phentermine/topiramate (Rx)

Brand and Other Names:Qsymia
  • Print

Dosing & Uses

AdultPediatric

Dosing Forms & Strengths

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

capsule: Schedule IV

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

Weight Managetment

Adjunct to reduced-calorie diet and exercise

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

If a patient has not lost at least 3% of baseline body weight on 7.5 mg/46 mg, discontinue or escalate dose, as it is unlikely that the patient will achieve and sustain clinically meaningful weight loss at the 7.5 mg/46 mg dose

To escalate the dose: Increase to 11.25 mg/69 mg PO qDay for 14 days; followed by dosing 15 mg/92 mg qDay; evaluate weight loss following dose escalation to 15 mg/92 mg after an additional 12 weeks of treatment

If a patient has not lost at least 5% of baseline body weight on 15 mg/92 mg, discontinue as directed (ie, gradually), 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

Administration

Take once daily in the morning with or without food

Avoid dosing in the evening due to the possibility of insomnia

Discontinue 15 mg/92 mg gradually by taking a dose every other day for at least 1 week prior to stopping treatment altogether, due to the possibility of precipitating a seizure

Renal & Hepatic Impairment

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

Safety and efficacy not established

Next:

Interactions

Interaction Checker

and phentermine/topiramate

No Results

     activity indicator 
    No Interactions Found
    Interactions Found

    Contraindicated

      Serious - Use Alternative

        Significant - Monitor Closely

          Minor

            All Interactions Sort By:
             activity indicator 

            Contraindicated (8)

            • iobenguane I 123

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

            • isocarboxazid

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

            • linezolid

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

            • methylphenidate

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

            • phenelzine

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

            • procarbazine

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

            • selegiline transdermal

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

            • tranylcypromine

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

            Serious - Use Alternative (40)

            • 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.

            • 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

              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.

            • doxapram

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

            • 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

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

            • escitalopram

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

            • ether

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

            • 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.

            • 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.

            • 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.

            • 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.

            • 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.

            • paroxetine

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

            • 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.

            • 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.

            • 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.

            • venlafaxine

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

            • yohimbe

              yohimbe, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.

            Monitor Closely (163)

            • albuterol

              albuterol and phentermine both decrease sedation. Use Caution/Monitor.

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

            • alfentanil

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

            • alprazolam

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

            • amitriptyline

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

            • amobarbital

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

            • amoxapine

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

            • 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.

            • aripiprazole

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

            • armodafinil

              armodafinil and phentermine both decrease sedation. Use Caution/Monitor.

            • azelastine

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

            • belladonna and opium

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

            • benzphetamine

              phentermine and benzphetamine both decrease sedation. Use Caution/Monitor.

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

            • bromocriptine

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

            • brompheniramine

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

            • buprenorphine buccal

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

            • butabarbital

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

            • butalbital

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

            • butorphanol

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

            • caffeine

              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.

            • carbinoxamine

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

            • chloral hydrate

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

            • chlordiazepoxide

              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.

            • chlorpromazine

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

              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.

            • cinnarizine

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

            • clemastine

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

            • clomipramine

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

            • clonazepam

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

            • clorazepate

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

            • clozapine

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

            • codeine

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

            • cyclizine

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

            • cyproheptadine

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

            • desipramine

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

            • dexchlorpheniramine

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

            • dexfenfluramine

              phentermine and dexfenfluramine both decrease sedation. Use Caution/Monitor.

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

            • dexmedetomidine

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

            • dexmethylphenidate

              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.

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

            • dextromoramide

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

            • diamorphine

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

            • dichlorphenamide

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

            • diethylpropion

              phentermine and diethylpropion both decrease sedation. Use Caution/Monitor.

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

            • difenoxin hcl

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

            • 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.

            • dimenhydrinate

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

            • diphenhydramine

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

            • diphenoxylate hcl

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

            • dipipanone

              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.

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

            • dopamine

              phentermine and dopamine both decrease sedation. Use Caution/Monitor.

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

            • dopexamine

              dopexamine and phentermine both decrease sedation. Use Caution/Monitor.

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

            • doxepin

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

            • droperidol

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

            • 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

            • ephedrine

              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.

              ephedrine, phentermine. Either increases effects of the other by pharmacodynamic synergism. 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.

            • 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

              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.

            • esketamine intranasal

              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.

            • ethanol

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

            • fenfluramine

              phentermine and fenfluramine both decrease sedation. Use Caution/Monitor.

              fenfluramine and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. 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.

            • flurazepam

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

            • formoterol

              formoterol and phentermine both decrease sedation. Use Caution/Monitor.

              formoterol and phentermine both increase sympathetic (adrenergic) effects, including increased blood pressure and heart rate. 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.

            • haloperidol

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

            • hydralazine

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

            • hydromorphone

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

            • hydroxyzine

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

            • iloperidone

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

            • imipramine

              imipramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. 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.

            • isoproterenol

              isoproterenol and phentermine both decrease sedation. Use Caution/Monitor.

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

            • ketotifen, ophthalmic

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

            • levalbuterol

              levalbuterol and phentermine both decrease sedation. Use Caution/Monitor.

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

            • levorphanol

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

            • lisdexamfetamine

              lisdexamfetamine and phentermine both decrease sedation. Use Caution/Monitor.

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

            • lofepramine

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

            • lofexidine

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

            • loprazolam

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

            • lorazepam

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

            • lormetazepam

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

            • loxapine

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

            • loxapine inhaled

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

            • maprotiline

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

            • marijuana

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

            • melatonin

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

            • meperidine

              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.

            • 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.

            • 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.

            • methadone

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

            • methamphetamine

              methamphetamine and phentermine both decrease sedation. Use Caution/Monitor.

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

            • methyldopa

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

            • methylenedioxymethamphetamine

              methylenedioxymethamphetamine and phentermine both decrease sedation. Use Caution/Monitor.

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

            • midazolam

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

            • midodrine

              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 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.

            • morphine

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

            • motherwort

              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.

            • nabilone

              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.

            • 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.

            • nortriptyline

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

            • olanzapine

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

            • opium tincture

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

            • oxazepam

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

            • oxycodone

              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.

            • oxytocin

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

            • paliperidone

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

            • papaveretum

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

            • pentazocine

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

            • pentobarbital

              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, 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

              phentermine and phendimetrazine both decrease sedation. Use Caution/Monitor.

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

            • phenobarbital

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

            • 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 PO

              phentermine and phenylephrine PO both decrease sedation. Use Caution/Monitor.

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

            • pholcodine

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

            • pimozide

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

            • pirbuterol

              pirbuterol and phentermine both decrease sedation. Use Caution/Monitor.

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

            • primidone

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

            • prochlorperazine

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

              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.

            • 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 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.

            • 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.

            • protriptyline

              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 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.

            • risperidone

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

            • salmeterol

              salmeterol and phentermine both decrease sedation. Use Caution/Monitor.

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

            • scullcap

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

            • secobarbital

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

            • 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.

            • shepherd's purse

              shepherd's purse increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

            • solriamfetol

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

            • sufentanil

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

            • tapentadol

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

            • temazepam

              temazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. 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.

            • thioridazine

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

              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.

            • thiothixene

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

            • topiramate

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

            • tramadol

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

            • trazodone

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

            • triazolam

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

            • triclofos

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

            • trifluoperazine

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

              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.

            • trimipramine

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

            • triprolidine

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

            • 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.

            • 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.

            • ziconotide

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

            • ziprasidone

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

            Minor (7)

            • 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.

            • desmopressin

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

            • eucalyptus

              eucalyptus increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Minor/Significance Unknown.

            • guarana

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

            • sage

              sage increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Minor/Significance Unknown.

            • yerba mate

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

            Previous
            Next:

            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
            Previous
            Next:

            Warnings

            Contraindications

            Hypersensitivity or idiosyncrasy to sympathomimetic amines

            Pregnancy

            Glaucoma

            Hyperthyroidism

            Within 14 days following MAOIs (risk hypertensive crisis)

            Cautions

            May cause fetal harm (see Contraindications; see Pregnancy & Lactation)

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

            Antiepileptic drugs (AEDs), including topiramate, increase the risk of suicidal thoughts or behavior

            Acute myopia associated with secondary angle closure glaucoma has been reported with topiramate; monitor for increased IOP due to risk of permanent loss of vision; discontinue therapy in patients with ocular pain or acute onset of decreased visual acuity

            May cause mood disorders, including depression, and anxiety, as well as insomnia; patient with history of depression may be at increased risk of recurrent depression or other mood disorders

            Cognitive dysfunction (eg, impairment of concentration/attention, difficulty with memory, and speech or language problems, particularly word-finding difficulties) reported; rapid titration or high initial doses may be associated with higher rates; may need to reduce dose or discontinue therapy

            Hyperchloremic, nonanion gap, and metabolic acidosis reported; monitor serum electrolytes and bicarbonate prior to and during treatment; reduce dose or discontinue use if persistent metabolic acidosis develops

            Increase in serum creatinine that reflects a decrease in renal function (glomerular filtration rate) reported; peak increases were observed in clinical trials after 4-8 weeks of treatment and gradually declined but remained elevated over baseline values

            Weight loss may increase the risk of hypoglycemia in patients with type 2 diabetes mellitus treated with insulin and/or insulin secretagogues; monitor for needed diabetic therapy adjustments

            In patients treated for hypertension, weight loss may increase the risk of hypotension; monitor for needed antihypertensive dose adjustments

            Coadministration with alcohol or CNS depressants drugs with phentermine or topiramate may potentiate CNS depression or other centrally mediated effects of these agents (eg, dizziness, cognitive adverse reactions, drowsiness, light-headedness, impaired coordination, somnolence)

            Abrupt withdrawal of topiramate associated with seizures in individuals without a history of seizures or epilepsy; gradually discontinue if taking 15 mg/92 mg

            Caution with renal or hepatic impairment and adjust dose (see Renal & Hepatic Impairment)

            Kidney stone formation reported; topiramate inhibits carbonic anhydrase activity and promotes kidney stone formation by reducing urinary citrate excretion and increasing urine pH; avoid coadministration with other carbonic anhydrase inhibitors; use in patients on a ketogenic diet may also increase this risk; increase fluid intake to decrease risk

            Oligohidrosis (resulting in hyperthermia) reported with topiramate; use caution and monitor patients receiving carbonic anhydrase inhibitors and drugs with anticholinergic effects, or during exposure to high environmental temperatures or stenuous exercise

            Can cause changes in laboratory values; can increase the risk of hypokalemia through its inhibition of carbonic anhydrase activity; caution with coadministration of drug that cause hypokalemia (eg, furosemide, hydrochlorothiazide)

            Obtain blood chemistry profile that includes bicarbonate, creatinine, potassium, and glucose at baseline and periodically during treatment

            Use with combination oral contraceptives may increase frequency of irregular bleeding/spotting; need not discontinue unless spotting is trouble to patient

            Consider dose reduction in patients with hepatic impairment; use with caution

            Previous
            Next:

            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.

            Previous
            Next:

            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)
            Previous
            Next:

            Images

            No images available for this drug.
            Previous
            Next:

            Patient Handout

            A Patient Handout is not currently available for this monograph.
            Previous
            Next:

            Formulary

            FormularyPatient Discounts

            Adding plans allows you to compare formulary status to other drugs in the same class.

            To view formulary information first create a list of plans. Your list will be saved and can be edited at any time.

            Adding plans allows you to:

            • View the formulary and any restrictions for each plan.
            • Manage and view all your plans together – even plans in different states.
            • Compare formulary status to other drugs in the same class.
            • Access your plan list on any device – mobile or desktop.

            The above information is provided for general informational and educational purposes only. Individual plans may vary and formulary information changes. Contact the applicable plan provider for the most current information.

            Tier Description
            1 This drug is available at the lowest co-pay. Most commonly, these are generic drugs.
            2 This drug is available at a middle level co-pay. Most commonly, these are "preferred" (on formulary) brand drugs.
            3 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs.
            4 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            5 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            6 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            NC NOT COVERED – Drugs that are not covered by the plan.
            Code Definition
            PA Prior Authorization
            Drugs that require prior authorization. This restriction requires that specific clinical criteria be met prior to the approval of the prescription.
            QL Quantity Limits
            Drugs that have quantity limits associated with each prescription. This restriction typically limits the quantity of the drug that will be covered.
            ST Step Therapy
            Drugs that have step therapy associated with each prescription. This restriction typically requires that certain criteria be met prior to approval for the prescription.
            OR Other Restrictions
            Drugs that have restrictions other than prior authorization, quantity limits, and step therapy associated with each prescription.
            Additional Offers
            Email to Patient

            From:

            To:

            The recipient will receive more details and instructions to access this offer.

            By clicking send, you acknowledge that you have permission to email the recipient with this information.

            Email Forms to Patient

            From:

            To:

            The recipient will receive more details and instructions to access this offer.

            By clicking send, you acknowledge that you have permission to email the recipient with this information.

            Previous
            Medscape prescription drug monographs are based on FDA-approved labeling information, unless otherwise noted, combined with additional data derived from primary medical literature.