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Benzphetamine

Pronunciation

(benz FET a meen)

Index Terms

  • Benzphetamine HCl
  • Benzphetamine Hydrochloride

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product

Tablet, Oral, as hydrochloride:

Didrex: 50 mg [DSC] [scored; contains fd&c yellow #6 (sunset yellow)]

Regimex: 25 mg

Generic: 25 mg, 50 mg

Brand Names: U.S.

  • Didrex [DSC]
  • Regimex

Pharmacologic Category

  • Anorexiant
  • Central Nervous System Stimulant
  • Sympathomimetic

Pharmacology

Benzphetamine is a sympathomimetic amine with pharmacologic properties similar to the amphetamines. The mechanism of action in reducing appetite appears to be secondary to CNS effects, including stimulation of the hypothalamus to release norepinephrine.

Use: Labeled Indications

Short-term (few weeks) adjunct to caloric restriction in exogenous obesity

Pharmacotherapy for weight loss is recommended only for obese patients with a body mass index ≥30 kg/m2, or ≥27 kg/m2 in the presence of other risk factors such as hypertension, diabetes, and/or dyslipidemia or a high waist circumference; therapy should be used in conjunction with a comprehensive weight management program.

Contraindications

Hypersensitivity or idiosyncrasy to benzphetamine or other sympathomimetic amines; advanced arteriosclerosis, symptomatic cardiovascular disease, moderate-to-severe hypertension; hyperthyroidism; glaucoma; agitated states, history of drug abuse; during or within 14 days following MAO inhibitor therapy, concurrent use with other CNS stimulants; women who are or may become pregnant

Dosing: Adult

Obesity (short-term adjunct): Oral: Dose should be individualized based on patient response: Initial: 25-50 mg once daily; titrate to 25-50 mg 1-3 times/day; maximum dose: 50 mg 3 times/day

Dosing: Geriatric

Refer to adult dosing.

Dosing: Pediatric

Obesity (short-term adjunct): Children ≥12 years: Refer to adult dosing.

Dosing: Renal Impairment

No dosage adjustment provided in manufacturer’s labeling.

Dosing: Hepatic Impairment

No dosage adjustment provided in manufacturer’s labeling.

Administration

Administer without regard to meals. For patients taking a single daily dose, administer midmorning or midafternoon based on patient’s eating habits.

Dietary Considerations

Most effective when combined with a low calorie diet and behavior modification counseling. May be taken without regard to meals.

Storage

Store at room temperature of 20°C to 25°C (68°F to 77°F).

Drug Interactions

Acebrophylline: May enhance the stimulatory effect of CNS Stimulants. Avoid combination

Alkalinizing Agents: May decrease the excretion of Amphetamines. Consider therapy modification

Ammonium Chloride: May decrease the serum concentration of Amphetamines. This effect is likely due to an enhanced excretion of amphetamines in the urine. Monitor therapy

Analgesics (Opioid): Amphetamines may enhance the analgesic effect of Analgesics (Opioid). Monitor therapy

Antacids: May decrease the excretion of Amphetamines. Monitor therapy

Antihistamines: Amphetamines may diminish the sedative effect of Antihistamines. Monitor therapy

Antihypertensive Agents: Amphetamines may diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy

Antipsychotic Agents: May diminish the stimulatory effect of Amphetamines. Monitor therapy

Ascorbic Acid: May decrease the serum concentration of Amphetamines. Monitor therapy

AtoMOXetine: May enhance the hypertensive effect of Sympathomimetics. AtoMOXetine may enhance the tachycardic effect of Sympathomimetics. Monitor therapy

Bosentan: May decrease the serum concentration of CYP3A4 Substrates. Monitor therapy

Cannabinoid-Containing Products: May enhance the tachycardic effect of Sympathomimetics. Exceptions: Cannabidiol. Monitor therapy

Carbonic Anhydrase Inhibitors: May decrease the excretion of Amphetamines. Exceptions: Brinzolamide; Dorzolamide. Monitor therapy

CYP3A4 Inducers (Moderate): May decrease the serum concentration of CYP3A4 Substrates. Monitor therapy

CYP3A4 Inducers (Strong): May increase the metabolism of CYP3A4 Substrates. Management: Consider an alternative for one of the interacting drugs. Some combinations may be specifically contraindicated. Consult appropriate manufacturer labeling. Consider therapy modification

Dabrafenib: May decrease the serum concentration of CYP3A4 Substrates. Management: Seek alternatives to the CYP3A4 substrate when possible. If concomitant therapy cannot be avoided, monitor clinical effects of the substrate closely (particularly therapeutic effects). Consider therapy modification

Deferasirox: May decrease the serum concentration of CYP3A4 Substrates. Monitor therapy

Doxofylline: Sympathomimetics may enhance the adverse/toxic effect of Doxofylline. Monitor therapy

Enzalutamide: May decrease the serum concentration of CYP3A4 Substrates. Management: Concurrent use of enzalutamide with CYP3A4 substrates that have a narrow therapeutic index should be avoided. Use of enzalutamide and any other CYP3A4 substrate should be performed with caution and close monitoring. Consider therapy modification

Ethosuximide: Amphetamines may diminish the therapeutic effect of Ethosuximide. Amphetamines may decrease the serum concentration of Ethosuximide. Monitor therapy

Gastrointestinal Acidifying Agents: May decrease the serum concentration of Amphetamines. Monitor therapy

Iobenguane I 123: Sympathomimetics may diminish the therapeutic effect of Iobenguane I 123. Avoid combination

Ioflupane I 123: Amphetamines may diminish the diagnostic effect of Ioflupane I 123. Monitor therapy

Linezolid: May enhance the hypertensive effect of Sympathomimetics. Management: Reduce initial doses of sympathomimetic agents, and closely monitor for enhanced pressor response, in patients receiving linezolid. Specific dose adjustment recommendations are not presently available. Consider therapy modification

Lithium: May diminish the stimulatory effect of Amphetamines. Monitor therapy

MAO Inhibitors: May enhance the hypertensive effect of Amphetamines. While linezolid and tedizolid may interact via this mechanism, management recommendations differ from other monoamine oxidase inhibitors. Refer to monographs specific to those agents for details. Exceptions: Linezolid; Tedizolid. Avoid combination

Methenamine: May decrease the serum concentration of Amphetamines. This effect is likely due to an enhanced excretion of amphetamines in the urine. Monitor therapy

Mitotane: May decrease the serum concentration of CYP3A4 Substrates. Management: Doses of CYP3A4 substrates may need to be adjusted substantially when used in patients being treated with mitotane. Consider therapy modification

Multivitamins/Fluoride (with ADE): May decrease the serum concentration of Amphetamines. More specifically, the ascorbic acid (vitamin C) in many multivitamins may decrease amphetamine concentrations. Monitor therapy

Multivitamins/Minerals (with ADEK, Folate, Iron): May decrease the serum concentration of Amphetamines. Monitor therapy

Multivitamins/Minerals (with AE, No Iron): May decrease the serum concentration of Amphetamines. Specifically, vitamin C may impair absorption of amphetamines. Monitor therapy

Siltuximab: May decrease the serum concentration of CYP3A4 Substrates. Monitor therapy

St John's Wort: May decrease the serum concentration of CYP3A4 Substrates. Management: Consider an alternative for one of the interacting drugs. Some combinations may be specifically contraindicated. Consult appropriate manufacturer labeling. Consider therapy modification

Sympathomimetics: May enhance the adverse/toxic effect of other Sympathomimetics. Monitor therapy

Tedizolid: May enhance the hypertensive effect of Sympathomimetics. Tedizolid may enhance the tachycardic effect of Sympathomimetics. Monitor therapy

Tocilizumab: May decrease the serum concentration of CYP3A4 Substrates. Monitor therapy

Tricyclic Antidepressants: May enhance the stimulatory effect of Amphetamines. Tricyclic Antidepressants may also potentiate the cardiovascular effects of Amphetamines. Monitor therapy

Urinary Acidifying Agents: May decrease the serum concentration of Amphetamines. Monitor therapy

Adverse Reactions

Frequency not defined.

Cardiovascular: Cardiomyopathy (with chronic amphetamine use), hypertension, ischemic heart disease (with chronic amphetamine use), palpitations, tachycardia

Central nervous system: Depression (with withdrawal), dizziness, headache, insomnia, overstimulation, psychosis (rare), restlessness

Dermatologic: Dermatological reaction, diaphoresis, urticaria

Endocrine & metabolic: Change in libido

Gastrointestinal: Diarrhea, dysgeusia, nausea, xerostomia

Neuromuscular & skeletal: Tremor

Warnings/Precautions

Concerns related to adverse effects:

• CNS effects: Amphetamines may impair the ability to engage in potentially hazardous activities (eg, driving or operating machinery).

• Primary pulmonary hypertension (PPH): A rare, frequently fatal disease of the lungs, PPH has been found to occur with increased frequency in patients receiving some anorexigens. Risk increases with therapy >3 months and repeated therapy. Patients experiencing onset/aggravation of exertional dyspnea or unexplained angina, edema (lower extremity), or syncope, should discontinue therapy immediately and be evaluated for presence of pulmonary hypertension.

• Valvular heart disease: The use of some anorexigens has been associated with the development of valvular heart disease. Risk is increased with long duration of therapy, exceeding recommended dosing, and combination use with other anorexigens. Avoid stimulants in patients with known serious structural cardiac abnormalities, cardiomyopathy, serious heart rhythm abnormalities, or other serious cardiac problems that could increase the risk of sudden death that these conditions alone carry.

Disease-related concerns:

• Diabetes: Use with caution in patients with diabetes mellitus; antidiabetic agent requirements may be altered with anorexigens and concomitant dietary restrictions.

• Hypertension: Use with caution in patients with hypertension and other cardiovascular conditions that might be exacerbated by increases in blood pressure or heart rate.

• Seizure disorders: Use with caution in patients with a history of seizure disorders.

• Tourette's syndrome: Use with caution in patients with Tourette's syndrome; stimulants may unmask tics.

Concurrent drug therapy issues:

• Anorexigens: Do not use in combination with other weight loss medications, including prescribed, over-the-counter or herbal products. Not recommended for use in patients who have used other anorectic agents within the past year.

Special populations:

• Elderly: Use caution due to risk of causing dependence, hypertension, angina, and myocardial infarction.

Other warnings/precautions:

• Abuse potential: Benzphetamine is pharmacologically related to the amphetamines, which have a high abuse potential; prolonged use may lead to dependency. Prescriptions should be written for the smallest quantity consistent with good patient care to minimize possibility of overdose.

• Discontinuation of therapy: Discontinue if satisfactory weight loss (≥4 pounds) has not occurred within the first 4 weeks of treatment, or if tolerance develops.

Monitoring Parameters

Cardiac evaluation (baseline), echocardiogram (during and after treatment), blood pressure; weight, waist circumference

Pregnancy Risk Factor

X

Pregnancy Considerations

Use is contraindicated in women who are or may become pregnant. Adverse events were observed in animal reproduction studies.

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience dry mouth, insomnia, diarrhea, nausea, agitation, tremors, sweating a lot, or bad taste. Have patient report immediately to prescriber angina, tachycardia, abnormal heartbeat, severe dizziness, passing out, mood changes, behavioral changes, severe anxiety, severe headache, decreased libido, shortness of breath, or swelling of arms or legs (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for health care professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience, and judgment in diagnosing, treating, and advising patients.

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