Dosing & Uses
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
Interactions
Interaction Checker
No Results

Contraindicated
Serious - Use Alternative
Significant - Monitor Closely
Minor

Contraindicated (8)
- iobenguane I 123
phentermine decreases effects of iobenguane I 123 by receptor binding competition. Contraindicated. If clinically appropriate, discontinue drugs that compete for NE receptor sites for at least 5 half-lives; may cause false-negative imaging results.
- isocarboxazid
isocarboxazid increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.
- linezolid
linezolid increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.
- methylphenidate
phentermine increases effects of methylphenidate by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.
- phenelzine
phenelzine increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.
- procarbazine
procarbazine increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.
- selegiline transdermal
selegiline transdermal increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.
- tranylcypromine
tranylcypromine increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.
Serious - Use Alternative (62)
- amitriptyline
amitriptyline, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.
- amoxapine
amoxapine, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.
- cabergoline
cabergoline, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.
- calcium/magnesium/potassium/sodium oxybates
calcium/magnesium/potassium/sodium oxybates, topiramate. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.
- citalopram
citalopram, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.
- clomipramine
clomipramine, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.
- desflurane
desflurane increases toxicity of phentermine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.
- desipramine
desipramine, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.
- dihydroergotamine
topiramate will decrease the level or effect of dihydroergotamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
dihydroergotamine, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension. - dihydroergotamine intranasal
dihydroergotamine intranasal, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.
topiramate will decrease the level or effect of dihydroergotamine intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. - doxapram
doxapram increases effects of phentermine by pharmacodynamic synergism. Avoid or Use Alternate Drug. Additive pressor effect.
- dronedarone
topiramate will decrease the level or effect of dronedarone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- doxepin
doxepin, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.
- duloxetine
duloxetine, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.
- ergoloid mesylates
ergoloid mesylates, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.
- ergotamine
topiramate will decrease the level or effect of ergotamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
ergotamine, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension. - erythromycin base
topiramate will decrease the level or effect of erythromycin base by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- escitalopram
escitalopram, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.
- erythromycin ethylsuccinate
topiramate will decrease the level or effect of erythromycin ethylsuccinate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- erythromycin lactobionate
topiramate will decrease the level or effect of erythromycin lactobionate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- erythromycin stearate
topiramate will decrease the level or effect of erythromycin stearate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- ether
ether increases toxicity of phentermine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.
- ethinylestradiol
topiramate will decrease the level or effect of ethinylestradiol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. The efficacy of hormonal contraceptives may be reduced. Use of a nonhormonal contraceptive is recommended.
- everolimus
topiramate will decrease the level or effect of everolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- fluoxetine
fluoxetine, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.
- fluvoxamine
fluvoxamine and phentermine both increase serotonin levels. Avoid or Use Alternate Drug.
- imipramine
imipramine, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.
- iobenguane I 131
phentermine will decrease the level or effect of iobenguane I 131 by Other (see comment). Avoid or Use Alternate Drug. Based on the mechanism of action of iobenguane, drugs that reduce catecholamine uptake or that deplete catecholamine stores may interfere with iobenguane uptake into cells, and thus, reduce iobenguane efficacy. Discontinue interfering drugs for at least 5 half-lives before administration of either the dosimetry or an iobenguane dose. Do not administer these drugs until at least 7 days after each iobenguane dose.
- isoflurane
isoflurane increases toxicity of phentermine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.
- levomilnacipran
levomilnacipran and phentermine both increase serotonin levels. Avoid or Use Alternate Drug.
- lofepramine
lofepramine, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.
- lovastatin
topiramate will decrease the level or effect of lovastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- maprotiline
maprotiline, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.
- methoxyflurane
methoxyflurane increases toxicity of phentermine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.
- methylergonovine
methylergonovine, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.
- metoclopramide intranasal
topiramate, metoclopramide intranasal. Either increases effects of the other by Other (see comment). Avoid or Use Alternate Drug. Comment: Avoid use of metoclopramide intranasal or interacting drug, depending on importance of drug to patient.
- milnacipran
milnacipran, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.
- nefazodone
nefazodone, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.
- norethindrone
topiramate will decrease the level or effect of norethindrone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration unless benefit outweighs risk. When coadministered, hormonal contraceptives are not a reliable method of effective birth control. Concomitant use may increase incidence of menstruation associated adverse effects (amenorrhea, dysmenorrhea, menorrhagia).
- norethindrone acetate
topiramate will decrease the level or effect of norethindrone acetate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration unless benefit outweighs risk. When coadministered, hormonal contraceptives are not a reliable method of effective birth control. Concomitant use may increase incidence of menstruation associated adverse effects (amenorrhea, dysmenorrhea, menorrhagia).
- norethindrone transdermal
topiramate will decrease the level or effect of norethindrone transdermal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration unless benefit outweighs risk. When coadministered, hormonal contraceptives are not a reliable method of effective birth control. Concomitant use may increase incidence of menstruation associated adverse effects (amenorrhea, dysmenorrhea, menorrhagia).
- nortriptyline
nortriptyline, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.
- olopatadine intranasal
topiramate and olopatadine intranasal both increase sedation. Avoid or Use Alternate Drug. Coadministration increases risk of CNS depression, which can lead to additive impairment of psychomotor performance and cause daytime impairment.
- ozanimod
ozanimod increases toxicity of phentermine by sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Avoid or Use Alternate Drug. Because the active metabolite of ozanimod inhibits MAO-B in vitro, there is a potential for serious adverse reactions, including hypertensive crisis. Therefore, coadministration of ozanimod with drugs that can increase norepinephrine or serotonin is not recommended. Monitor for hypertension with concomitant use.
- pacritinib
topiramate will decrease the level or effect of pacritinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- paroxetine
paroxetine, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.
- perampanel
topiramate will decrease the level or effect of perampanel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Increased perampanel dose may be needed when coadministered
- protriptyline
protriptyline, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.
- ranolazine
topiramate will decrease the level or effect of ranolazine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- rasagiline
rasagiline increases effects of phentermine by pharmacodynamic synergism. Avoid or Use Alternate Drug. Phentermine should not be administered during or within 14 days following the use of most MAOIs or drugs with MAO-inhibiting activity. Risk of acute hypertensive episode. .
- selegiline
selegiline increases effects of phentermine by pharmacodynamic synergism. Avoid or Use Alternate Drug. Phentermine should not be administered during or within 14 days following the use of most MAOIs or drugs with MAO-inhibiting activity. Risk of acute hypertensive episode. .
- sertraline
sertraline, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.
- sevoflurane
sevoflurane increases toxicity of phentermine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.
- silodosin
topiramate will decrease the level or effect of silodosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- simvastatin
topiramate will decrease the level or effect of simvastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- sirolimus
topiramate will decrease the level or effect of sirolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- sodium oxybate
sodium oxybate, topiramate. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.
- tolvaptan
topiramate will decrease the level or effect of tolvaptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- trazodone
trazodone, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.
trazodone, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome. - trimipramine
trimipramine, phentermine. Other (see comment). Avoid or Use Alternate Drug. Comment: Tricyclic antidepressants increase or decrease effects of sympathomimetics, by blocking reuptake of NE, or blocking uptake of indirect sympathomimetics into the adrenergic neuron.
- ulipristal
topiramate will decrease the level or effect of ulipristal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.
- venlafaxine
venlafaxine, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.
Monitor Closely (338)
- acetazolamide
topiramate, acetazolamide. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of kidney stone formation.
- acrivastine
acrivastine and topiramate both increase sedation. Use Caution/Monitor.
- albuterol
albuterol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
topiramate increases and albuterol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
albuterol and phentermine both decrease sedation. Use Caution/Monitor. - alfentanil
alfentanil and topiramate both increase sedation. Modify Therapy/Monitor Closely.
alfentanil increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - almotriptan
topiramate will decrease the level or effect of almotriptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- alprazolam
alprazolam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- alprazolam
topiramate will decrease the level or effect of alprazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
alprazolam and topiramate both increase sedation. Modify Therapy/Monitor Closely. - amiodarone
topiramate will decrease the level or effect of amiodarone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- amitriptyline
amitriptyline and topiramate both increase sedation. Modify Therapy/Monitor Closely.
amitriptyline increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
topiramate increases toxicity of amitriptyline by unspecified interaction mechanism. Use Caution/Monitor. Amitriptyline levels may increase; adjust dose based on clinical response and not on basis of plasma levels. - amobarbital
amobarbital increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
amobarbital and topiramate both increase sedation. Modify Therapy/Monitor Closely. - amoxapine
amoxapine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
amoxapine and topiramate both increase sedation. Modify Therapy/Monitor Closely. - apomorphine
apomorphine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- arformoterol
arformoterol and phentermine both decrease sedation. Use Caution/Monitor.
arformoterol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. - aprepitant
topiramate will decrease the level or effect of aprepitant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- arformoterol
topiramate increases and arformoterol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
- aripiprazole
aripiprazole increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
topiramate will decrease the level or effect of aripiprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
aripiprazole and topiramate both increase sedation. Modify Therapy/Monitor Closely. - armodafinil
armodafinil and phentermine both decrease sedation. Use Caution/Monitor.
topiramate increases and armodafinil decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely. - artemether/lumefantrine
topiramate will decrease the level or effect of artemether/lumefantrine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- azelastine
azelastine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- asenapine
asenapine and topiramate both increase sedation. Use Caution/Monitor.
- asenapine transdermal
asenapine transdermal and topiramate both increase sedation. Use Caution/Monitor.
- atogepant
topiramate will decrease the level or effect of atogepant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- atorvastatin
topiramate will decrease the level or effect of atorvastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- avanafil
topiramate will decrease the level or effect of avanafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. For patients with ED, monitor response carefully because of potential for decreased effectiveness.
- avapritinib
avapritinib and topiramate both increase sedation. Use Caution/Monitor.
- axitinib
topiramate decreases levels of axitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- azelastine
azelastine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- baclofen
baclofen and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- bazedoxifene/conjugated estrogens
topiramate will decrease the level or effect of bazedoxifene/conjugated estrogens by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- belladonna and opium
belladonna and opium and topiramate both increase sedation. Modify Therapy/Monitor Closely.
belladonna and opium increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - benazepril
phentermine decreases effects of benazepril by pharmacodynamic antagonism. Use Caution/Monitor.
- benperidol
benperidol and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- benperidol
benperidol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- benzhydrocodone/acetaminophen
benzhydrocodone/acetaminophen and topiramate both increase sedation. Use Caution/Monitor.
- benzphetamine
benzphetamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
topiramate increases and benzphetamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
phentermine and benzphetamine both decrease sedation. Use Caution/Monitor. - brexanolone
brexanolone, topiramate. Either increases toxicity of the other by sedation. Use Caution/Monitor.
- bromocriptine
bromocriptine, phentermine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Hypertension, V tach.
- brexpiprazole
brexpiprazole and topiramate both increase sedation. Use Caution/Monitor.
- brimonidine
brimonidine and topiramate both increase sedation. Use Caution/Monitor.
- brinzolamide
topiramate, brinzolamide. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of kidney stone formation.
- brivaracetam
brivaracetam and topiramate both increase sedation. Use Caution/Monitor.
- brompheniramine
brompheniramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
brompheniramine and topiramate both increase sedation. Modify Therapy/Monitor Closely. - budesonide
topiramate will decrease the level or effect of budesonide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- buprenorphine buccal
buprenorphine buccal increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- buprenorphine
buprenorphine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- buprenorphine buccal
buprenorphine buccal and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- buprenorphine subdermal implant
buprenorphine subdermal implant and topiramate both increase sedation. Use Caution/Monitor.
- buprenorphine transdermal
buprenorphine transdermal and topiramate both increase sedation. Use Caution/Monitor.
- buspirone
topiramate will decrease the level or effect of buspirone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- butabarbital
butabarbital and topiramate both increase sedation. Modify Therapy/Monitor Closely.
butabarbital increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - butalbital
butalbital and topiramate both increase sedation. Modify Therapy/Monitor Closely.
butalbital increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - butorphanol
butorphanol and topiramate both increase sedation. Modify Therapy/Monitor Closely.
butorphanol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - caffeine
topiramate increases and caffeine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
caffeine and phentermine both decrease sedation. Use Caution/Monitor. - captopril
phentermine decreases effects of captopril by pharmacodynamic antagonism. Use Caution/Monitor. Phentermine may decrease the antihypertensive effect of ACE Inhibitors.
- carbamazepine
topiramate will decrease the level or effect of carbamazepine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
carbamazepine decreases levels of topiramate by increasing metabolism. Use Caution/Monitor. - carbinoxamine
carbinoxamine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
carbinoxamine and topiramate both increase sedation. Modify Therapy/Monitor Closely. - carisoprodol
carisoprodol and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- chloral hydrate
chloral hydrate increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- cenobamate
cenobamate, topiramate. Either increases effects of the other by sedation. Use Caution/Monitor.
- chloral hydrate
chloral hydrate and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- chlordiazepoxide
chlordiazepoxide and topiramate both increase sedation. Modify Therapy/Monitor Closely.
chlordiazepoxide increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - chlorpheniramine
chlorpheniramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
chlorpheniramine and topiramate both increase sedation. Modify Therapy/Monitor Closely. - chlorpromazine
chlorpromazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
chlorpromazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
chlorpromazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - chlorzoxazone
chlorzoxazone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- cinnarizine
cinnarizine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- cilostazol
topiramate will decrease the level or effect of cilostazol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- cinacalcet
topiramate will decrease the level or effect of cinacalcet by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- cinnarizine
cinnarizine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- clemastine
clemastine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
clemastine and topiramate both increase sedation. Modify Therapy/Monitor Closely. - clobazam
topiramate, clobazam. Other (see comment). Use Caution/Monitor. Comment: Concomitant administration can increase the potential for CNS effects (e.g., increased sedation or respiratory depression).
- clomipramine
clomipramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- clomipramine
clomipramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- clonazepam
clonazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely.
clonazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - clopidogrel
topiramate will increase the level or effect of clopidogrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. CYP3A4 inducers may increase the metabolism of clopidogrel to its active metabolite. Monitor patients for potential increase in antiplatelet effects when CYP3A4 inducers are used in combination with clopidogrel
- clorazepate
clorazepate increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- clorazepate
clorazepate and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- clozapine
clozapine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
topiramate will decrease the level or effect of clozapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
clozapine and topiramate both increase sedation. Modify Therapy/Monitor Closely. - codeine
codeine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
codeine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - colchicine
topiramate will decrease the level or effect of colchicine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- cyclizine
cyclizine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- conivaptan
topiramate will decrease the level or effect of conivaptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- conjugated estrogens
topiramate will decrease the level or effect of conjugated estrogens by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- conjugated estrogens, vaginal
topiramate will decrease the level or effect of conjugated estrogens, vaginal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- cortisone
topiramate will decrease the level or effect of cortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- cyclizine
cyclizine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- cyclobenzaprine
cyclobenzaprine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- cyclosporine
topiramate will decrease the level or effect of cyclosporine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- cyproheptadine
cyproheptadine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
cyproheptadine and topiramate both increase sedation. Modify Therapy/Monitor Closely. - dantrolene
dantrolene and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- desipramine
desipramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- daridorexant
topiramate and daridorexant both increase sedation. Modify Therapy/Monitor Closely. Coadministration increases risk of CNS depression, which can lead to additive impairment of psychomotor performance and cause daytime impairment.
- darifenacin
topiramate will decrease the level or effect of darifenacin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- darunavir
topiramate will decrease the level or effect of darunavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- dasatinib
topiramate will decrease the level or effect of dasatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- desflurane
desflurane and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- desipramine
desipramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- deutetrabenazine
topiramate and deutetrabenazine both increase sedation. Use Caution/Monitor.
- dexamethasone
topiramate will decrease the level or effect of dexamethasone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- dexchlorpheniramine
dexchlorpheniramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
dexchlorpheniramine and topiramate both increase sedation. Modify Therapy/Monitor Closely. - dexfenfluramine
dexfenfluramine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
topiramate increases and dexfenfluramine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
phentermine and dexfenfluramine both decrease sedation. Use Caution/Monitor. - dexmedetomidine
dexmedetomidine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
dexmedetomidine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - dexmethylphenidate
topiramate increases and dexmethylphenidate decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
dexmethylphenidate and phentermine both decrease sedation. Use Caution/Monitor.
dexmethylphenidate and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. - dextroamphetamine
dextroamphetamine and phentermine both decrease sedation. Use Caution/Monitor.
topiramate increases and dextroamphetamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
dextroamphetamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. - dextromoramide
dextromoramide and topiramate both increase sedation. Modify Therapy/Monitor Closely.
dextromoramide increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - diamorphine
diamorphine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
diamorphine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - diazepam
topiramate will decrease the level or effect of diazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
diazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely. - dichlorphenamide
dichlorphenamide and phentermine both decrease serum potassium. Use Caution/Monitor.
- dichlorphenamide
dichlorphenamide and topiramate both decrease serum potassium. Use Caution/Monitor.
dichlorphenamide, topiramate. Either increases levels of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Both drugs can cause metabolic acidosis. - dienogest/estradiol valerate
topiramate will decrease the level or effect of dienogest/estradiol valerate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Advise women to use alternative method of contraception or back-up method when moderate or weak enzyme inducer is used with combination contraceptives. Back-up contraception should be continued for 28 days after discontinuing medication to ensure contraceptive reliability.
- diethylpropion
diethylpropion and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
topiramate increases and diethylpropion decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
phentermine and diethylpropion both decrease sedation. Use Caution/Monitor. - difelikefalin
difelikefalin and topiramate both increase sedation. Use Caution/Monitor.
- difenoxin hcl
difenoxin hcl increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- difenoxin hcl
difenoxin hcl and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- diltiazem
phentermine will decrease the level or effect of diltiazem by pharmacodynamic antagonism. Use Caution/Monitor. Amphetamines may diminish antihypertensive effects of diltiazem. Monitor BP.
topiramate will decrease the level or effect of diltiazem by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. - dimenhydrinate
dimenhydrinate increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
dimenhydrinate and topiramate both increase sedation. Modify Therapy/Monitor Closely. - diphenhydramine
diphenhydramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
diphenhydramine and topiramate both increase sedation. Modify Therapy/Monitor Closely. - diphenoxylate hcl
diphenoxylate hcl and topiramate both increase sedation. Modify Therapy/Monitor Closely.
diphenoxylate hcl increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - dipipanone
dipipanone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
dipipanone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - dobutamine
dobutamine and phentermine both decrease sedation. Use Caution/Monitor.
topiramate increases and dobutamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
dobutamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. - dopamine
topiramate increases and dopamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
dopamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
phentermine and dopamine both decrease sedation. Use Caution/Monitor. - dopexamine
topiramate increases and dopexamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
dopexamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
dopexamine and phentermine both decrease sedation. Use Caution/Monitor. - doxepin
doxepin increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
doxepin and topiramate both increase sedation. Modify Therapy/Monitor Closely. - doxylamine
doxylamine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- droperidol
droperidol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- droperidol
droperidol and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- droxidopa
phentermine and droxidopa both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. May increase risk for supine hypertension
- eletriptan
topiramate will decrease the level or effect of eletriptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- ephedrine
ephedrine, phentermine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor.
topiramate increases and ephedrine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
ephedrine and phentermine both decrease sedation. Use Caution/Monitor.
ephedrine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. - epinephrine
epinephrine and phentermine both decrease sedation. Use Caution/Monitor.
epinephrine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
topiramate increases and epinephrine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely. - epinephrine inhaled
phentermine, epinephrine inhaled. Either increases effects of the other by sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
- epinephrine racemic
topiramate increases and epinephrine racemic decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
- epinephrine racemic
epinephrine racemic and phentermine both decrease sedation. Use Caution/Monitor.
epinephrine racemic and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. - erlotinib
topiramate will decrease the level or effect of erlotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- esketamine intranasal
esketamine intranasal, topiramate. Either increases toxicity of the other by sedation. Modify Therapy/Monitor Closely.
esketamine intranasal, phentermine. Either increases toxicity of the other by sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. Closely monitor blood pressure with concomitant use of esketamine nasal with stimulants. . - estazolam
estazolam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
estazolam and topiramate both increase sedation. Modify Therapy/Monitor Closely. - estradiol
topiramate will decrease the level or effect of estradiol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- ethanol
ethanol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- estrogens conjugated synthetic
topiramate will decrease the level or effect of estrogens conjugated synthetic by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- estrogens esterified
topiramate will decrease the level or effect of estrogens esterified by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Topiramate may compromise the efficacy of estrogens used for contraception or hormone replacement therapies
- estropipate
topiramate will decrease the level or effect of estropipate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- ethanol
ethanol and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- etonogestrel
topiramate will decrease the level or effect of etonogestrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- etravirine
topiramate will decrease the level or effect of etravirine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- eucalyptus
eucalyptus and topiramate both increase sedation. Use Caution/Monitor.
- felodipine
topiramate will decrease the level or effect of felodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- fenfluramine
fenfluramine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
topiramate increases and fenfluramine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
phentermine and fenfluramine both decrease sedation. Use Caution/Monitor. - fesoterodine
topiramate will decrease the level or effect of fesoterodine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- fluphenazine
fluphenazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
fluphenazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only. - fludrocortisone
topiramate will decrease the level or effect of fludrocortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- fluphenazine
fluphenazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- flurazepam
flurazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely.
flurazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - formoterol
formoterol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
topiramate increases and formoterol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
formoterol and phentermine both decrease sedation. Use Caution/Monitor. - fosamprenavir
topiramate will decrease the level or effect of fosamprenavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- green tea
green tea, phentermine. Other (see comment). Use Caution/Monitor. Comment: Green tea may include caffeine. Caffeine is a CNS-stimulant and additive effects may be seen when coadministered with other CNS stimulants. Caffeine should be avoided or used cautiously.
- fosaprepitant
topiramate will decrease the level or effect of fosaprepitant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- fosphenytoin
fosphenytoin decreases levels of topiramate by increasing metabolism. Use Caution/Monitor.
- ganaxolone
topiramate and ganaxolone both increase sedation. Use Caution/Monitor.
- haloperidol
haloperidol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
haloperidol and topiramate both increase sedation. Modify Therapy/Monitor Closely. - hydralazine
hydralazine, phentermine. Mechanism: pharmacodynamic antagonism. Use Caution/Monitor. Sympathomimetics can antagonize the activity of some antihypertensive agents.
- hydrocortisone
topiramate will decrease the level or effect of hydrocortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- hydromorphone
hydromorphone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
hydromorphone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - hydroxyprogesterone caproate (DSC)
topiramate will decrease the level or effect of hydroxyprogesterone caproate (DSC) by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- hydroxyzine
hydroxyzine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- hydroxyzine
hydroxyzine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- iloperidone
iloperidone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
topiramate will decrease the level or effect of iloperidone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
iloperidone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - imipramine
imipramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
imipramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - indinavir
topiramate will decrease the level or effect of indinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- ioflupane I 123
phentermine decreases effects of ioflupane I 123 by receptor binding competition. Use Caution/Monitor. Drugs that bind to dopamine transporter receptor with high affinity may interfere with the image following ioflupane I 123 administration.
- isavuconazonium sulfate
topiramate will decrease the level or effect of isavuconazonium sulfate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- isoproterenol
isoproterenol and phentermine both decrease sedation. Use Caution/Monitor.
topiramate increases and isoproterenol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
isoproterenol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. - ketamine
ketamine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- ketotifen, ophthalmic
ketotifen, ophthalmic increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- ketotifen, ophthalmic
ketotifen, ophthalmic and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- lacosamide
topiramate increases toxicity of lacosamide by Other (see comment). Use Caution/Monitor. Comment: Coadministration of lacosamide with sodium channel-blocking antiseizure drugs may increase the risk for AV block, bradycardia, or ventricular tachyarrhythmias. Monitor ECG before beginning lacosamide and after lacosamide is titrated to steady-state.
- lapatinib
topiramate will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- lasmiditan
lasmiditan, topiramate. Either increases effects of the other by sedation. Use Caution/Monitor. Coadministration of lasmiditan and other CNS depressant drugs, including alcohol have not been evaluated in clinical studies. Lasmiditan may cause sedation, as well as other cognitive and/or neuropsychiatric adverse reactions.
- lemborexant
lemborexant will increase the level or effect of topiramate by sedation. Modify Therapy/Monitor Closely. Dosage adjustment may be necessary if lemborexant is coadministered with other CNS depressants because of potentially additive effects.
- levalbuterol
topiramate increases and levalbuterol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
levalbuterol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
levalbuterol and phentermine both decrease sedation. Use Caution/Monitor. - levonorgestrel intrauterine
topiramate decreases levels of levonorgestrel intrauterine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- levorphanol
levorphanol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- levonorgestrel oral
topiramate decreases levels of levonorgestrel oral by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- levonorgestrel oral/ethinylestradiol/ferrous bisglycinate
topiramate will decrease the level or effect of levonorgestrel oral/ethinylestradiol/ferrous bisglycinate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. The efficacy of hormonal contraceptives may be reduced. Use an alternative method of contraception or a backup method when enzyme inducers are used with combined hormonal contraceptives (CHCs), and continue backup contraception for 28 days after discontinuing enzyme inducer to ensure contraceptive reliability.
- levorphanol
levorphanol and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- linagliptin
topiramate will increase the level or effect of linagliptin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Use of alternative treatments is strongly recommended when linagliptin is to be administered with a CYP3A4 inducer
- lisdexamfetamine
lisdexamfetamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
lisdexamfetamine and phentermine both decrease sedation. Use Caution/Monitor.
topiramate increases and lisdexamfetamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely. - lithium
topiramate increases levels of lithium by unspecified interaction mechanism. Use Caution/Monitor. Increase in lithium exposure may occur with doses of up to 600 mg/day; monitor lithium levels when coadministered with high-dose topiramate .
- lofepramine
lofepramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- lofepramine
lofepramine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- lofexidine
lofexidine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
lofexidine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - lopinavir
topiramate will decrease the level or effect of lopinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- loprazolam
loprazolam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- loprazolam
loprazolam and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- loratadine
topiramate will decrease the level or effect of loratadine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- lorazepam
lorazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely.
lorazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - lormetazepam
lormetazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely.
lormetazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - loxapine
loxapine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
loxapine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - loxapine inhaled
loxapine inhaled and topiramate both increase sedation. Modify Therapy/Monitor Closely.
loxapine inhaled increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - lumefantrine
topiramate will decrease the level or effect of lumefantrine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- maprotiline
maprotiline increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- lurasidone
lurasidone, topiramate. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: Potential for increased CNS depressant effects when used concurrently; monitor for increased adverse effects and toxicity.
- maprotiline
maprotiline and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- maraviroc
topiramate will decrease the level or effect of maraviroc by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- marijuana
marijuana and topiramate both increase sedation. Modify Therapy/Monitor Closely.
marijuana increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - mavacamten
topiramate will increase the level or effect of mavacamten by affecting hepatic enzyme CYP2C19 metabolism. Modify Therapy/Monitor Closely. Inititiation of weak CYP2C19 inhibitors may require decreased mavacamten dose.
- melatonin
melatonin increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- melatonin
melatonin and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- meperidine
meperidine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
meperidine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - meprobamate
meprobamate increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
meprobamate and topiramate both increase sedation. Modify Therapy/Monitor Closely. - mestranol
topiramate will decrease the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- metaproterenol
metaproterenol and phentermine both decrease sedation. Use Caution/Monitor.
metaproterenol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. - metaproterenol
topiramate increases and metaproterenol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
- metaxalone
metaxalone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- metformin
phentermine decreases effects of metformin by pharmacodynamic antagonism. Use Caution/Monitor. Patient should be closely observed for loss of blood glucose control; when drugs are withdrawn from a patient receiving metformin, patient should be observed closely for hypoglycemia.
topiramate increases toxicity of metformin by Other (see comment). Use Caution/Monitor. Comment: Decreases serum bicarbonate and induce non-anion gap, hyperchloremic metabolic acidosis. - methadone
topiramate will decrease the level or effect of methadone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
methadone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
methadone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - methamphetamine
methamphetamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
topiramate increases and methamphetamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
methamphetamine and phentermine both decrease sedation. Use Caution/Monitor. - methazolamide
topiramate, methazolamide. Either increases toxicity of the other by pharmacodynamic synergism. Use Caution/Monitor. Increased risk of kidney stone formation.
- methyldopa
methyldopa increases effects of phentermine by unknown mechanism. Use Caution/Monitor.
- methocarbamol
methocarbamol and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- methylenedioxymethamphetamine
methylenedioxymethamphetamine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
topiramate increases and methylenedioxymethamphetamine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
methylenedioxymethamphetamine and phentermine both decrease sedation. Use Caution/Monitor. - methylphenidate transdermal
methylphenidate transdermal will increase the level or effect of topiramate by decreasing metabolism. Modify Therapy/Monitor Closely. Consider decreasing the dose of these drugs when given coadministered with methylphenidate. Monitor for drug toxiticities when initiating or discontinuing methylphenidate.
- midazolam
midazolam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- methylprednisolone
topiramate will decrease the level or effect of methylprednisolone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- midazolam
topiramate will decrease the level or effect of midazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
midazolam and topiramate both increase sedation. Modify Therapy/Monitor Closely. - midazolam intranasal
midazolam intranasal, topiramate. Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Concomitant use of barbiturates, alcohol, or other CNS depressants may increase the risk of hypoventilation, airway obstruction, desaturation, or apnea and may contribute to profound and/or prolonged drug effect.
- midodrine
topiramate increases and midodrine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
phentermine and midodrine both decrease sedation. Use Caution/Monitor.
midodrine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. - mirtazapine
mirtazapine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
mirtazapine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - modafinil
modafinil and phentermine both decrease sedation. Use Caution/Monitor.
topiramate increases and modafinil decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely. - morphine
morphine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
morphine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - motherwort
motherwort and topiramate both increase sedation. Modify Therapy/Monitor Closely.
motherwort increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - moxonidine
moxonidine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
moxonidine and topiramate both increase sedation. Modify Therapy/Monitor Closely. - nabilone
nabilone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
nabilone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - nalbuphine
nalbuphine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
nalbuphine and topiramate both increase sedation. Modify Therapy/Monitor Closely. - nelfinavir
topiramate will decrease the level or effect of nelfinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- norepinephrine
norepinephrine and phentermine both decrease sedation. Use Caution/Monitor.
norepinephrine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. - nicardipine
topiramate will decrease the level or effect of nicardipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- nilotinib
topiramate will decrease the level or effect of nilotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- nisoldipine
topiramate will decrease the level or effect of nisoldipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- norepinephrine
topiramate increases and norepinephrine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
- nortriptyline
nortriptyline and topiramate both increase sedation. Modify Therapy/Monitor Closely.
nortriptyline increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - olanzapine
olanzapine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
olanzapine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - opium tincture
opium tincture and topiramate both increase sedation. Modify Therapy/Monitor Closely.
opium tincture increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - orlistat
orlistat decreases levels of topiramate by inhibition of GI absorption. Applies only to oral form of both agents. Modify Therapy/Monitor Closely. Risk of convulsions.
- oxazepam
oxazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- orphenadrine
orphenadrine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- oxazepam
oxazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- oxycodone
oxycodone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
oxycodone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - oxymorphone
oxymorphone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
oxymorphone and topiramate both increase sedation. Modify Therapy/Monitor Closely. - oxytocin
oxytocin increases effects of phentermine by pharmacodynamic synergism. Use Caution/Monitor.
- paliperidone
paliperidone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- paliperidone
paliperidone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- papaveretum
papaveretum and topiramate both increase sedation. Modify Therapy/Monitor Closely.
papaveretum increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - papaverine
papaverine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- pentazocine
pentazocine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- pazopanib
topiramate will decrease the level or effect of pazopanib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- pentazocine
pentazocine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- pentobarbital
pentobarbital and topiramate both increase sedation. Modify Therapy/Monitor Closely.
pentobarbital increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - perphenazine
perphenazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
perphenazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
perphenazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only. - phendimetrazine
topiramate increases and phendimetrazine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
phendimetrazine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
phentermine and phendimetrazine both decrease sedation. Use Caution/Monitor. - phenobarbital
phenobarbital and topiramate both increase sedation. Modify Therapy/Monitor Closely.
phenobarbital increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - phentermine
topiramate increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
- phenylephrine
phentermine and phenylephrine both decrease sedation. Use Caution/Monitor.
phentermine and phenylephrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. - phenylephrine
topiramate increases and phenylephrine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
- phenylephrine PO
topiramate increases and phenylephrine PO decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely. .
phentermine and phenylephrine PO both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
phentermine and phenylephrine PO both decrease sedation. Use Caution/Monitor. - phenytoin
phenytoin decreases levels of topiramate by increasing metabolism. Use Caution/Monitor.
- pholcodine
pholcodine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- pholcodine
pholcodine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- pimozide
pimozide and topiramate both increase sedation. Modify Therapy/Monitor Closely.
pimozide increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - pirbuterol
pirbuterol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
pirbuterol and phentermine both decrease sedation. Use Caution/Monitor.
topiramate increases and pirbuterol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely. - prednisone
topiramate will decrease the level or effect of prednisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- primidone
primidone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- primidone
primidone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- prochlorperazine
prochlorperazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
prochlorperazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
prochlorperazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - promazine
promazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
- promethazine
promethazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- promethazine
promethazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
promethazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only. - propofol
propofol and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- propylhexedrine
phentermine and propylhexedrine both decrease sedation. Use Caution/Monitor.
phentermine and propylhexedrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
topiramate increases and propylhexedrine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely. - protriptyline
protriptyline and topiramate both increase sedation. Modify Therapy/Monitor Closely.
protriptyline increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - pseudoephedrine
phentermine and pseudoephedrine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
- quazepam
quazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- quazepam
quazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- quetiapine
quetiapine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
topiramate will decrease the level or effect of quetiapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
quetiapine and topiramate both increase sedation. Modify Therapy/Monitor Closely. - quinidine
topiramate will decrease the level or effect of quinidine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- risperidone
risperidone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- ramelteon
ramelteon and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- repaglinide
topiramate will decrease the level or effect of repaglinide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- risperidone
risperidone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- ritonavir
topiramate will decrease the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- romidepsin
topiramate will decrease the level or effect of romidepsin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- sage
sage and topiramate both increase sedation. Use Caution/Monitor.
- salmeterol
salmeterol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
topiramate increases and salmeterol decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
salmeterol and phentermine both decrease sedation. Use Caution/Monitor. - saquinavir
topiramate will decrease the level or effect of saquinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- scullcap
scullcap increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- scullcap
scullcap and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- secobarbital
secobarbital increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
secobarbital and topiramate both increase sedation. Modify Therapy/Monitor Closely. - serdexmethylphenidate/dexmethylphenidate
serdexmethylphenidate/dexmethylphenidate and phentermine both decrease sedation. Use Caution/Monitor.
serdexmethylphenidate/dexmethylphenidate and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. - sevelamer
sevelamer decreases levels of topiramate by increasing elimination. Use Caution/Monitor.
- sevoflurane
sevoflurane and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- shepherd's purse
shepherd's purse and topiramate both increase sedation. Modify Therapy/Monitor Closely.
shepherd's purse increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - solifenacin
topiramate will decrease the level or effect of solifenacin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- solriamfetol
phentermine and solriamfetol both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
- stiripentol
stiripentol, topiramate. Either increases effects of the other by sedation. Use Caution/Monitor. Concomitant use stiripentol with other CNS depressants, including alcohol, may increase the risk of sedation and somnolence.
- sufentanil
sufentanil increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
sufentanil and topiramate both increase sedation. Modify Therapy/Monitor Closely. - sunitinib
topiramate will decrease the level or effect of sunitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- tapentadol
tapentadol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- tacrolimus
topiramate will decrease the level or effect of tacrolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- tadalafil
topiramate will decrease the level or effect of tadalafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- tapentadol
tapentadol and topiramate both increase sedation. Modify Therapy/Monitor Closely.
- tazemetostat
topiramate will decrease the level or effect of tazemetostat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- temazepam
temazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
temazepam and topiramate both increase sedation. Modify Therapy/Monitor Closely. - temsirolimus
topiramate will decrease the level or effect of temsirolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- terbutaline
terbutaline and phentermine both decrease sedation. Use Caution/Monitor.
terbutaline and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. - terbutaline
topiramate increases and terbutaline decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
- theophylline
topiramate will decrease the level or effect of theophylline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- thioridazine
thioridazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
thioridazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
thioridazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - thiothixene
thiothixene and topiramate both increase sedation. Modify Therapy/Monitor Closely.
thiothixene increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - tipranavir
topiramate will decrease the level or effect of tipranavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- topiramate
topiramate increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
- tobramycin inhaled
tobramycin inhaled and topiramate both increase nephrotoxicity and/or ototoxicity. Modify Therapy/Monitor Closely. Avoid concurrent or sequential use to decrease risk for ototoxicity
- tolterodine
topiramate will decrease the level or effect of tolterodine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- tramadol
tramadol and topiramate both increase sedation. Modify Therapy/Monitor Closely.
tramadol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - trazodone
trazodone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
topiramate will decrease the level or effect of trazodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
trazodone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - triamcinolone acetonide injectable suspension
topiramate will decrease the level or effect of triamcinolone acetonide injectable suspension by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- triazolam
triazolam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
- triazolam
topiramate will decrease the level or effect of triazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
triazolam and topiramate both increase sedation. Modify Therapy/Monitor Closely. - triclofos
triclofos and topiramate both increase sedation. Modify Therapy/Monitor Closely.
triclofos increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - trifluoperazine
trifluoperazine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
trifluoperazine, phentermine. Mechanism: unknown. Use Caution/Monitor. Risk of cardiac arrhythmia or sudden death, more likely w/thioridazine than other phenothiazines. Interaction more likely in certain predisposed pts. only.
trifluoperazine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - trimipramine
trimipramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
trimipramine and topiramate both increase sedation. Modify Therapy/Monitor Closely. - triprolidine
triprolidine and topiramate both increase sedation. Modify Therapy/Monitor Closely.
triprolidine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. - ubrogepant
topiramate will decrease the level or effect of ubrogepant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Dose adjustment is recommended with concomitant use of ubrogepant and moderate and weak CYP3A4 inducers. (see Dosage Modifications)
- xylometazoline
phentermine and xylometazoline both decrease sedation. Use Caution/Monitor.
phentermine and xylometazoline both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor. - valproic acid
valproic acid, topiramate. Either increases toxicity of the other by unknown mechanism. Use Caution/Monitor. Risk of hyperammonemia with or without encephalopathy; pts. with inborn errors of metabolism may be at greater risk. S/S: altered LOC, lethargy, vomiting.
- vardenafil
topiramate will decrease the level or effect of vardenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- verapamil
topiramate will decrease the level or effect of verapamil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.
- xylometazoline
topiramate increases and xylometazoline decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely.
- yohimbine
phentermine and yohimbine both decrease sedation. Use Caution/Monitor.
phentermine and yohimbine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. Use Caution/Monitor.
topiramate increases and yohimbine decreases sedation. Effect of interaction is not clear, use caution. Modify Therapy/Monitor Closely. - ziconotide
ziconotide increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
topiramate and ziconotide both increase sedation. Modify Therapy/Monitor Closely. - ziprasidone
ziprasidone increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.
ziprasidone and topiramate both increase sedation. Modify Therapy/Monitor Closely.
Minor (71)
- acetaminophen
topiramate decreases levels of acetaminophen by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- acetaminophen IV
topiramate decreases levels of acetaminophen IV by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- acetaminophen rectal
topiramate decreases levels of acetaminophen rectal by increasing metabolism. Minor/Significance Unknown. Enhanced metabolism incr levels of hepatotoxic metabolites.
- alfentanil
topiramate will decrease the level or effect of alfentanil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- alfuzosin
topiramate will decrease the level or effect of alfuzosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- alosetron
topiramate will decrease the level or effect of alosetron by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- amantadine
amantadine, phentermine. Either increases effects of the other by pharmacodynamic synergism. Minor/Significance Unknown. Potential for additive CNS stimulation.
- American ginseng
American ginseng increases effects of phentermine by pharmacodynamic synergism. Minor/Significance Unknown.
- amobarbital
amobarbital decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown.
- armodafinil
topiramate will decrease the level or effect of armodafinil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- atazanavir
topiramate will decrease the level or effect of atazanavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- atracurium
topiramate decreases effects of atracurium by pharmacodynamic antagonism. Minor/Significance Unknown.
- biotin
topiramate decreases levels of biotin by unspecified interaction mechanism. Minor/Significance Unknown. Biotin supplementation may be necessary.
- bortezomib
topiramate will decrease the level or effect of bortezomib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown. Caution is advised with concurrent use.
- bosentan
topiramate will decrease the level or effect of bosentan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- butabarbital
butabarbital decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown.
- butalbital
butalbital decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown.
- cevimeline
topiramate will decrease the level or effect of cevimeline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- cisatracurium
topiramate decreases effects of cisatracurium by pharmacodynamic antagonism. Minor/Significance Unknown.
- clarithromycin
topiramate will decrease the level or effect of clarithromycin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- clomipramine
topiramate will decrease the level or effect of clomipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- cyanocobalamin
topiramate decreases levels of cyanocobalamin by inhibition of GI absorption. Applies only to oral form of both agents. Minor/Significance Unknown.
- dapsone
topiramate will decrease the level or effect of dapsone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- desmopressin
desmopressin increases effects of phentermine by pharmacodynamic synergism. Minor/Significance Unknown.
- dexmethylphenidate
dexmethylphenidate increases effects of topiramate by decreasing metabolism. Minor/Significance Unknown.
- digoxin
topiramate decreases levels of digoxin by unspecified interaction mechanism. Minor/Significance Unknown.
- disopyramide
topiramate will decrease the level or effect of disopyramide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- donepezil
topiramate will decrease the level or effect of donepezil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- dutasteride
topiramate will decrease the level or effect of dutasteride by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- efavirenz
topiramate will decrease the level or effect of efavirenz by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- eplerenone
topiramate will decrease the level or effect of eplerenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- ethotoin
topiramate increases levels of ethotoin by decreasing metabolism. Minor/Significance Unknown.
ethotoin decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown. - eucalyptus
eucalyptus increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Minor/Significance Unknown.
topiramate will decrease the level or effect of eucalyptus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown. - finasteride
topiramate will decrease the level or effect of finasteride by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- guarana
guarana increases effects of phentermine by pharmacodynamic synergism. Minor/Significance Unknown.
- fosphenytoin
topiramate increases levels of fosphenytoin by decreasing metabolism. Minor/Significance Unknown.
- galantamine
topiramate will decrease the level or effect of galantamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- glyburide
topiramate will decrease the level or effect of glyburide by unknown mechanism. Minor/Significance Unknown. Effect in glycemic control is likely small.
- imatinib
topiramate will decrease the level or effect of imatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- imipramine
topiramate will decrease the level or effect of imipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- incobotulinumtoxinA
topiramate decreases effects of incobotulinumtoxinA by pharmacodynamic antagonism. Minor/Significance Unknown.
- isradipine
topiramate will decrease the level or effect of isradipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- itraconazole
topiramate will decrease the level or effect of itraconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- ketoconazole
topiramate will decrease the level or effect of ketoconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- levocarnitine
topiramate decreases levels of levocarnitine by unspecified interaction mechanism. Minor/Significance Unknown.
- levoketoconazole
topiramate will decrease the level or effect of levoketoconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- montelukast
topiramate will decrease the level or effect of montelukast by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- nifedipine
topiramate will decrease the level or effect of nifedipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- nimodipine
topiramate will decrease the level or effect of nimodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- nitrendipine
topiramate will decrease the level or effect of nitrendipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- onabotulinumtoxinA
topiramate decreases effects of onabotulinumtoxinA by pharmacodynamic antagonism. Minor/Significance Unknown.
- ondansetron
topiramate will decrease the level or effect of ondansetron by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- oxybutynin
topiramate will decrease the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- paclitaxel
topiramate will decrease the level or effect of paclitaxel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- paclitaxel protein bound
topiramate will decrease the level or effect of paclitaxel protein bound by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- pancuronium
topiramate decreases effects of pancuronium by pharmacodynamic antagonism. Minor/Significance Unknown.
- parecoxib
topiramate will decrease the level or effect of parecoxib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- pentobarbital
pentobarbital decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown.
- phenobarbital
phenobarbital decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown.
- phenytoin
topiramate increases levels of phenytoin by decreasing metabolism. Minor/Significance Unknown.
- pimozide
topiramate will decrease the level or effect of pimozide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- pioglitazone
topiramate will decrease the level or effect of pioglitazone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- primidone
primidone decreases levels of topiramate by increasing metabolism. Minor/Significance Unknown.
- propafenone
topiramate will decrease the level or effect of propafenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- quinine
topiramate will decrease the level or effect of quinine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- ramelteon
topiramate will decrease the level or effect of ramelteon by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- rapacuronium
topiramate decreases effects of rapacuronium by pharmacodynamic antagonism. Minor/Significance Unknown.
- rocuronium
topiramate decreases effects of rocuronium by pharmacodynamic antagonism. Minor/Significance Unknown.
- sage
sage increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Minor/Significance Unknown.
sage decreases effects of topiramate by pharmacodynamic antagonism. Minor/Significance Unknown. Theoretical interaction; some species of sage may cause convulsions. - saxagliptin
topiramate will decrease the level or effect of saxagliptin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.
- yerba mate
yerba mate increases effects of phentermine by pharmacodynamic synergism. Minor/Significance Unknown.
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
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
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 registry and epidemiologic studies indicate increased risk in oral clefts (cleft lip with or without cleft palate) with first trimester exposure to topiramate, a component of the drug combination
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.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)
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
Images
Formulary
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