pharmacodynamic antagonism. Minor/Significance Unknown.

• avanafil

  Monitor Closely (1)topiramate will decrease the level or effect of avanafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. For patients with ED, monitor response carefully because of potential for decreased effectiveness.

• avapritinib

  Monitor Closely (1)avapritinib and topiramate both increase sedation. Use Caution/Monitor.

• axitinib

  Monitor Closely (1)topiramate decreases levels of axitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• azelastine

  Monitor Closely (2)azelastine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  azelastine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• baclofen

  Monitor Closely (1)baclofen and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• bazedoxifene/conjugated estrogens

  Monitor Closely (1)topiramate will decrease the level or effect of bazedoxifene/conjugated estrogens by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• belladonna and opium

  Monitor Closely (2)belladonna and opium and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  belladonna and opium increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• benazepril

  Monitor Closely (1)phentermine decreases effects of benazepril by pharmacodynamic antagonism. Use Caution/Monitor.

• benperidol

  Monitor Closely (2)benperidol and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  benperidol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• benzhydrocodone/acetaminophen

  Monitor Closely (1)benzhydrocodone/acetaminophen and topiramate both increase sedation. Use Caution/Monitor.

• benzphetamine

  Monitor Closely (3)benzphetamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and benzphetamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  phentermine and benzphetamine both decrease sedation. Use Caution/Monitor.

• biotin

  Minor (1)topiramate decreases levels of biotin by unspecified interaction mechanism. Minor/Significance Unknown. Biotin supplementation may be necessary.

• bortezomib

  Minor (1)topiramate will decrease the level or effect of bortezomib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown. Caution is advised with concurrent use.

• bosentan

  Minor (1)topiramate will decrease the level or effect of bosentan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• brexanolone

  Monitor Closely (1)brexanolone, topiramate. Either increases toxicity of the other by sedation. Use Caution/Monitor.

• brexpiprazole

  Monitor Closely (1)brexpiprazole and topiramate both increase sedation. Use Caution/Monitor.

• brimonidine

  Monitor Closely (1)brimonidine and topiramate both increase sedation. Use Caution/Monitor.

• brinzolamide

  Monitor Closely (1)topiramate, brinzolamide. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of kidney stone formation.

• brivaracetam

  Monitor Closely (1)brivaracetam and topiramate both increase sedation. Use Caution/Monitor.

• bromocriptine

  Monitor Closely (1)bromocriptine, phentermine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Hypertension, V tach.

• brompheniramine

  Monitor Closely (2)brompheniramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  brompheniramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• budesonide

  Monitor Closely (1)topiramate will decrease the level or effect of budesonide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• buprenorphine

  Monitor Closely (1)buprenorphine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• buprenorphine buccal

  Monitor Closely (2)buprenorphine buccal increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  buprenorphine buccal and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• buprenorphine subdermal implant

  Monitor Closely (1)buprenorphine subdermal implant and topiramate both increase sedation. Use Caution/Monitor.

• buprenorphine transdermal

  Monitor Closely (1)buprenorphine transdermal and topiramate both increase sedation. Use Caution/Monitor.

• buspirone

  Monitor Closely (1)topiramate will decrease the level or effect of buspirone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• butabarbital

  Monitor Closely (2)butabarbital and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  butabarbital increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)butabarbital decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown.

• butalbital

  Monitor Closely (2)butalbital and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  butalbital increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)butalbital decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown.

• butorphanol

  Monitor Closely (2)butorphanol and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  butorphanol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• cabergoline

  Serious - Use Alternative (1)cabergoline, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.

• caffeine

  Monitor Closely (2)topiramate increases and caffeine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  caffeine and phentermine both decrease sedation. Use Caution/Monitor.

• calcium/magnesium/potassium/sodium oxybates

  Serious - Use Alternative (1)calcium/magnesium/potassium/sodium oxybates, topiramate. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.

• captopril

  Monitor Closely (1)phentermine decreases effects of captopril by pharmacodynamic antagonism. Use Caution/Monitor. Phentermine may decrease the antihypertensive effect of ACE Inhibitors.

• carbamazepine

  Monitor Closely (2)topiramate will decrease the level or effect of carbamazepine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  carbamazepine decreases levels of topiramate by increasing metabolism. Use Caution/Monitor.

• carbinoxamine

  Monitor Closely (2)carbinoxamine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  carbinoxamine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• carisoprodol

  Monitor Closely (1)carisoprodol and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• cenobamate

  Monitor Closely (1)cenobamate, topiramate. Either increases effects of the other by sedation. Use Caution/Monitor.

• cevimeline

  Minor (1)topiramate will decrease the level or effect of cevimeline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• chloral hydrate

  Monitor Closely (2)chloral hydrate and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  chloral hydrate increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• chlordiazepoxide

  Monitor Closely (2)chlordiazepoxide and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  chlordiazepoxide increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• chlorpheniramine

  Monitor Closely (2)chlorpheniramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  chlorpheniramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• chlorpromazine

  Monitor Closely (3)chlorpromazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  chlorpromazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  chlorpromazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• chlorzoxazone

  Monitor Closely (1)chlorzoxazone and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• cilostazol

  Monitor Closely (1)topiramate will decrease the level or effect of cilostazol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• cinacalcet

  Monitor Closely (1)topiramate will decrease the level or effect of cinacalcet by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• cinnarizine

  Monitor Closely (2)cinnarizine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  cinnarizine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• cisatracurium

  Minor (1)topiramate decreases effects of cisatracurium by pharmacodynamic antagonism. Minor/Significance Unknown.

• citalopram

  Serious - Use Alternative (1)citalopram, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.

• clarithromycin

  Minor (1)topiramate will decrease the level or effect of clarithromycin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• clemastine

  Monitor Closely (2)clemastine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  clemastine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• clobazam

  Monitor Closely (1)topiramate, clobazam. Other (see comment). Use Caution/Monitor. Comment: Concomitant administration can increase the potential for CNS effects (e.g., increased sedation or respiratory depression).

• clomipramine

  Monitor Closely (2)clomipramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  clomipramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)topiramate will decrease the level or effect of clomipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.Serious - Use Alternative (1)clomipramine, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• clonazepam

  Monitor Closely (2)clonazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  clonazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• clopidogrel

  Monitor Closely (1)topiramate will increase the level or effect of clopidogrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. CYP3A4 inducers may increase the metabolism of clopidogrel to its active metabolite. Monitor patients for potential increase in antiplatelet effects when CYP3A4 inducers are used in combination with clopidogrel

• clorazepate

  Monitor Closely (2)clorazepate and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  clorazepate increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• clozapine

  Monitor Closely (3)clozapine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  topiramate will decrease the level or effect of clozapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  clozapine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• codeine

  Monitor Closely (2)codeine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  codeine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• colchicine

  Monitor Closely (1)topiramate will decrease the level or effect of colchicine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• conivaptan

  Monitor Closely (1)topiramate will decrease the level or effect of conivaptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• conjugated estrogens

  Monitor Closely (1)topiramate will decrease the level or effect of conjugated estrogens by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• conjugated estrogens, vaginal

  Monitor Closely (1)topiramate will decrease the level or effect of conjugated estrogens, vaginal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• cortisone

  Monitor Closely (1)topiramate will decrease the level or effect of cortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• cyanocobalamin

  Minor (1)topiramate decreases levels of cyanocobalamin by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.

• cyclizine

  Monitor Closely (2)cyclizine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  cyclizine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• cyclobenzaprine

  Monitor Closely (1)cyclobenzaprine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• cyclosporine

  Monitor Closely (1)topiramate will decrease the level or effect of cyclosporine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• cyproheptadine

  Monitor Closely (2)cyproheptadine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  cyproheptadine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• dantrolene

  Monitor Closely (1)dantrolene and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• dapsone

  Minor (1)topiramate will decrease the level or effect of dapsone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• daridorexant

  Monitor Closely (1)topiramate and daridorexant both increase sedation. Modify Therapy/Monitor Closely. Coadministration increases risk of CNS depression, which can lead to additive impairment of psychomotor performance and cause daytime impairment.

• darifenacin

  Monitor Closely (1)topiramate will decrease the level or effect of darifenacin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• darunavir

  Monitor Closely (1)topiramate will decrease the level or effect of darunavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• dasatinib

  Monitor Closely (1)topiramate will decrease the level or effect of dasatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• desflurane

  Monitor Closely (1)desflurane and topiramate both increase sedation. Modify Therapy/Monitor Closely.Serious - Use Alternative (1)desflurane increases toxicity of phentermine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.

• desipramine

  Monitor Closely (2)desipramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  desipramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Serious - Use Alternative (1)desipramine, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• desmopressin

  Minor (1)desmopressin increases effects of phentermine by pharmacodynamic synergism. Minor/Significance Unknown.

• deutetrabenazine

  Monitor Closely (1)topiramate and deutetrabenazine both increase sedation. Use Caution/Monitor.

• dexamethasone

  Monitor Closely (1)topiramate will decrease the level or effect of dexamethasone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• dexchlorpheniramine

  Monitor Closely (2)dexchlorpheniramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  dexchlorpheniramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• dexfenfluramine

  Monitor Closely (3)dexfenfluramine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and dexfenfluramine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  phentermine and dexfenfluramine both decrease sedation. Use Caution/Monitor.

• dexmedetomidine

  Monitor Closely (2)dexmedetomidine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  dexmedetomidine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• dexmethylphenidate

  Monitor Closely (3)topiramate increases and dexmethylphenidate decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  dexmethylphenidate and phentermine both decrease sedation. Use Caution/Monitor.
  
  dexmethylphenidate and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.Minor (1)dexmethylphenidate increases effects of topiramate by decreasing metabolism. Minor/Significance Unknown.

• dextroamphetamine

  Monitor Closely (3)dextroamphetamine and phentermine both decrease sedation. Use Caution/Monitor.
  
  topiramate increases and dextroamphetamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  dextroamphetamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• dextromoramide

  Monitor Closely (2)dextromoramide and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  dextromoramide increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• diamorphine

  Monitor Closely (2)diamorphine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  diamorphine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• diazepam

  Monitor Closely (2)topiramate will decrease the level or effect of diazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  diazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• dichlorphenamide

  Monitor Closely (3)dichlorphenamide, topiramate. Either increases levels of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Both drugs can cause metabolic acidosis.
  
  dichlorphenamide and topiramate both decrease serum potassium. Use Caution/Monitor.
  
  dichlorphenamide and phentermine both decrease serum potassium. Use Caution/Monitor.

• dienogest/estradiol valerate

  Monitor Closely (1)topiramate will decrease the level or effect of dienogest/estradiol valerate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Advise women to use alternative method of contraception or back-up method when moderate or weak enzyme inducer is used with combination contraceptives. Back-up contraception should be continued for 28 days after discontinuing medication to ensure contraceptive reliability.

• diethylpropion

  Monitor Closely (3)diethylpropion and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and diethylpropion decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  phentermine and diethylpropion both decrease sedation. Use Caution/Monitor.

• difelikefalin

  Monitor Closely (1)difelikefalin and topiramate both increase sedation. Use Caution/Monitor.

• difenoxin hcl

  Monitor Closely (2)difenoxin hcl and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  difenoxin hcl increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• digoxin

  Minor (1)topiramate decreases levels of digoxin by unspecified interaction mechanism. Minor/Significance Unknown.

• dihydroergotamine

  Serious - Use Alternative (2)topiramate will decrease the level or effect of dihydroergotamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  dihydroergotamine, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.

• dihydroergotamine intranasal

  Serious - Use Alternative (2)dihydroergotamine intranasal, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.
  
  topiramate will decrease the level or effect of dihydroergotamine intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• diltiazem

  Monitor Closely (2)phentermine will decrease the level or effect of diltiazem by pharmacodynamic antagonism. Use Caution/Monitor. Amphetamines may diminish antihypertensive effects of diltiazem. Monitor BP.
  
  topiramate will decrease the level or effect of diltiazem by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• dimenhydrinate

  Monitor Closely (2)dimenhydrinate increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  dimenhydrinate and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• diphenhydramine

  Monitor Closely (2)diphenhydramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  diphenhydramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• diphenoxylate hcl

  Monitor Closely (2)diphenoxylate hcl and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  diphenoxylate hcl increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• dipipanone

  Monitor Closely (2)dipipanone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  dipipanone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• disopyramide

  Minor (1)topiramate will decrease the level or effect of disopyramide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• dobutamine

  Monitor Closely (3)dobutamine and phentermine both decrease sedation. Use Caution/Monitor.
  
  topiramate increases and dobutamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  dobutamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• donepezil

  Minor (1)topiramate will decrease the level or effect of donepezil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• dopamine

  Monitor Closely (3)topiramate increases and dopamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  dopamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  phentermine and dopamine both decrease sedation. Use Caution/Monitor.

• dopexamine

  Monitor Closely (3)topiramate increases and dopexamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  dopexamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  dopexamine and phentermine both decrease sedation. Use Caution/Monitor.

• doxapram

  Serious - Use Alternative (1)doxapram increases effects of phentermine by pharmacodynamic synergism. Avoid or Use Alternate Drug. Additive pressor effect.

• doxepin

  Monitor Closely (2)doxepin increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  doxepin and topiramate both increase sedation. Modify Therapy/Monitor Closely.Serious - Use Alternative (1)doxepin, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• doxylamine

  Monitor Closely (1)doxylamine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• dronedarone

  Serious - Use Alternative (1)topiramate will decrease the level or effect of dronedarone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• droperidol

  Monitor Closely (2)droperidol and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  droperidol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• droxidopa

  Monitor Closely (1)phentermine and droxidopa both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. May increase risk for supine hypertension

• duloxetine

  Serious - Use Alternative (1)duloxetine, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.

• dutasteride

  Minor (1)topiramate will decrease the level or effect of dutasteride by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• efavirenz

  Minor (1)topiramate will decrease the level or effect of efavirenz by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• eletriptan

  Monitor Closely (1)topiramate will decrease the level or effect of eletriptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• ephedrine

  Monitor Closely (4)ephedrine, phentermine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor.
  
  topiramate increases and ephedrine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  ephedrine and phentermine both decrease sedation. Use Caution/Monitor.
  
  ephedrine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• epinephrine

  Monitor Closely (3)epinephrine and phentermine both decrease sedation. Use Caution/Monitor.
  
  epinephrine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and epinephrine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• epinephrine inhaled

  Monitor Closely (1)phentermine, epinephrine inhaled. Either increases effects of the other by sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• epinephrine racemic

  Monitor Closely (3)epinephrine racemic and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and epinephrine racemic decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  epinephrine racemic and phentermine both decrease sedation. Use Caution/Monitor.

• eplerenone

  Minor (1)topiramate will decrease the level or effect of eplerenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• ergoloid mesylates

  Serious - Use Alternative (1)ergoloid mesylates, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.

• ergotamine

  Serious - Use Alternative (2)topiramate will decrease the level or effect of ergotamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
  
  ergotamine, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.

• erlotinib

  Monitor Closely (1)topiramate will decrease the level or effect of erlotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• erythromycin base

  Serious - Use Alternative (1)topiramate will decrease the level or effect of erythromycin base by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• erythromycin ethylsuccinate

  Serious - Use Alternative (1)topiramate will decrease the level or effect of erythromycin ethylsuccinate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• erythromycin lactobionate

  Serious - Use Alternative (1)topiramate will decrease the level or effect of erythromycin lactobionate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• erythromycin stearate

  Serious - Use Alternative (1)topiramate will decrease the level or effect of erythromycin stearate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• escitalopram

  Serious - Use Alternative (1)escitalopram, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.

• esketamine intranasal

  Monitor Closely (2)esketamine intranasal, topiramate. Either increases toxicity of the other by sedation. Modify Therapy/Monitor Closely.
  
  esketamine intranasal, phentermine. Either increases toxicity of the other by sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. Closely monitor blood pressure with concomitant use of esketamine nasal with stimulants. .

• estazolam

  Monitor Closely (2)estazolam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  estazolam and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• estradiol

  Monitor Closely (1)topiramate will decrease the level or effect of estradiol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• estrogens conjugated synthetic

  Monitor Closely (1)topiramate will decrease the level or effect of estrogens conjugated synthetic by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• estrogens esterified

  Monitor Closely (1)topiramate will decrease the level or effect of estrogens esterified by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Topiramate may compromise the efficacy of estrogens used for contraception or hormone replacement therapies

• estropipate

  Monitor Closely (1)topiramate will decrease the level or effect of estropipate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• ethanol

  Monitor Closely (2)ethanol and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  ethanol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• ether

  Serious - Use Alternative (1)ether increases toxicity of phentermine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.

• ethinylestradiol

  Serious - Use Alternative (1)topiramate will decrease the level or effect of ethinylestradiol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. The efficacy of hormonal contraceptives may be reduced. Use of a nonhormonal contraceptive is recommended.

• ethotoin

  Minor (2)topiramate increases levels of ethotoin by decreasing metabolism. Minor/Significance Unknown.
  
  ethotoin decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown.

• etonogestrel

  Monitor Closely (1)topiramate will decrease the level or effect of etonogestrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• etravirine

  Monitor Closely (1)topiramate will decrease the level or effect of etravirine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• eucalyptus

  Monitor Closely (1)eucalyptus and topiramate both increase sedation. Use Caution/Monitor.Minor (2)eucalyptus increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Minor/Significance Unknown.
  
  topiramate will decrease the level or effect of eucalyptus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• everolimus

  Serious - Use Alternative (1)topiramate will decrease the level or effect of everolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• felodipine

  Monitor Closely (1)topiramate will decrease the level or effect of felodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• fenfluramine

  Monitor Closely (3)fenfluramine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and fenfluramine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  phentermine and fenfluramine both decrease sedation. Use Caution/Monitor.

• fesoterodine

  Monitor Closely (1)topiramate will decrease the level or effect of fesoterodine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• finasteride

  Minor (1)topiramate will decrease the level or effect of finasteride by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• fludrocortisone

  Monitor Closely (1)topiramate will decrease the level or effect of fludrocortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• fluoxetine

  Serious - Use Alternative (1)fluoxetine, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.

• fluphenazine

  Monitor Closely (3)fluphenazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  fluphenazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  fluphenazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• flurazepam

  Monitor Closely (2)flurazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  flurazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• fluvoxamine

  Serious - Use Alternative (1)fluvoxamine and phentermine both increase serotonin levels. Avoid or Use Alternate Drug.

• formoterol

  Monitor Closely (3)formoterol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and formoterol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  formoterol and phentermine both decrease sedation. Use Caution/Monitor.

• fosamprenavir

  Monitor Closely (1)topiramate will decrease the level or effect of fosamprenavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• fosaprepitant

  Monitor Closely (1)topiramate will decrease the level or effect of fosaprepitant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• fosphenytoin

  Monitor Closely (1)fosphenytoin decreases levels of topiramate by increasing metabolism. Use Caution/Monitor.Minor (1)topiramate increases levels of fosphenytoin by decreasing metabolism. Minor/Significance Unknown.

• galantamine

  Minor (1)topiramate will decrease the level or effect of galantamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• ganaxolone

  Monitor Closely (1)topiramate and ganaxolone both increase sedation. Use Caution/Monitor.

• glyburide

  Minor (1)topiramate will decrease the level or effect of glyburide by unknown mechanism. Minor/Significance Unknown. Effect in glycemic control is likely small.

• green tea

  Monitor Closely (1)green tea, phentermine. Other (see comment). Use Caution/Monitor. Comment: Green tea may include caffeine. Caffeine is a CNS-stimulant and additive effects may be seen when coadministered with other CNS stimulants. Caffeine should be avoided or used cautiously.

• guarana

  Minor (1)guarana increases effects of phentermine by pharmacodynamic synergism. Minor/Significance Unknown.

• haloperidol

  Monitor Closely (2)haloperidol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  haloperidol and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• hydralazine

  Monitor Closely (1)hydralazine, phentermine. Mechanism: pharmacodynamic antagonism. Use Caution/Monitor. Sympathomimetics can antagonize the activity of some antihypertensive agents.

• hydrocortisone

  Monitor Closely (1)topiramate will decrease the level or effect of hydrocortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• hydromorphone

  Monitor Closely (2)hydromorphone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  hydromorphone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• hydroxyprogesterone caproate (DSC)

  Monitor Closely (1)topiramate will decrease the level or effect of hydroxyprogesterone caproate (DSC) by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• hydroxyzine

  Monitor Closely (2)hydroxyzine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  hydroxyzine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• iloperidone

  Monitor Closely (3)iloperidone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  topiramate will decrease the level or effect of iloperidone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  iloperidone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• imatinib

  Minor (1)topiramate will decrease the level or effect of imatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• imipramine

  Monitor Closely (2)imipramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  imipramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)topiramate will decrease the level or effect of imipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.Serious - Use Alternative (1)imipramine, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• incobotulinumtoxinA

  Minor (1)topiramate decreases effects of incobotulinumtoxinA by pharmacodynamic antagonism. Minor/Significance Unknown.

• indinavir

  Monitor Closely (1)topiramate will decrease the level or effect of indinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• iobenguane I 123

  Contraindicated (1)phentermine decreases effects of iobenguane I 123 by receptor binding competition. Contraindicated. If clinically appropriate, discontinue drugs that compete for NE receptor sites for at least 5 half-lives; may cause false-negative imaging results.

• iobenguane I 131

  Serious - Use Alternative (1)phentermine will decrease the level or effect of iobenguane I 131 by Other (see comment). Avoid or Use Alternate Drug. Based on the mechanism of action of iobenguane, drugs that reduce catecholamine uptake or that deplete catecholamine stores may interfere with iobenguane uptake into cells, and thus, reduce iobenguane efficacy. Discontinue interfering drugs for at least 5 half-lives before administration of either the dosimetry or an iobenguane dose. Do not administer these drugs until at least 7 days after each iobenguane dose.

• ioflupane I 123

  Monitor Closely (1)phentermine decreases effects of ioflupane I 123 by receptor binding competition. Use Caution/Monitor. Drugs that bind to dopamine transporter receptor with high affinity may interfere with the image following ioflupane I 123 administration.

• isavuconazonium sulfate

  Monitor Closely (1)topiramate will decrease the level or effect of isavuconazonium sulfate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• isocarboxazid

  Contraindicated (1)isocarboxazid increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

• isoflurane

  Serious - Use Alternative (1)isoflurane increases toxicity of phentermine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.

• isoproterenol

  Monitor Closely (3)isoproterenol and phentermine both decrease sedation. Use Caution/Monitor.
  
  topiramate increases and isoproterenol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  isoproterenol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• isradipine

  Minor (1)topiramate will decrease the level or effect of isradipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• itraconazole

  Minor (1)topiramate will decrease the level or effect of itraconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• ketamine

  Monitor Closely (1)ketamine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• ketoconazole

  Minor (1)topiramate will decrease the level or effect of ketoconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• ketotifen, ophthalmic

  Monitor Closely (2)ketotifen, ophthalmic and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  ketotifen, ophthalmic increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• lacosamide

  Monitor Closely (1)topiramate increases toxicity of lacosamide by Other (see comment). Use Caution/Monitor. Comment: Coadministration of lacosamide with sodium channel-blocking antiseizure drugs may increase the risk for AV block, bradycardia, or ventricular tachyarrhythmias. Monitor ECG before beginning lacosamide and after lacosamide is titrated to steady-state.

• lapatinib

  Monitor Closely (1)topiramate will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• lasmiditan

  Monitor Closely (1)lasmiditan, topiramate. Either increases effects of the other by sedation. Use Caution/Monitor. Coadministration of lasmiditan and other CNS depressant drugs, including alcohol have not been evaluated in clinical studies. Lasmiditan may cause sedation, as well as other cognitive and/or neuropsychiatric adverse reactions.

• lemborexant

  Monitor Closely (1)lemborexant will increase the level or effect of topiramate by sedation. Modify Therapy/Monitor Closely. Dosage adjustment may be necessary if lemborexant is coadministered with other CNS depressants because of potentially additive effects.

• levalbuterol

  Monitor Closely (3)topiramate increases and levalbuterol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  levalbuterol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  levalbuterol and phentermine both decrease sedation. Use Caution/Monitor.

• levocarnitine

  Minor (1)topiramate decreases levels of levocarnitine by unspecified interaction mechanism. Minor/Significance Unknown.

• levoketoconazole

  Minor (1)topiramate will decrease the level or effect of levoketoconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• levomilnacipran

  Serious - Use Alternative (1)levomilnacipran and phentermine both increase serotonin levels. Avoid or Use Alternate Drug.

• levonorgestrel intrauterine

  Monitor Closely (1)topiramate decreases levels of levonorgestrel intrauterine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• levonorgestrel oral

  Monitor Closely (1)topiramate decreases levels of levonorgestrel oral by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• levonorgestrel oral/ethinylestradiol/ferrous bisglycinate

  Monitor Closely (1)topiramate will decrease the level or effect of levonorgestrel oral/ethinylestradiol/ferrous bisglycinate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. The efficacy of hormonal contraceptives may be reduced. Use an alternative method of contraception or a backup method when enzyme inducers are used with combined hormonal contraceptives (CHCs), and continue backup contraception for 28 days after discontinuing enzyme inducer to ensure contraceptive reliability.

• levorphanol

  Monitor Closely (2)levorphanol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  levorphanol and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• linagliptin

  Monitor Closely (1)topiramate will increase the level or effect of linagliptin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Use of alternative treatments is strongly recommended when linagliptin is to be administered with a CYP3A4 inducer

• linezolid

  Contraindicated (1)linezolid increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

• lisdexamfetamine

  Monitor Closely (3)lisdexamfetamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  lisdexamfetamine and phentermine both decrease sedation. Use Caution/Monitor.
  
  topiramate increases and lisdexamfetamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• lithium

  Monitor Closely (1)topiramate increases levels of lithium by unspecified interaction mechanism. Use Caution/Monitor. Increase in lithium exposure may occur with doses of up to 600 mg/day; monitor lithium levels when coadministered with high-dose topiramate .

• lofepramine

  Monitor Closely (2)lofepramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  lofepramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Serious - Use Alternative (1)lofepramine, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• lofexidine

  Monitor Closely (2)lofexidine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  lofexidine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• lopinavir

  Monitor Closely (1)topiramate will decrease the level or effect of lopinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• loprazolam

  Monitor Closely (2)loprazolam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  loprazolam and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• loratadine

  Monitor Closely (1)topiramate will decrease the level or effect of loratadine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• lorazepam

  Monitor Closely (2)lorazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  lorazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• lormetazepam

  Monitor Closely (2)lormetazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  lormetazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• lovastatin

  Serious - Use Alternative (1)topiramate will decrease the level or effect of lovastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• loxapine

  Monitor Closely (2)loxapine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  loxapine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• loxapine inhaled

  Monitor Closely (2)loxapine inhaled and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  loxapine inhaled increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• lumefantrine

  Monitor Closely (1)topiramate will decrease the level or effect of lumefantrine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• lurasidone

  Monitor Closely (1)lurasidone, topiramate. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: Potential for increased CNS depressant effects when used concurrently; monitor for increased adverse effects and toxicity.

• maprotiline

  Monitor Closely (2)maprotiline and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  maprotiline increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Serious - Use Alternative (1)maprotiline, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• maraviroc

  Monitor Closely (1)topiramate will decrease the level or effect of maraviroc by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• marijuana

  Monitor Closely (2)marijuana and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  marijuana increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• mavacamten

  Monitor Closely (1)topiramate will increase the level or effect of mavacamten by affecting hepatic enzyme CYP2C19 metabolism. Modify Therapy/Monitor Closely. Inititiation of weak CYP2C19 inhibitors may require decreased mavacamten dose.

• melatonin

  Monitor Closely (2)melatonin and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  melatonin increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• meperidine

  Monitor Closely (2)meperidine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  meperidine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• meprobamate

  Monitor Closely (2)meprobamate increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  meprobamate and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• mestranol

  Monitor Closely (1)topiramate will decrease the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• metaproterenol

  Monitor Closely (3)topiramate increases and metaproterenol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  metaproterenol and phentermine both decrease sedation. Use Caution/Monitor.
  
  metaproterenol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• metaxalone

  Monitor Closely (1)metaxalone and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• metformin

  Monitor Closely (2)phentermine decreases effects of metformin by pharmacodynamic antagonism. Use Caution/Monitor. Patient should be closely observed for loss of blood glucose control; when drugs are withdrawn from a patient receiving metformin, patient should be observed closely for hypoglycemia.
  
  topiramate increases toxicity of metformin by Other (see comment). Use Caution/Monitor. Comment: Decreases serum bicarbonate and induce non-anion gap, hyperchloremic metabolic acidosis.

• methadone

  Monitor Closely (3)topiramate will decrease the level or effect of methadone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  methadone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  methadone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• methamphetamine

  Monitor Closely (3)methamphetamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  methamphetamine and phentermine both decrease sedation. Use Caution/Monitor.

• methazolamide

  Monitor Closely (1)topiramate, methazolamide. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of kidney stone formation.

• methocarbamol

  Monitor Closely (1)methocarbamol and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• methoxyflurane

  Serious - Use Alternative (1)methoxyflurane increases toxicity of phentermine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.

• methyldopa

  Monitor Closely (1)methyldopa increases effects of phentermine by unknown mechanism. Use Caution/Monitor.

• methylenedioxymethamphetamine

  Monitor Closely (3)methylenedioxymethamphetamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and methylenedioxymethamphetamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  methylenedioxymethamphetamine and phentermine both decrease sedation. Use Caution/Monitor.

• methylergonovine

  Serious - Use Alternative (1)methylergonovine, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.

• methylphenidate

  Contraindicated (1)phentermine increases effects of methylphenidate by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

• methylphenidate transdermal

  Monitor Closely (1)methylphenidate transdermal will increase the level or effect of topiramate by decreasing metabolism. Modify Therapy/Monitor Closely. Consider decreasing the dose of these drugs when given coadministered with methylphenidate. Monitor for drug toxiticities when initiating or discontinuing methylphenidate.

• methylprednisolone

  Monitor Closely (1)topiramate will decrease the level or effect of methylprednisolone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• metoclopramide intranasal

  Serious - Use Alternative (1)topiramate, metoclopramide intranasal. Either increases effects of the other by Other (see comment). Avoid or Use Alternate Drug. Comment: Avoid use of metoclopramide intranasal or interacting drug, depending on importance of drug to patient.

• midazolam

  Monitor Closely (3)midazolam and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  midazolam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  topiramate will decrease the level or effect of midazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• midazolam intranasal

  Monitor Closely (1)midazolam intranasal, topiramate. Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Concomitant use of barbiturates, alcohol, or other CNS depressants may increase the risk of hypoventilation, airway obstruction, desaturation, or apnea and may contribute to profound and/or prolonged drug effect.

• midodrine

  Monitor Closely (3)topiramate increases and midodrine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  phentermine and midodrine both decrease sedation. Use Caution/Monitor.
  
  midodrine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• milnacipran

  Serious - Use Alternative (1)milnacipran, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.

• mirtazapine

  Monitor Closely (2)mirtazapine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  mirtazapine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• modafinil

  Monitor Closely (2)modafinil and phentermine both decrease sedation. Use Caution/Monitor.
  
  topiramate increases and modafinil decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• montelukast

  Minor (1)topiramate will decrease the level or effect of montelukast by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• morphine

  Monitor Closely (2)morphine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  morphine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• motherwort

  Monitor Closely (2)motherwort and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  motherwort increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• moxonidine

  Monitor Closely (2)moxonidine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  moxonidine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• nabilone

  Monitor Closely (2)nabilone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  nabilone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• nalbuphine

  Monitor Closely (2)nalbuphine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  nalbuphine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• nefazodone

  Serious - Use Alternative (1)nefazodone, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.

• nelfinavir

  Monitor Closely (1)topiramate will decrease the level or effect of nelfinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• nicardipine

  Monitor Closely (1)topiramate will decrease the level or effect of nicardipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• nifedipine

  Minor (1)topiramate will decrease the level or effect of nifedipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• nilotinib

  Monitor Closely (1)topiramate will decrease the level or effect of nilotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• nimodipine

  Minor (1)topiramate will decrease the level or effect of nimodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• nisoldipine

  Monitor Closely (1)topiramate will decrease the level or effect of nisoldipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• nitrendipine

  Minor (1)topiramate will decrease the level or effect of nitrendipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• norepinephrine

  Monitor Closely (3)norepinephrine and phentermine both decrease sedation. Use Caution/Monitor.
  
  norepinephrine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and norepinephrine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• norethindrone

  Serious - Use Alternative (1)topiramate will decrease the level or effect of norethindrone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration unless benefit outweighs risk. When coadministered, hormonal contraceptives are not a reliable method of effective birth control. Concomitant use may increase incidence of menstruation associated adverse effects (amenorrhea, dysmenorrhea, menorrhagia).

• norethindrone acetate

  Serious - Use Alternative (1)topiramate will decrease the level or effect of norethindrone acetate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration unless benefit outweighs risk. When coadministered, hormonal contraceptives are not a reliable method of effective birth control. Concomitant use may increase incidence of menstruation associated adverse effects (amenorrhea, dysmenorrhea, menorrhagia).

• norethindrone transdermal

  Serious - Use Alternative (1)topiramate will decrease the level or effect of norethindrone transdermal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration unless benefit outweighs risk. When coadministered, hormonal contraceptives are not a reliable method of effective birth control. Concomitant use may increase incidence of menstruation associated adverse effects (amenorrhea, dysmenorrhea, menorrhagia).

• nortriptyline

  Monitor Closely (2)nortriptyline and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  nortriptyline increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Serious - Use Alternative (1)nortriptyline, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• olanzapine

  Monitor Closely (2)olanzapine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  olanzapine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• olopatadine intranasal

  Serious - Use Alternative (1)topiramate and olopatadine intranasal both increase sedation. Avoid or Use Alternate Drug. Coadministration increases risk of CNS depression, which can lead to additive impairment of psychomotor performance and cause daytime impairment.

• onabotulinumtoxinA

  Minor (1)topiramate decreases effects of onabotulinumtoxinA by pharmacodynamic antagonism. Minor/Significance Unknown.

• ondansetron

  Minor (1)topiramate will decrease the level or effect of ondansetron by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• opium tincture

  Monitor Closely (2)opium tincture and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  opium tincture increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• orlistat

  Monitor Closely (1)orlistat decreases levels of topiramate by inhibition of GI absorption. Applies only to oral form of both agents. Modify Therapy/Monitor Closely. Risk of convulsions.

• orphenadrine

  Monitor Closely (1)orphenadrine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• oxazepam

  Monitor Closely (2)oxazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  oxazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• oxybutynin

  Minor (1)topiramate will decrease the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• oxycodone

  Monitor Closely (2)oxycodone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  oxycodone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• oxymorphone

  Monitor Closely (2)oxymorphone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  oxymorphone and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• oxytocin

  Monitor Closely (1)oxytocin increases effects of phentermine by pharmacodynamic synergism. Use Caution/Monitor.

• ozanimod

  Serious - Use Alternative (1)ozanimod increases toxicity of phentermine by sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Avoid or Use Alternate Drug. Because the active metabolite of ozanimod inhibits MAO-B in vitro, there is a potential for serious adverse reactions, including hypertensive crisis. Therefore, coadministration of ozanimod with drugs that can increase norepinephrine or serotonin is not recommended. Monitor for hypertension with concomitant use.

• paclitaxel

  Minor (1)topiramate will decrease the level or effect of paclitaxel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• paclitaxel protein bound

  Minor (1)topiramate will decrease the level or effect of paclitaxel protein bound by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• pacritinib

  Serious - Use Alternative (1)topiramate will decrease the level or effect of pacritinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• paliperidone

  Monitor Closely (2)paliperidone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  paliperidone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• pancuronium

  Minor (1)topiramate decreases effects of pancuronium by pharmacodynamic antagonism. Minor/Significance Unknown.

• papaveretum

  Monitor Closely (2)papaveretum and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  papaveretum increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• papaverine

  Monitor Closely (1)papaverine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• parecoxib

  Minor (1)topiramate will decrease the level or effect of parecoxib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• paroxetine

  Serious - Use Alternative (1)paroxetine, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.

• pazopanib

  Monitor Closely (1)topiramate will decrease the level or effect of pazopanib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• pentazocine

  Monitor Closely (2)pentazocine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  pentazocine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• pentobarbital

  Monitor Closely (2)pentobarbital and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  pentobarbital increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)pentobarbital decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown.

• perampanel

  Serious - Use Alternative (1)topiramate will decrease the level or effect of perampanel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Increased perampanel dose may be needed when coadministered

• perphenazine

  Monitor Closely (3)perphenazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  perphenazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  perphenazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• phendimetrazine

  Monitor Closely (3)topiramate increases and phendimetrazine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  phendimetrazine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  phentermine and phendimetrazine both decrease sedation. Use Caution/Monitor.

• phenelzine

  Contraindicated (1)phenelzine increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

• phenobarbital

  Monitor Closely (2)phenobarbital and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  phenobarbital increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)phenobarbital decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown.

• phentermine

  Monitor Closely (1)topiramate increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• phenylephrine

  Monitor Closely (3)topiramate increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  phentermine and phenylephrine both decrease sedation. Use Caution/Monitor.
  
  phentermine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• phenylephrine PO

  Monitor Closely (3)topiramate increases and phenylephrine PO decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely. .
  
  phentermine and phenylephrine PO both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  phentermine and phenylephrine PO both decrease sedation. Use Caution/Monitor.

• phenytoin

  Monitor Closely (1)phenytoin decreases levels of topiramate by increasing metabolism. Use Caution/Monitor.Minor (1)topiramate increases levels of phenytoin by decreasing metabolism. Minor/Significance Unknown.

• pholcodine

  Monitor Closely (2)pholcodine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  pholcodine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• pimozide

  Monitor Closely (2)pimozide and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  pimozide increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)topiramate will decrease the level or effect of pimozide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• pioglitazone

  Minor (1)topiramate will decrease the level or effect of pioglitazone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• pirbuterol

  Monitor Closely (3)pirbuterol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  pirbuterol and phentermine both decrease sedation. Use Caution/Monitor.
  
  topiramate increases and pirbuterol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• prednisone

  Monitor Closely (1)topiramate will decrease the level or effect of prednisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• primidone

  Monitor Closely (2)primidone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  primidone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Minor (1)primidone decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown.

• procarbazine

  Contraindicated (1)procarbazine increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

• prochlorperazine

  Monitor Closely (3)prochlorperazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  prochlorperazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  prochlorperazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• promazine

  Monitor Closely (1)promazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• promethazine

  Monitor Closely (3)promethazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  promethazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  promethazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.

• propafenone

  Minor (1)topiramate will decrease the level or effect of propafenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• propofol

  Monitor Closely (1)propofol and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• propylhexedrine

  Monitor Closely (3)phentermine and propylhexedrine both decrease sedation. Use Caution/Monitor.
  
  phentermine and propylhexedrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and propylhexedrine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• protriptyline

  Monitor Closely (2)protriptyline and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  protriptyline increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Serious - Use Alternative (1)protriptyline, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• pseudoephedrine

  Monitor Closely (1)phentermine and pseudoephedrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• quazepam

  Monitor Closely (2)quazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  quazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• quetiapine

  Monitor Closely (3)quetiapine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  topiramate will decrease the level or effect of quetiapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  quetiapine and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• quinidine

  Monitor Closely (1)topiramate will decrease the level or effect of quinidine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• quinine

  Minor (1)topiramate will decrease the level or effect of quinine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• ramelteon

  Monitor Closely (1)ramelteon and topiramate both increase sedation. Modify Therapy/Monitor Closely.Minor (1)topiramate will decrease the level or effect of ramelteon by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• ranolazine

  Serious - Use Alternative (1)topiramate will decrease the level or effect of ranolazine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• rapacuronium

  Minor (1)topiramate decreases effects of rapacuronium by pharmacodynamic antagonism. Minor/Significance Unknown.

• rasagiline

  Serious - Use Alternative (1)rasagiline increases effects of phentermine by pharmacodynamic synergism. Avoid or Use Alternate Drug. Phentermine should not be administered during or within 14 days following the use of most MAOIs or drugs with MAO-inhibiting activity. Risk of acute hypertensive episode. .

• repaglinide

  Monitor Closely (1)topiramate will decrease the level or effect of repaglinide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• risperidone

  Monitor Closely (2)risperidone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  risperidone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• ritonavir

  Monitor Closely (1)topiramate will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• rocuronium

  Minor (1)topiramate decreases effects of rocuronium by pharmacodynamic antagonism. Minor/Significance Unknown.

• romidepsin

  Monitor Closely (1)topiramate will decrease the level or effect of romidepsin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• sage

  Monitor Closely (1)sage and topiramate both increase sedation. Use Caution/Monitor.Minor (2)sage decreases effects of topiramate by pharmacodynamic antagonism. Minor/Significance Unknown. Theoretical interaction; some species of sage may cause convulsions.
  
  sage increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Minor/Significance Unknown.

• salmeterol

  Monitor Closely (3)salmeterol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and salmeterol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  salmeterol and phentermine both decrease sedation. Use Caution/Monitor.

• saquinavir

  Monitor Closely (1)topiramate will decrease the level or effect of saquinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• saxagliptin

  Minor (1)topiramate will decrease the level or effect of saxagliptin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• scullcap

  Monitor Closely (2)scullcap and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  scullcap increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• secobarbital

  Monitor Closely (2)secobarbital increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  secobarbital and topiramate both increase sedation. Modify Therapy/Monitor Closely.Minor (1)secobarbital decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown.

• selegiline

  Serious - Use Alternative (1)selegiline increases effects of phentermine by pharmacodynamic synergism. Avoid or Use Alternate Drug. Phentermine should not be administered during or within 14 days following the use of most MAOIs or drugs with MAO-inhibiting activity. Risk of acute hypertensive episode. .

• selegiline transdermal

  Contraindicated (1)selegiline transdermal increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

• serdexmethylphenidate/dexmethylphenidate

  Monitor Closely (2)serdexmethylphenidate/dexmethylphenidate and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  serdexmethylphenidate/dexmethylphenidate and phentermine both decrease sedation. Use Caution/Monitor.Minor (1)serdexmethylphenidate/dexmethylphenidate increases effects of topiramate by decreasing metabolism. Minor/Significance Unknown.

• sertraline

  Serious - Use Alternative (1)sertraline, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.

• sevelamer

  Monitor Closely (1)sevelamer decreases levels of topiramate by increasing elimination. Use Caution/Monitor.

• sevoflurane

  Monitor Closely (1)sevoflurane and topiramate both increase sedation. Modify Therapy/Monitor Closely.Serious - Use Alternative (1)sevoflurane increases toxicity of phentermine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.

• shepherd's purse

  Monitor Closely (2)shepherd's purse and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  shepherd's purse increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• silodosin

  Serious - Use Alternative (1)topiramate will decrease the level or effect of silodosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• simvastatin

  Serious - Use Alternative (1)topiramate will decrease the level or effect of simvastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• sirolimus

  Serious - Use Alternative (1)topiramate will decrease the level or effect of sirolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• sodium oxybate

  Serious - Use Alternative (1)sodium oxybate, topiramate. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.

• solifenacin

  Monitor Closely (1)topiramate will decrease the level or effect of solifenacin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• solriamfetol

  Monitor Closely (1)phentermine and solriamfetol both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.

• stiripentol

  Monitor Closely (1)stiripentol, topiramate. Either increases effects of the other by sedation. Use Caution/Monitor. Concomitant use stiripentol with other CNS depressants, including alcohol, may increase the risk of sedation and somnolence.

• succinylcholine

  Minor (1)topiramate decreases effects of succinylcholine by pharmacodynamic antagonism. Minor/Significance Unknown.

• sufentanil

  Monitor Closely (2)sufentanil increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  sufentanil and topiramate both increase sedation. Modify Therapy/Monitor Closely.Minor (1)topiramate will decrease the level or effect of sufentanil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• sunitinib

  Monitor Closely (1)topiramate will decrease the level or effect of sunitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tacrolimus

  Monitor Closely (1)topiramate will decrease the level or effect of tacrolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tadalafil

  Monitor Closely (1)topiramate will decrease the level or effect of tadalafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tapentadol

  Monitor Closely (2)tapentadol and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  tapentadol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• tazemetostat

  Monitor Closely (1)topiramate will decrease the level or effect of tazemetostat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• temazepam

  Monitor Closely (2)temazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  temazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely.

• temsirolimus

  Monitor Closely (1)topiramate will decrease the level or effect of temsirolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• terbutaline

  Monitor Closely (3)terbutaline and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  terbutaline and phentermine both decrease sedation. Use Caution/Monitor.
  
  topiramate increases and terbutaline decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• theophylline

  Monitor Closely (1)topiramate will decrease the level or effect of theophylline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• thioridazine

  Monitor Closely (3)thioridazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  thioridazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  thioridazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• thiothixene

  Monitor Closely (2)thiothixene and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  thiothixene increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• tipranavir

  Monitor Closely (1)topiramate will decrease the level or effect of tipranavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tobramycin inhaled

  Monitor Closely (1)tobramycin inhaled and topiramate both increase nephrotoxicity and/or ototoxicity. Modify Therapy/Monitor Closely. Avoid concurrent or sequential use to decrease risk for ototoxicity

• tolterodine

  Monitor Closely (1)topiramate will decrease the level or effect of tolterodine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• tolvaptan

  Serious - Use Alternative (1)topiramate will decrease the level or effect of tolvaptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• topiramate

  Monitor Closely (1)topiramate increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• tramadol

  Monitor Closely (2)tramadol and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  tramadol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• tranylcypromine

  Contraindicated (1)tranylcypromine increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

• trazodone

  Monitor Closely (3)trazodone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  topiramate will decrease the level or effect of trazodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
  
  trazodone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.Serious - Use Alternative (2)trazodone, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.
  
  trazodone, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• triamcinolone acetonide injectable suspension

  Monitor Closely (1)topiramate will decrease the level or effect of triamcinolone acetonide injectable suspension by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• triazolam

  Monitor Closely (3)triazolam and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  triazolam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  topiramate will decrease the level or effect of triazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• triclofos

  Monitor Closely (2)triclofos and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  triclofos increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• trifluoperazine

  Monitor Closely (3)trifluoperazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  trifluoperazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
  
  trifluoperazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• trimipramine

  Monitor Closely (2)trimipramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  trimipramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.Serious - Use Alternative (1)trimipramine, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.

• triprolidine

  Monitor Closely (2)triprolidine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
  
  triprolidine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

• ubrogepant

  Monitor Closely (1)topiramate will decrease the level or effect of ubrogepant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Dose adjustment is recommended with concomitant use of ubrogepant and moderate and weak CYP3A4 inducers. (see Dosage Modifications)

• ulipristal

  Serious - Use Alternative (1)topiramate will decrease the level or effect of ulipristal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

• valproic acid

  Monitor Closely (1)valproic acid, topiramate. Either increases toxicity of the other by unknown mechanism. Use Caution/Monitor. Risk of hyperammonemia with or without encephalopathy; pts. with inborn errors of metabolism may be at greater risk. S/S: altered LOC, lethargy, vomiting.Minor (1)topiramate decreases levels of valproic acid by increasing metabolism. Minor/Significance Unknown.

• vardenafil

  Monitor Closely (1)topiramate will decrease the level or effect of vardenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• vecuronium

  Minor (1)topiramate decreases effects of vecuronium by pharmacodynamic antagonism. Minor/Significance Unknown.

• venlafaxine

  Serious - Use Alternative (1)venlafaxine, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.

• verapamil

  Monitor Closely (1)topiramate will decrease the level or effect of verapamil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

• vincristine liposomal

  Minor (1)topiramate will decrease the level or effect of vincristine liposomal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• xylometazoline

  Monitor Closely (3)phentermine and xylometazoline both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and xylometazoline decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
  
  phentermine and xylometazoline both decrease sedation. Use Caution/Monitor.

• yerba mate

  Minor (1)yerba mate increases effects of phentermine by pharmacodynamic synergism. Minor/Significance Unknown.

• yohimbe

  Serious - Use Alternative (1)yohimbe, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

• yohimbine

  Monitor Closely (3)phentermine and yohimbine both decrease sedation. Use Caution/Monitor.
  
  phentermine and yohimbine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
  
  topiramate increases and yohimbine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.

• zaleplon

  Minor (1)topiramate will decrease the level or effect of zaleplon by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• ziconotide

  Monitor Closely (2)ziconotide increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  topiramate and ziconotide both increase sedation. Modify Therapy/Monitor Closely.

• ziprasidone

  Monitor Closely (2)ziprasidone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
  
  ziprasidone and topiramate both increase sedation. Modify Therapy/Monitor Closely.Minor (1)topiramate will decrease the level or effect of ziprasidone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• zolpidem

  Minor (1)topiramate will decrease the level or effect of zolpidem by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

• zonisamide

  Minor (1)topiramate will decrease the level or effect of zonisamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.