Benzphetamine (Monograph)

Drug class: Amphetamines

Introduction

Sympathomimetic amine; a substituted amphetamine congener that is used as an anorexigenic agent.

Uses for Benzphetamine

Obesity

• Used as an adjunct to caloric restriction for short-term treatment (a few weeks) of exogenous obesity in patients with an initial BMI ≥30 kg/m² who have not responded to an appropriate weight-reducing regimen of diet and/or exercise alone.

• Indicated for use as monotherapy only.

• Weigh limited usefulness of this class of agents against possible risks.

• Guidelines from the American Gastroenterological Association (AGA) recommend the addition of pharmacologic agents in adults with obesity or overweight with weight-related complications who have had an inadequate response to lifestyle interventions. Selection of an appropriate drug or intervention should be based on the clinical profile and needs of the patient, including comorbidities, patient preferences, costs, and access.

• Given the chronic nature of weight management, long-term pharmacologic therapy is usually necessary in patients with obesity who have an inadequate response to lifestyle interventions alone. Benzphetamine is indicated only for the short-term treatment of obesity.

Benzphetamine Dosage and Administration

General

Pretreatment Screening

• Consider baseline cardiac evaluation to detect pre-existing valvular heart disease or pulmonary hypertension prior to initiation of benzphetamine treatment.

Patient Monitoring

• Echocardiogram during and after treatment could be useful for detecting any valvular disorders which may occur.

Administration

Oral Administration

Administer orally.

Dosage

Adults

Obesity

Oral

Individualize dosage according to patient response.

Manufacturer suggests an initial dosage of 25–50 mg once daily, preferably given in midmorning or midafternoon according to the patient's dietary habits; it may be desirable to avoid late afternoon administration in some patients.

May subsequently increase dose or frequency of administration based on patient response and tolerability.

Suggested dosage ranges from 25–50 mg 1–3 times daily.

The least amount feasible should be prescribed or dispensed at one time to avoid the possibility of overdosage.

Special Populations

Hepatic Impairment

Manufacturer makes no special dosage recommendations.

Renal Impairment

Manufacturer makes no special dosage recommendations.

Geriatric Patients

Manufacturer makes no special dosage recommendations.

Cautions for Benzphetamine

Contraindications

• Patients with advanced arteriosclerosis, symptomatic cardiovascular disease, moderate to severe hypertension, hyperthyroidism, known hypersensitivity or idiosyncrasy to sympathomimetic amines, and glaucoma.

• Patients who are in an agitated state or who have a history of drug abuse.

• Concomitant use or use within 14 days following monoamine oxidase inhibitors.

• Concomitant use with other CNS stimulants.

• Women who are or may become pregnant.

Warnings/Precautions

Pulmonary Hypertension

Benzphetamine should not be used in combination with other anorectic agents, including prescribed drugs, over-the-counter (OTC) preparations, and herbal products.

In a case-control epidemiological study, use of anorectic agents was associated with increased risk of developing pulmonary hypertension. Benzphetamine was not specifically studied in this case-control study.

If exertional dyspnea or unexplained symptoms of angina pectoris, syncope, or lower extremity edema occurs, discontinue benzphetamine immediately and evaluate patient for possible pulmonary hypertension.

Carefully assess potential risk of serious adverse effects such as pulmonary hypertension against potential benefit of weight loss in patients in whom benzphetamine is being considered. Consider baseline cardiac evaluation to detect pre-existing pulmonary hypertension prior to initiation of therapy.

Valvular Heart Disease

Valvular heart disease associated with use of some anorectic agents, such as fenfluramine and dexfenfluramine, reported.

Possible contributing factors include use for extended periods of time, a higher than recommended dose, and/or use in combination with other anorectic drugs.

No cases of valvulopathy have been reported when benzphetamine was used alone.

Carefully assess potential risk of serious adverse effects such as valvular heart disease against potential benefit of weight loss in patients in whom benzphetamine is being considered.

Consider baseline cardiac evaluation to detect pre-existing valvular heart disease prior to initiation of benzphetamine treatment.

Not recommended in patients with known heart murmur or valvular heart disease.

Consider performing echocardiogram during and after treatment.

Continue treatment only if patient has satisfactory weight loss within the first 4 weeks of treatment (i.e., weight loss of at least 4 pounds, or as determined by the physician and patient).

Abuse Potential, Dependence, and Tolerance

Subject to control as a schedule III (C-III) drug.

Chemically and pharmacologically related to the amphetamines. Amphetamines and related stimulant drugs have been extensively abused.

Consider possibility of abuse when evaluating whether to include benzphetamine as part of a weight reduction program.

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

Abrupt cessation following administration of prolonged high dosages results in extreme fatigue and mental depression; changes are also noted on 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.

When tolerance to anorectic effect of benzphetamine develops, do not exceed recommended dose in an attempt to increase effect; instead, discontinue drug.

Comorbid Conditions

Not recommended in severely hypertensive patients or patients with symptomatic cardiovascular disease including arrhythmias.

Caution advised when prescribing amphetamines for patients with even mild hypertension.

Recent Use of Anorectic Agents

Not recommended for patients who used any anorectic agents within the prior year.

Insulin Requirements

Insulin requirements in patients with diabetes mellitus may be altered with use of anorexigenic drugs and concomitant dietary restrictions.

Psychological Effects

Psychological disturbances reported in patients who receive an anorectic agent together with a restrictive dietary regime.

Specific Populations

Pregnancy

Benzphetamine may cause fetal toxicity when administered to pregnant women. Amphetamines have been shown to be teratogenic and embryotoxic in animals at dosages higher than the recommended human dosage. Benzphetamine is contraindicated in women who are or may become pregnant.

If benzphetamine is administered during pregnancy or if the patient becomes pregnant while receiving the drug, the patient should be informed of the potential hazard to the fetus.

Lactation

Amphetamines are excreted in human milk. Mothers taking amphetamines should be advised to refrain from nursing.

Pediatric Use

Safety and effectiveness of benzphetamine in patients <17 years of age have not been established.

Geriatric Use

Clinical studies of benzphetamine did not include sufficient numbers of subjects ≥65 years of age to establish safety and efficacy in this population. In general, 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.

Common Adverse Effects

Adverse effects have included palpitation, tachycardia, elevated blood pressure, isolated reports of cardiomyopathy and ischemic cardiac events associated with chronic use, overstimulation, restlessness, dizziness, insomnia, tremor, sweating, headache, psychotic episodes, depression following withdrawal of the drug, dryness of the mouth, unpleasant taste, nausea, diarrhea, urticaria and other allergic skin reactions, and changes in libido.

Drug Interactions

Stability

Storage

Oral

Tablets

Store at 20–25°C with excursions permitted to 15–30°C.

Actions

• A substituted amphetamine that is used as an anorexigenic agent.

• Pharmacologic activity is similar to the amphetamines and includes CNS stimulation and elevation of BP.

• Substituted amphetamines such as benzphetamine have stronger inhibitory effects on serotonin reuptake transporters.

• No primary effect on appetite has been demonstrated; anorexigenic effect may be secondary to CNS stimulation.

Advice to Patients

• Amphetamines may impair the ability of the patient to engage in potentially hazardous activities such as operating machinery or driving a motor vehicle; the patient should therefore be cautioned accordingly.

• Advise patients to inform their clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs and herbal supplements, as well as any concomitant illnesses.

• Advise women to inform their clinicians if they are or plan to become pregnant or plan to breast-feed.

• Inform patients of other important precautionary information. (See Cautions.)

Additional Information

The American Society of Health-System Pharmacists, Inc. represents that the information provided in the accompanying monograph was formulated with a reasonable standard of care, and in conformity with professional standards in the field. Readers are advised that decisions regarding use of drugs are complex medical decisions requiring the independent, informed decision of an appropriate health care professional, and that the information contained in the monograph is provided for informational purposes only. The manufacturer’s labeling should be consulted for more detailed information. The American Society of Health-System Pharmacists, Inc. does not endorse or recommend the use of any drug. The information contained in the monograph is not a substitute for medical care.

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

Benzphetamine hydrochloride is subject to control under the Federal Controlled Substances Act of 1970 as a schedule III (C-III) drug.

* available from one or more manufacturer, distributor, and/or repackager by generic (nonproprietary) name

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