phentermine/topiramate (Rx)

Brand and Other Names:Qsymia

Dosing & Uses

AdultPediatric

Dosing Forms & Strengths

Phentermine (immediate-release)/topiramate (extended-release)

capsule: Schedule IV

  • 3.75mg/23mg
  • 7.5mg/46mg
  • 11.25mg/69mg
  • 15mg/92mg

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

Dosing Forms & Strengths

Phentermine (immediate-release)/topiramate (extended-release)

capsule: Schedule IV

  • 3.75mg/23mg
  • 7.5mg/46mg
  • 11.25mg/69mg
  • 15mg/92mg

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

Next:

Interactions

Interaction Checker

and phentermine/topiramate

No Results

     activity indicator 
    No Interactions Found
    Interactions Found

    Contraindicated

      Serious - Use Alternative

        Significant - Monitor Closely

          Minor

            All Interactions Sort By:
             activity indicator 

            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 (343)

            • 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.

            • buprenorphine, long-acting injection

              buprenorphine, long-acting injection 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.

            • fentanyl

              fentanyl and topiramate both increase sedation. 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.

            • fentanyl intranasal

              fentanyl intranasal and topiramate both increase sedation. Use Caution/Monitor.

            • fentanyl iontophoretic transdermal system

              fentanyl iontophoretic transdermal system and topiramate both increase sedation. Use Caution/Monitor.

            • fentanyl transdermal

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

            • fesoterodine

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

            • 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.

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            Adverse Effects

            >10%

            Paresthesia (4.2-19.9%)

            Dry mouth (6.7-19.1%)

            Constipation (7.9-16.1%)

            URI (12.2-15.8%)

            Metabolic acidosis (6.4-12.8%)

            Nasopharyngitis (9.4-12.5%)

            Headache (7-10.6%)

            1-10%

            Insomnia (5-9.4%)

            Dysgeusia (1.3-9.4%)

            Dizziness (2.9-8.6%)

            Increased serum creatinine (2.1-8.4%)

            Sinusitis (6.8-7.8%)

            Nausea (3.6-7.2%)

            Bronchitis (4.4-6.7%)

            Back pain (5.4-6.6%)

            Diarrhea (5-6.4%)

            Blurred vision (4-6.3%)

            Fatigue (4.4-5.9%)

            UTI (3.3-5.2%)

            Hypokalemia (persistent) (0.4-4.9%)

            Cough (3.3-4.8%)

            Depression (2.8-4.3%)

            Anxiety (1.8-4.1%)

            Irritability (1.7-3.7%)

            Alopecia (1.7-3.7%)

            Hypoesthesia (0.8-3.7%)

            Disturbance in attention (0.4-3.5%)

            GERD (0.8-3.2%)

            Extremity pain (2.1-3%)

            Musculoskeletal pain (0.8-3%)

            Muscle spasms (2.8-2.9%)

            Dyspepsia (2.1-2.8%)

            Sinus congestion (2-2.6%)

            Rash (1.7-2.6%)

            Pharyngeal pain (1.2-2.5%)

            Dry eye (0.8-2.5%)

            Gastroenteritis (0.8-2.5%)

            Hypokalemia (acute) (0.4-2.5%)

            Palpitations (0.8-2.4%)

            Eye pain (2.1-2.2%)

            Neck pain (1.2-2.2%)

            Oral paresthesia (0.2-2.2%)

            Decreased appetite (1.5-2.1%)

            Nephrolithiasis (0.2-1.2%)

            Dysmenorrhea (0.4-2.1%)

            Chest discomfort (0.2-2.1%)

            Thirst (1.8-2%)

            Nasal congestion (1.2-2%)

            Postmarketing Reports

            Phentermine

            • Allergic: Urticaria
            • Cardiovascular: Increased blood pressure, ischemic events
            • CNS: Euphoria, psychosis, tremor
            • Reproductive: Changes in libido, impotence

            Topiramate

            • Central nervous system: Suicidal behavior and ideation
            • Dermatologic: Bullous skin reactions (eg, erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis), pemphigus
            • Gastrointestinal: Pancreatitis
            • Hepatic: Hepatic failure (including fatalities), hepatitis
            • Metabolic: Hyperammonemia, hypothermia
            • Ophthalmic: Maculopathy, angle closure glaucoma, increased intraocular pressure
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            Warnings

            Contraindications

            Hypersensitivity or idiosyncrasy to topiramate or sympathomimetic amines

            Pregnancy

            Glaucoma

            Hyperthyroidism

            Taking or within 14 days of stopping MAOIs (risk hypertensive crisis)

            Cautions

            May cause fetal harm

            May increase resting heart rate (HR) up to 20 bpm; reduce dose or discontinue use with sustained increase in resting HR; caution in patients with history of cardiac or cerebrovascular disease

            Antiepileptic drugs (AEDs), including topiramate, increase the risk of suicidal thoughts or behavior; discontinue if suicidal thoughts or behaviors emerge; avoid in patients with history of suicidal attempts or active suicidal ideation

            Can cause mood disorders, including depression, anxiety, and insomnia

            Cognitive dysfunction (eg, concentration/attention impairment, difficulty with memory, and speech or language problems, particularly word-finding difficulties); rapid titration or high initial doses associated with higher rates cognitive difficulties

            Associated with reduction in height velocity (centimeters of height gained per year) in obese pediatric patients 12-17 years of age; monitor height velocity in pediatric patients receiving therapy; consider dosage reduction or discontinuation of therapy if pediatric patients are not growing or gaining height as expected

            Phentermine/topiramate associated with increased serum creatinine that reflects a decreased renal function

            Adjust antidiabetic drugs according to patient’s blood glucose as patient loses weight

            As patient loses weight, adjust antihypertensive medications to avoid risk of hypotension

            Avoid abrupt withdrawal of topiramate (particularly at higher doses); associated with seizures in patients with history of seizures or epilepsy

            Kidney stone formation reported; topiramate inhibits carbonic anhydrase activity and promotes kidney stone formation by reducing urinary citrate excretion and increasing urine pH; risk may increase further with ketogenic diet; patients on a ketogenic diet may be at increased risk for kidney stone formation; Increased ratio of urinary calcium/citrate increases risk of kidney stones and/or nephrocalcinosis

            Oligohidrosis, infrequently resulting in hospitalization, reported in association with topiramate; caution during physical activity, especially in hot weather; advise all patients and caregivers to monitor for decreased sweating and increased body temperature during physical activity; especially in hot weather; patients on concomitant medications that predispose them to heat-related disorders may be at increased risk

            Serious skin reactions (eg, Stevens-Johnson syndrome [SJS], toxic epidermal necrolysis [TEN]) reported; discontinue at first sign of rash, unless rash is clearly not drug-related; do not reinitiate if SJS or TEN confirmed

            Contains FD&C yellow No. 5 (tartrazine) which may cause allergic reactions in susceptible individuals (eg, asthmatics, aspirin hypersensitivity)

            Can increase risk of hypokalemia through inhibition of carbonic anhydrase activity; when this drug is used in conjunction with non-potassium sparing diuretics may further potentiate potassium-wasting; measure potassium before and during treatment

            Ophthalmic effects

            • Acute myopia associated with secondary angle-closure glaucoma reported with topiramate; symptoms include acute onset of decreased visual acuity and/or ocular pain
            • Syndrome may be associated with supraciliary effusion resulting in anterior displacement of lens and iris, with secondary angle-closure glaucoma
            • Symptoms typically occur within 1 month of initiating treatment with topiramate but may occur at any time during therapy; in contrast to primary narrow-angle glaucoma, which is rare under 40 years of age, secondary angle-closure glaucoma associated with topiramate has been reported in pediatric patients as well as adults; primary treatment to reverse symptoms is discontinuation of therapy as rapidly as possible
            • Ophthalmologic findings can include myopia, mydriasis, anterior chamber shallowing, ocular hyperemia, choroidal detachments, retinal pigment epithelial detachments, macular striae, and increased intraocular pressure
            • Elevated intraocular pressure of any etiology, if left untreated, can lead to serious adverse reactions including permanent loss of vision
            • Visual field defects (independent of elevated intraocular pressure) reported in clinical trials and in postmarketing experience in patients receiving topiramate; in clinical trials, most of these events were reversible after topiramate discontinuation; if visual problems occur at any time during treatment, consider discontinuing therapy

            Metabolic acidosis

            • Hyperchloremic, non-anion gap, metabolic acidosis (decreased serum bicarbonate below the normal reference range without chronic respiratory alkalosis) reported
            • Manifestations of acute or chronic metabolic acidosis may include hyperventilation, nonspecific symptoms such as fatigue and anorexia, or more severe sequelae including cardiac arrhythmias or stupor
            • Chronic, untreated metabolic acidosis may increase risk for nephrolithiasis or nephrocalcinosis and may result in osteomalacia and/or osteoporosis with an increased risk for fractures
            • Chronic metabolic acidosis in pediatric patients may reduce growth rates, which may decrease maximal height achieved
            • Measure electrolytes including serum bicarbonate prior to starting therapy and during treatment; if persistent metabolic acidosis develops while taking therapy, reduce dosage or discontinue treatment

            Risk of hypoglycemia in type 2 diabetes mellitus

            • Weight loss may increase risk of hypoglycemia in patients with type 2 diabetes mellitus treated with insulin and/or insulin secretagogues (eg, sulfonylureas)
            • This drug has not been studied in combination with insulin; measure blood glucose levels prior to starting therapy and during treatment in patients with type 2 diabetes on antidiabetic medication
            • Risk of hypoglycemia may be lowered by a reduction of dosage of insulin and/or insulin secretagogues; if a patient develops hypoglycemia after starting therapy; appropriate changes should be made to antidiabetic drug regimen

            Drug interaction overview

            • MAOIs
              • Contraindicated if taking MAOIs or within 14 days after stopping MAOIs
              • Coadministration of phentermine with MAOIs increases risk of hypertensive crisis
            • Oral contraceptives
              • Irregular bleeding (spotting) may occur; do not discontinue contraception, but notify physician
              • Coadministration of phentermine/topiramate 15 mg/92 mg a single dose of oral contraceptive containing 35 mcg ethinyl estradiol/norethindrone 35 mcg/1 mg in obese otherwise healthy volunteers, decreased systemic exposure of ethinyl estradiol by 16% and increased the exposure of norethindrone by 22%
              • Interaction not anticipated to increase risk of pregnancy, irregular bleeding (spotting) may occur more frequently owing to both increased exposure to the progestin and lower exposure to the estrogen, which tends to stabilize the endometrium
            • CNS depressants/alcohol
              • Can cause cognitive dysfunction (eg, impairment of concentration/ attention, difficulty with memory, and speech or language problems, particularly word-finding difficulties); rapid titration or high initial doses may be associated with higher rates of cognitive events such as attention, memory, and language/word-finding difficulties
              • Increased drowsiness and decreases cognitive function; warn against excessive alcohol intake and avoid driving or doing functions that require mental alertness; consider dose reduction if cognitive dysfunction persists
              • Coadministration with alcohol or central nervous system (CNS) depressant drugs with this drug may potentiate CNS depression or other centrally mediated effects of these agents, such as dizziness, cognitive adverse reactions, drowsiness, light- headedness, impaired coordination, and somnolence
              • Caution patients about operating hazardous machinery, including automobiles, until they are reasonably certain QSYMIA therapy does not affect them adversely; caution patients against excessive alcohol intake while receiving this drug; if cognitive dysfunction persists, consider dosage reduction or discontinuation of therapy
            • Nonpotassium sparing diuretics
              • Measure serum potassium levels before and during treatment
              • Coadministration may potentiate potassium-wasting action of these diuretics
            • Antiepileptics
              • Consider measuring blood ammonia in patients in whom the onset of hypothermia or encephalopathy reported
              • Topiramate levels decreased if coadministered with phenytoin or carbamazepine by 48% and 40% respectively
              • Coadministration of valproic acid and topiramate associated with hyperammonemia with and without encephalopathy; also associated with hypothermia
            • Carbonic anhydrase inhibitors
              • Avoid; if unavoidable, monitor patient for appearance or worsening metabolic acidosis
              • Coadministration of topiramate with any other carbonic anhydrase inhibitor may increase severity of metabolic acidosis and may also increase risk of kidney stone formation
            • Pioglitazone
              • Consider increased glycemic monitoring
              • Coadministration of topiramate with pioglitazone may decreased systemic exposure of pioglitazone (and active metabolites)
            • Amitriptyline
              • Dosage modification of amitriptyline may be necessary
              • Reports of large increase in amitriptyline concentration if coadministered with topiramate; adjust amitriptyline dose according to the patient's clinical response and not on amitriptyline levels
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            Pregnancy & Lactation

            Pregnancy

            Contraindicated in pregnant patients; use can cause fetal harm and weight loss offers no clear clinical benefit to a pregnant patient; available data from pregnancy registries and epidemiologic studies indicate increased risk of major congenital malformations, including but not limited to cleft lip and/or cleft palate (oral clefts), and of being SGA in infants exposed in utero to topiramate

            Maternal obesity increases risk for congenital malformations, including neural tube defects, cardiac malformations, oral clefts, and limb reduction defects; in addition, weight loss during pregnancy may result in fetal harm; appropriate weight gain based on pre-pregnancy weight is currently recommended for all pregnant patients, including those who are already overweight or obese, due to obligatory weight gain that occurs in maternal tissues during pregnancy

            Therapy can cause metabolic acidosis; effect of topiramate-induced metabolic acidosis has not been studied in pregnancy; however, metabolic acidosis in pregnancy (due to other causes) can cause decreased fetal growth, decreased fetal oxygenation, and fetal death, and may affect the fetus’ ability to tolerate labor

            Therapy can cause fetal harm when administered to a pregnant patient; advise patients who can become pregnant to use effective contraception during therapy

            For patients taking combined oral contraceptives (COCs), therapy may cause irregular bleeding; advise patients not to discontinue taking their COC and to contact their healthcare provider

            Animal data

            • When phentermine and topiramate were co-administered to rats at doses of 3.75 and 25 mg/kg, respectively [approximately 2 times maximum recommended human dose (MRHD) based on area under the curve (AUC)], or at the same dose to rabbits (approximately 0.1 times and 1 time, respectively, the clinical exposures at the MRHD based on AUC) there were no drug-related malformations
            • However, structural malformations, including craniofacial defects and reduced fetal weights occurred in offspring of multiple species of pregnant animals administered topiramate at clinically relevant doses; advise pregnant women of potential risk to a fetus

            Lactation

            Drug components are present in human milk; there are no data on effects of topiramate and phentermine on milk production; diarrhea and somnolence reported in breastfed infants with maternal use of topiramate; there are no data on effects of phentermine in breastfed infants

            Because of potential for serious adverse reactions, including changes in sleep, irritability, hypertension, vomiting, tremor and weight loss in breastfed infants with maternal use of phentermine, advise patients that breastfeeding is not recommended during therapy

            Pregnancy Categories

            A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

            B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

            C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

            D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

            X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

            NA: Information not available.

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            Pharmacology

            Mechanism of Action

            Phentermine: Sympathomimetic amine; induces anorectic effect via release of norepinephrine in the hypothalamus causing appetite suppression by increasing blood leptin concentration; exact mechanism of action unknown

            Topiramate: Effect may be through appetite suppression and satiety enhancement that is induced by a combination of pharmacologic effects including augmenting neurotransmitter gamma-aminobutyrate activity, voltage-gated ion channels modulation, AMPA/kainite excitatory glutamate receptor inhibition, or carbonic anhydrase inhibition

            Absorption

            Phentermine (15 mg dose)

            • Peak Plasma Time: 6 hr
            • Peak Plasma Concentration: 49.1 ng/mL
            • AUC: 1990-2000 ng⋅hr/mL

            Topiramate (92 mg dose)

            • Peak Plasma Time: 9 hr
            • Peak Plasma Concentration: 1020 ng/mL
            • AUC: 61,600-68,000 ng⋅hr/mL

            Distribution

            Phentermine

            • Protein Bound: 17.5%
            • Vd: 348 L

            Topiramate

            • Protein Bound: 15-41%
            • Vd: 50.8 L (central compartment); 13.1 L (peripheral compartment)

            Metabolism

            Phentermine

            • Metabolized by 2 metabolic pathways, p-hydroxylation on the aromatic ring and N-oxidation on the aliphatic side chain
            • CYP3A4 primarily metabolizes phentermine but does not show extensive metabolism
            • Monoamine oxidase (MAO)-A and MAO-B do not metabolize phentermine

            Topiramate

            • Not extensively metabolized

            Elimination

            Phentermine

            • Half-life: 20 hr (terminal)
            • Clearance: 8.79 L/hr
            • Excretion: 70-80% urine (as unchanged drug)

            Topiramate

            • Half-life: 65 hr (terminal)
            • Clearance: 1.17 L/hr
            • Excretion: 70% urine (as unchanged drug)
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            Administration

            Oral Administration

            Take once daily in morning with or without food

            Avoid dosing in evening owing to possible insomnia

            Discontinue 15 mg/92 mg gradually by taking every other day for at least 1 week before stopping treatment altogether, due to possibility of precipitating seizures

            Storage

            Store at 20-25ºC (68-77ºF); excursions permitted to 15-30ºC (59-86ºF)

            Keep container tightly closed and protect from moisture

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            Images

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            Patient Handout

            A Patient Handout is not currently available for this monograph.
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            Formulary

            FormularyPatient Discounts

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            Tier Description
            1 This drug is available at the lowest co-pay. Most commonly, these are generic drugs.
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            Medscape prescription drug monographs are based on FDA-approved labeling information, unless otherwise noted, combined with additional data derived from primary medical literature.