Adipex-P (Page 3 of 4)

10.2 Chronic Intoxication

Manifestations of chronic intoxication with anorectic drugs include severe dermatoses, marked insomnia, irritability, hyperactivity and personality changes. The most severe manifestation of chronic intoxications is psychosis, often clinically indistinguishable from schizophrenia. See Drug Abuse and Dependence ( 9.3) .


Phentermine hydrochloride, USP is a sympathomimetic amine anorectic. It has the chemical name of α,α,-Dimethylphenethylamine hydrochloride. The structural formula is as follows:

chemical structure

C 10 H 15 N•HCl M.W. 185.7

Phentermine hydrochloride, USP is a white, odorless, hygroscopic, crystalline powder which is soluble in water and lower alcohols, slightly soluble in chloroform and insoluble in ether.

ADIPEX-P ® , an anorectic agent for oral administration, is available as a capsule or tablet containing 37.5 mg of phentermine hydrochloride, USP (equivalent to 30 mg of phentermine base).

ADIPEX-P ® Capsules contain the inactive ingredients black iron oxide, corn starch, D&C Red #33, FD&C Blue #1, gelatin, lactose monohydrate, magnesium stearate, propylene glycol, shellac, and titanium dioxide.

ADIPEX-P ® Tablets contain the inactive ingredients corn starch, lactose (anhydrous), magnesium stearate, microcrystalline cellulose, pregelatinized corn starch, and sucrose.


12.1 Mechanism of Action

ADIPEX-P ® is a sympathomimetic amine with pharmacologic activity similar to the prototype drugs of this class used in obesity, amphetamine (d- and d l l-amphetamine). Drugs of this class used in obesity are commonly known as “anorectics” or “anorexigenics.” It has not been established that the primary action of such drugs in treating obesity is one of appetite suppression since other central nervous system actions, or metabolic effects, may also be involved.

12.2 Pharmacodynamics

Typical actions of amphetamines include central nervous system stimulation and elevation of blood pressure. Tachyphylaxis and tolerance have been demonstrated with all drugs of this class in which these phenomena have been looked for.

12.3 Pharmacokinetics

Following the administration of phentermine, phentermine reaches peak concentrations (C max ) after 3.0 to 4.4 hours.

Drug Interactions

In a single-dose study comparing the exposures after oral administration of a combination capsule of 15 mg phentermine and 92 mg topiramate to the exposures after oral administration of a 15 mg phentermine capsule or a 92 mg topiramate capsule, there is no significant topiramate exposure change in the presence of phentermine. However in the presence of topiramate, phentermine C max and AUC increase 13% and 42%, respectively.

Specific Populations

Renal Impairment

Cumulative urinary excretion of phentermine under uncontrolled urinary pH conditions was 62% to 85%.

Systemic exposure of phentermine may increase up to 91%, 45%, and 22% in patients with severe, moderate, and mild renal impairment, respectively [ see Dosage and Administration ( 2.2) and Use in Specific Populations ( 8.6) ].


13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

Studies have not been performed with phentermine to determine the potential for carcinogenesis, mutagenesis or impairment of fertility.


No clinical studies have been conducted with ADIPEX-P ®.

In relatively short-term clinical trials, adult obese subjects 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 placebo-treated patients 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 subjects and tends to decrease in succeeding weeks. The possible origins of the increased weight loss due to the various drug effects are not established. The amount of weight loss associated with the use of an “anorectic” drug varies from trial to trial, and the increased weight loss appears to be related in part to variables other than the drugs prescribed, such as the physician-investigator, the population treated and the diet prescribed. Studies do not permit conclusions as to the relative importance of the drug and non-drug factors on weight loss.

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 ® Tablets are available for oral administration containing 37.5 mg phentermine hydrochloride, USP (equivalent to 30 mg phentermine base).

Each white, oblong, scored tablet is debossed with “ADIPEX-P” and “9”-“9”. Tablets are packaged in bottles of 30 (NDC 72789-175-30) .

Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature].

Dispense in a tight, light-resistant container as defined in the USP, with a child-resistant closure (as required).



Patients must be informed that ADIPEX-P ® is 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, and that coadministration of phentermine with other drugs for weight loss is not recommended [ see Indications and Usage ( 1) and Warnings and Precautions ( 5) ].

Patients must be instructed on how much ADIPEX-P ® to take, and when and how to take it [ see Dosage and Administration ( 2) ].

Advise pregnant women and nursing mothers not to use ADIPEX-P ® [ see Use in Specific Populations ( 8.1, 8.3) ].

Patients must be informed about the risks of use of phentermine (including the risks discussed in Warnings and Precautions), about the symptoms of potential adverse reactions and when to contact a physician and/or take other action. The risks include, but are not limited to:

  • Development of primary pulmonary hypertension [ see Warnings and Precautions ( 5.2) ]
  • Development of serious valvular heart disease [ see Warnings and Precautions ( 5.3) ]
  • Effects on the ability to engage in potentially hazardous tasks [ see Warnings and Precautions ( 5.5) ]
  • The risk of an increase in blood pressure [ see Warnings and Precautions ( 5.8) and Adverse Reactions ( 6) ]
  • The risk of interactions [ see Contraindications ( 4), Warnings and Precautions ( 5) and Drug Interactions ( 7) ]

See also, for example, Adverse Reactions ( 6) and Use in Specific Populations ( 8) .

The patients must also be informed about

  • the potential for developing tolerance and actions if they suspect development of tolerance [ see Warnings and Precautions ( 5.4) ] and
  • the risk of dependence and the potential consequences of abuse [ see Warnings and Precautions ( 5.6), Drug Abuse and Dependence ( 9), and Overdosage ( 10) ].

Tell patients to keep ADIPEX-P ® in a safe place to prevent theft, accidental overdose, misuse or abuse. Selling or giving away ADIPEX-P ® may harm others and is against the law.

Brands listed are the trademarks of their respective owners.

Manufactured In Croatia By:

Pliva Hrvatska d.o.o.

Zagreb, Croatia

Manufactured For:

Teva Pharmaceuticals USA, Inc.

Parsippany, NJ 07054

Rev. AB 9/2020

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