Didrex (Benzphetamine),distributed by Pharmacia (subsequently acquired by Pfizer), is a stimulant. As an appetite suppressant, it usually is prescribed on a short-term basis (a few weeks), in combination with diet, to help obese individuals lose weight.

No generic forms of benzphetamine are currently on the FDA list of drugs approved for sale in the United States, although in late 2005 the FDA was asked whether it would have any problem with a new generic version that was a capsule instead of a tablet.

The benefits of Didrex tend to decrease within a few weeks and its use therefore is not recommended beyond that period.

Benzphetamine is a sympathomimetic amine, which is similar to an amphetamine. It is also known as an "anorectic" or an "anorexigenic" drug. Benzphetamine stimulates the central nervous system (nerves and brain), which increases heart rate and blood pressure and decreases appetite.

WARNINGS:

When tolerance to the anorectic effect develops, the recommended dose should not be exceeded in an attempt to increase the effect; rather, the drug should be discontinued.

PRECAUTIONS:

General: Insulin requirements in diabetes mellitus may be altered in association with use of anorexigenic drugs and the concomitant dietary restrictions.

Psychological disturbances have been reported in patients who receive an anorectic agent together with a restrictive dietary regime. Caution is to be exercised in prescribing amphetamines for patients with even mild hypertension. The least amount feasible should be prescribed or dispensed at one time in order to minimize the possibility of overdosage.

Drug Interaction:

Hypertensive crises have resulted when sympathomimetic amines have been used concomitantly or within 14 days following use of monoamine oxidase inhibitors. Benzphetamine Hydrochloride Capsules should not be used concomitantly with other CNS stimulants.

Amphetamines may decrease the hypotensive effect of antihypertensives. Amphetamines may enhance the effects of tricyclic antidepressants. Urinary alkalinizing agents increase blood levels and decrease excretion of amphetamines. Urinary acidifying agents decrease blood levels and increase excretion of amphetamines.

Drug Abuse and Dependence:

Benzphetamine is a controlled substance under the Controlled Substance Act by the Drug Enforcement Administration and has been assigned to Schedule III.

Benzphetamine hydrochloride is related chemically and pharmacologically to the amphetamines. Amphetamines and related stimulant drugs have been extensively abused, and the possibility of abuse of Benzphetamine Hydrochloride Capsules should be kept in mind when evaluating the desirability of including a drug as part of a weight reduction program.

Abuse of amphetamines and related drugs may be associated with intense psychological dependence and severe social dysfunction.

There are reports of patients who have increased the dosage to many times that recommended. Abrupt cessation following prolonged high dosage administration results in extreme fatigue and mental depression; changes are also noted on the sleep EEG.

Manifestations of chronic intoxication with anorectic drugs include severe dermatoses, marked insomnia, irritability, hyperactivity, and personality changes. The most severe manifestation of chronic intoxication is psychosis, often clinically indistinguishable from schizophrenia.