• Obesity

Adipex-p Generic Name & Formulations

General Description

Phentermine HCl 37.5mg; caps; scored tabs.

Pharmacological Class


How Supplied

Caps—100; Tabs—30, 100

How Supplied

Tablets are packaged in bottles of 30 and 100.

  • Each white, oblong, scored tablet is debossed with “Adipex-P” and “9”-“9”. 

Capsules are packaged in bottles of 100.

  • Each capsule has an opaque white body and an opaque bright blue cap. Each capsule is imprinted with “Adipex-P” - “37.5” on the cap and two stripes on the body using dark blue ink. 


Store at 20° to 25° C (68° to 77° F).


Generic Availability


Adipex-p Indications


A short-term (a few weeks) adjunct in a regimen of weight reduction based on exercise, behavioral modification and caloric restriction in the management of exogenous obesity for patients with an initial body mass index ≥30kg/m2, or ≥27kg/m2 in the presence of other risk factors (eg, hypertension, diabetes, hyperlipidemia).

Adipex-p Dosage and Administration


>16yrs: Individualize. Usual dose: 37.5mg once daily before or 1–2 hrs after breakfast, or 18.75mg 1–2 times daily. Avoid late evening dosing. Severe renal impairment (eGFR 15–29mL/min/1.73m2): max 15mg daily.


≤16yrs: not recommended.

Adipex-p Contraindications


History of cardiovascular disease (eg, coronary artery disease, stroke, arrhythmias, congestive heart failure, uncontrolled hypertension). Hyperthyroidism. Glaucoma. Agitated states. History of drug abuse. Pregnancy. Nursing. During or within 14 days of MAOIs.

Adipex-p Boxed Warnings

Not Applicable

Adipex-p Warnings/Precautions


Increased risk of primary pulmonary hypertension, valvular heart disease. Discontinue if unexplained dyspnea, angina, syncope, or lower extremity edema develops. Discontinue if tolerance to the anorectant effect develops. Mild hypertension. Diabetes. Prescribe minimal supply to avoid overdose. Renal impairment (eGFR <15mL/min/1.73m2), including ESRD requiring dialysis: avoid. Elderly.


Primary Pulmonary Hypertension (PPH)

  • PPH has been reported when phentermine was combined with fenfluramine or dexfenfluramine and with phentermine alone.
  • Advise patients to report immediately any deterioration in exercise tolerance.
  • Treatment should be discontinued in those who develop new, unexplained symptoms of dyspnea, angina pectoris, syncope or lower extremity edema, and evaluate for the possible pulmonary hypertension.

Valvular Heart Disease

  • Serious regurgitant cardiac valvular disease, primarily affecting the mitral, aortic and/or tricuspid valves, has been reported in patients who had taken a combination of phentermine with fenfluramine or dexfenfluramine. 
  • Rare cases of valvular heart disease have been reported with phentermine alone.

Development of Tolerance

  • The recommended dose should not be exceeded in an attempt to increase the effect.
  • Discontinue phentermine if tolerance to the anorectant effect develops.

Risk of Abuse and Dependence

  • Adipex-P is related chemically and pharmacologically to amphetamine (d- and dll-amphetamine) and to other related stimulant drugs that have been extensively abused. 
  • Consider the abuse potential of phentermine when evaluating the desirability of including the drug as part of a weight reduction program.


  • Use caution in patients with mild hypertension as phentermine may increase blood pressure.

Pregnancy Considerations

Adipex-P is contraindicated during pregnancy because weight loss offers no potential benefit to a pregnant woman and may result in fetal harm.

Nursing Mother Considerations

It is not known if Adipex-P is excreted in human milk; however, other amphetamines are present in human milk. Because of the potential for serious adverse reactions in nursing infants, a decision should be made whether to discontinue nursing or to discontinue the drug, taking into account the importance of the drug to the mother.

Pediatric Considerations

Safety and effectiveness in pediatric patients have not been established. The use of Adipex-P is not recommended for short-term therapy in pediatric obesity.

Geriatric Considerations

Dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.

Renal Impairment Considerations

Use caution when administering phentermine to patients with renal impairment.

Limit phentermine dose to 15mg daily in patients with severe renal impairment (eGFR 15–29mL/min/1.73m2).

Phentermine has not been studied in patients with eGFR <15mL/min/1.73m2, including end-stage renal disease requiring dialysis; avoid use in these populations.

Adipex-p Pharmacokinetics


Renal. Half-life: ~20 hours.

Adipex-p Interactions


See Contraindications. Hypertensive crisis possible with MAOIs. Concomitant weight loss drugs, including SSRIs (fluoxetine, sertraline, fluvoxamine, paroxetine), OTC and herbal products: not recommended. Caution with alcohol. Insulin or oral hypoglycemic medications requirements may be altered. May decrease hypotensive effect of adrenergic neuron blocking drugs.

Adipex-p Adverse Reactions

Adverse Reactions

Primary pulmonary hypertension, regurgitant cardiac valvular disease, palpitation, tachycardia, elevated blood pressure, ischemic events, overstimulation, restlessness, dizziness, insomnia, euphoria, dysphoria, tremor, headache, dry mouth, unpleasant taste, GI upset, constipation, urticaria, impotence, changes in libido; rare: psychotic episodes.

Adipex-p Clinical Trials

Clinical Trials

No clinical studies have been conducted with Adipex-P.

In relatively short-term clinical trials, adult obese patients instructed in dietary management and treated with anorectic drugs lost more weight on the average than those treated with placebo and diet.

The magnitude of increased weight loss of drug-treated patients over patients given placebo is only a fraction of a pound a week. The rate of weight loss is greatest in the first weeks of therapy for both drug and placebo patients and tends to decrease in succeeding weeks. 

The natural history of obesity is measured over several years, whereas the studies cited are restricted to a few weeks’ duration; thus, the total impact of drug-induced weight loss over that of diet alone must be considered clinically limited.

Adipex-p Note

Not Applicable

Adipex-p Patient Counseling

Patient Counseling

Inform patients that Adipex-P should be used only for a short period of time (a few weeks) as an adjunct to a weight reduction program based on exercise, behavioral modification, and caloric restriction.

Advise pregnant women and nursing mothers not to use Adipex-P.

Inform patients about the risks associated with phentermine use (eg, PPH, valvular heart disease, effects on the ability to engage in potentially hazardous tasks, increased BP, drug interactions); also, the potential for developing tolerance, the risk of dependence, and consequences of abuse.

Advise patients that Adipex-P should be kept in a safe place to prevent theft, accidental overdose, misuse or abuse.