Benzphetamine Hydrochloride

Pronunciation: (benz-FET-a-meen HYE-droe-KLOR-ide)
Class: Anorexiant

Trade Names

Didrex
- Tablets 50 mg

Pharmacology

Stimulates satiety center in brain, causing appetite suppression.

Pharmacokinetics

Pharmacokinetic information not available.

Indications and Usage

For the management of exogenous obesity as a short-term (few weeks) adjunct to a diet plan to reduce weight.

Contraindications

Hypersensitivity to sympathomimetic amines; pregnancy; advanced arteriosclerosis; symptomatic CV disease; moderate to severe hypertension; hyperthyroidism; glaucoma; agitated states; history of drug abuse; during or within 14 days of MAOI use; coadministration with other CNS stimulants.

Dosage and Administration

Adults and Children 12 yr of age and older

PO 25 to 50 mg once daily initially, with subsequent increase in dose or frequency according to response. Usual dosage is 25 to 50 mg 1 to 3 times daily.

General Advice

• A single daily dose is preferably given mid-morning or mid-afternoon, according to the patient's eating habits. In an occasional patient, it may be desirable to avoid late afternoon administration.
• Continue treatment only if the patient has a satisfactory weight loss within the first 4 wk of treatment (ie, weight loss of at least 1.8 kg or as determined by the health care provider).

Storage/Stability

Store at 68° to 77°F.

Drug Interactions

Anorectic agents (eg, sibutramine)

Do not use benzphetamine with other anorectic agents, including prescribed drugs, nonprescription drugs, and herbal products. The risk of serious cardiac problems may be increased.

Antihypertensive agents

The hypotensive effect of antihypertensive agents may be increased. Use with caution. Carefully monitor BP and adjust the antihypertensive dose as needed.

CNS stimulants (eg, amphetamine)

Additive CNS effects. Do not use benzphetamine with other CNS stimulants.

Insulin

Insulin requirements in diabetes mellitus may be altered in association with use of anorexigenic drugs and the concomitant dietary restrictions. Monitor blood glucose and adjust the insulin dose as needed.

Iobenguane

Benzphetamine may reduce retention and diagnostic efficacy of iobenguane, resulting in a false-negative iobenguane imaging test. Discontinuation of benzphetamine approximately 5 biological half-lives (approximately 72 h) prior to iobenguane administration is recommended.

MAOIs (eg, phenelzine)

May cause hypertensive crisis and intracranial hemorrhage. Coadministration is contraindicated. Do not use concomitantly or within 14 days following the use of MAOIs.

SSRIs (eg, fluoxetine)

Sympathomimetic effects of benzphetamine may be increased; increased risk of serotonin syndrome. Use with caution. Monitor for signs and symptoms of increased CNS effects and serotonin syndrome. Serotonin syndrome requires immediate medical attention, including withdrawal of the serotonergic agent and supportive care.

Tricyclic antidepressants (eg, amitriptyline)

The effects of tricyclic antidepressants may be increased. Use with caution. Carefully monitor the clinical response and adjust the tricyclic antidepressant dose as needed.

Urinary acidifiers (eg, ammonium chloride)

Benzphetamine concentrations may be reduced and urinary excretion may be increased, decreasing the pharmacologic effects. Avoid agents that may acidify the urine, except in the treatment of overdosage.

Urinary alkalinizers (eg, sodium bicarbonate)

Benzphetamine concentrations may be elevated and urinary excretion may be decreased, increasing the pharmacologic effects and risk of adverse reactions. Avoid agents that may alkalinize the urine, especially in overdose situations.

Adverse Reactions

Cardiovascular

Cardiomyopathy and ischemic cardiac events with long-term use, hypertension, palpitations, tachycardia.

CNS

Changes in libido, dizziness, headache, insomnia, overstimulation, psychotic episodes, restlessness, tremor.

Dermatologic

Sweating, urticaria.

GI

Diarrhea, dry mouth, nausea, unpleasant taste.

Precautions

Monitor Consider baseline cardiac evaluation to detect preexisting valvular heart diseases or pulmonary hypertension prior to initiation. Echocardiogram during and after treatment could be useful for detecting any valvular disorders that may occur.

Pregnancy

Category X .

Lactation

Undetermined.

Children

Not recommended for children younger than 12 yr of age.

Hazardous Tasks

May impair the ability to engage in potential hazardous activities.

Cardiac effects

Pulmonary hypertension and valvular heart disease may occur. Not recommended in patients with known heart murmur or valvular heart disease.

Drug dependency

High potential for dependence and abuse; tolerance may occur.

Hypertension

Use with caution, even in mild hypertension.

Psychological disturbances

May occur.

Overdosage

Symptoms

Abdominal cramps, arrhythmias, assaultiveness, circulatory collapse, coma, confusion, convulsions, depression, diarrhea, fatigue, hyperpyrexia, hypertension or hypotension, nausea, panic states, restlessness, rhabdomyolysis, tachypnea, tremor, vomiting.

Patient Information

• Caution patient that this medication must not be taken during pregnancy or when pregnancy is possible. Advise patient to use a reliable form of birth control while taking this drug.
• Explain that anorexiant effects are temporary and tolerance to medication and dependence can occur.
• Instruct patient to notify health care provider immediately if the following symptoms occur: chest pain, dizziness, nervousness, or palpitations.
• Warn patient not to drive or perform tasks that require mental alertness if dizziness or blurred vision occurs.
• Tell patient to report excessive dryness of mouth, constipation, or prolonged insomnia because dosage may need to be adjusted.
• Inform patient that weight reduction requires strict adherence to dietary restrictions.

Copyright © 2009 Wolters Kluwer Health.