AdultPediatricDosage Forms & Strengths capsule, HCl salt: Schedule IV 15mg (generics) 30mg (generics) 37.5mg (Adipex P, generics) tablet, HCl salt: Schedule IV 8mg (Lomaira) 37.5mg (Adipex P, generics) Obesity Short-term (few weeks) adjunctive use as part of weight-reduction regimen based on exercise, behavioral modification, and caloric restriction in management of exogenous obesity for patients with initial body mass index (BMI) ≥30 kg/m² or ≥27 kg/m² in presence of other risk factors (eg, controlled hypertension, diabetes, hyperlipidemia) Adjust dosing according to patient's needs to achieve adequate response with lowest effective dosage Adipex P or generic 15-37.5 mg/day PO in single daily dose or divided q12hr before breakfast or 1-2 hr after breakfast Lomaira Typical dose is 8mg PO TID 30 minutes before meals Dosage Forms & Strengths capsule, HCl salt: Schedule IV 15mg (generics) 30mg (generics) 37.5mg (Adipex P, generics) tablet, HCl salt: Schedule IV 8mg (Lomaira) 37.5mg (Adipex P, generics) Obesity Short-term (few weeks) adjunctive use as part of weight-reduction regimen based on exercise, behavioral modification, and caloric restriction in management of exogenous obesity for patients with initial BMI ≥30 kg/m² or ≥27 kg/m² in presence of other risk factors (eg, controlled hypertension, diabetes, hyperlipidemia) <16 years: Safety and efficacy not established ≥16 years Adjust dosing according to patient's needs to achieve adequate response with lowest effective dosage Adipex P or generic 15-37.5 mg/day PO in single daily dose or divided q12hr before breakfast or 1-2 hr after breakfast Lomaira Typical dose is 8mg PO TID 30 minutes before meals Interaction CheckerEnter a drug name and phentermineNo Results No Interactions Found Interactions FoundContraindicatedSerious - Use AlternativeSignificant - Monitor CloselyMinorAll Interactions Sort By: SeverityName Contraindicated (8)iobenguane I 123phentermine 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.isocarboxazidisocarboxazid increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.linezolidlinezolid increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.methylphenidatephentermine increases effects of methylphenidate by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.phenelzinephenelzine increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.procarbazineprocarbazine increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.selegiline transdermalselegiline transdermal increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.tranylcyprominetranylcypromine increases effects of phentermine by pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.Serious - Use Alternative (40)amitriptylineamitriptyline, 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.amoxapineamoxapine, 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.cabergolinecabergoline, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.citalopramcitalopram, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.clomipramineclomipramine, 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.desfluranedesflurane increases toxicity of phentermine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.desipraminedesipramine, 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.dihydroergotaminedihydroergotamine, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.dihydroergotamine intranasaldihydroergotamine intranasal, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.doxapramdoxapram increases effects of phentermine by pharmacodynamic synergism. Avoid or Use Alternate Drug. Additive pressor effect.doxepindoxepin, 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.duloxetineduloxetine, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.ergoloid mesylatesergoloid mesylates, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.ergotamineergotamine, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.escitalopramescitalopram, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.etherether increases toxicity of phentermine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.fluoxetinefluoxetine, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.fluvoxaminefluvoxamine and phentermine both increase serotonin levels. Avoid or Use Alternate Drug.imipramineimipramine, 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 131phentermine 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.isofluraneisoflurane increases toxicity of phentermine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.levomilnacipranlevomilnacipran and phentermine both increase serotonin levels. Avoid or Use Alternate Drug.lofepraminelofepramine, 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.maprotilinemaprotiline, 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.methoxyfluranemethoxyflurane increases toxicity of phentermine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.methylergonovinemethylergonovine, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Additive vasospasm; risk of hypertension.milnacipranmilnacipran, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.nefazodonenefazodone, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.nortriptylinenortriptyline, 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.ozanimodozanimod 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.paroxetineparoxetine, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.protriptylineprotriptyline, 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.rasagilinerasagiline 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. .selegilineselegiline 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. .sertralinesertraline, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.sevofluranesevoflurane increases toxicity of phentermine by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of V tach, HTN.trazodonetrazodone, 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.trimipraminetrimipramine, 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.venlafaxinevenlafaxine, phentermine. Either increases toxicity of the other by Mechanism: unknown. Avoid or Use Alternate Drug. Risk of serotonin syndrome.yohimbeyohimbe, phentermine. Mechanism: pharmacodynamic synergism. Contraindicated. Risk of acute hypertensive episode.Monitor Closely (163)albuterolalbuterol 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.alfentanilalfentanil increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.alprazolamalprazolam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.amitriptylineamitriptyline increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.amobarbitalamobarbital increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.amoxapineamoxapine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.arformoterolarformoterol 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.aripiprazolearipiprazole increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.armodafinilarmodafinil and phentermine both decrease sedation. Use Caution/Monitor.azelastineazelastine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.belladonna and opiumbelladonna and opium increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.benazeprilphentermine decreases effects of benazepril by pharmacodynamic antagonism. Use Caution/Monitor.benperidolbenperidol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.benzphetaminephentermine 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.bromocriptinebromocriptine, phentermine. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Hypertension, V tach.brompheniraminebrompheniramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.buprenorphine buccalbuprenorphine buccal increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.butabarbitalbutabarbital increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.butalbitalbutalbital increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.butorphanolbutorphanol increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.caffeinecaffeine and phentermine both decrease sedation. Use Caution/Monitor.captoprilphentermine decreases effects of captopril by pharmacodynamic antagonism. Use Caution/Monitor. Phentermine may decrease the antihypertensive effect of ACE Inhibitors.carbinoxaminecarbinoxamine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.chloral hydratechloral hydrate increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.chlordiazepoxidechlordiazepoxide increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.chlorpheniraminechlorpheniramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.chlorpromazinechlorpromazine 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.cinnarizinecinnarizine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.clemastineclemastine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.clomipramineclomipramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.clonazepamclonazepam increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.clorazepateclorazepate increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.clozapineclozapine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.codeinecodeine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.cyclizinecyclizine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.cyproheptadinecyproheptadine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.desipraminedesipramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.dexchlorpheniraminedexchlorpheniramine increases and phentermine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.dexfenfluraminephentermine 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.dexmedetomidinedexmedetomidine increases and phentermine