indication

For the management of exogenous obesity as a short term adjunct (a few weeks) in a regimen of weight reduction based on caloric restriction

pharmacology

Benzphetamine, a phenylalkylamin, is related to amphetamine both chemically and pharmacologically. It is an anorectic agent indicated in the management of exogenous obesity as a short term adjunct (a few weeks) in a regimen of weight reduction based on caloric restriction. Benzphetamine is a sympathomimetic amine with pharmacologic activity similar to the prototype drugs of this class used in obesity, the amphetamines. Actions 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.

mechanism of action

Although the mechanism of action of the sympathomimetic appetite suppressants in the treatment of obesity is not fully known, these medications have pharmacological effects similar to those of amphetamines. Amphetamine and related sympathomimetic medications (such as benzphetamine) are thought to stimulate the release of norepinephrine and/or dopamine from storage sites in nerve terminals in the lateral hypothalamic feeding center, thereby producing a decrease in appetite. This release is mediated by the binding of benzphetamine to centrally located adrenergic receptors.

toxicity

LD₅₀=160 mg/kg (orally in rats). Acute overdosage may result in restlessness, tremor, tachypnea, confusion, assaultiveness, and panic states.

biotransformation

Hepatic. Benzphetamine's metabolites include amphetamine and methamphetamine.

absorption

Readily absorbed from the gastro-intestinal tract and buccal mucosa. It Is resistant to metabolism by monoamine oxidase.

half life

16 to 31 hours

drug interactions

Chlorpromazine: Antipsychotics may diminish the stimulatory effect of Amphetamines. Monitor effectiveness of amphetamine therapy when altering concurrent antipsychotic therapy as antipsychotic agents may impair the stimulatory effect of amphetamines.

Fluoxetine: Amphetamines may enhance the adverse/toxic effect of Serotonin Modulators. The risk of serotonin syndrome may be increased. Monitor patients closely for signs and symptoms of serotonin syndrome (e.g., agitation, tremor, tachycardia, etc.) when using amphetamines and serotonin modulators in combination.

Fluphenazine: Antipsychotics may diminish the stimulatory effect of Amphetamines. Monitor effectiveness of amphetamine therapy when altering concurrent antipsychotic therapy as antipsychotic agents may impair the stimulatory effect of amphetamines.

Fluvoxamine: Amphetamines may enhance the adverse/toxic effect of Serotonin Modulators. The risk of serotonin syndrome may be increased. Monitor patients closely for signs and symptoms of serotonin syndrome (e.g., agitation, tremor, tachycardia, etc.) when using amphetamines and serotonin modulators in combination.

Guanethidine: Benzphetamine may decrease the effect of guanethidine.

Isocarboxazid: MAO Inhibitors may enhance the hypertensive effect of Amphetamines. Concomitant use of amphetamines and monoamine oxidase inhibitors (MAOI) should be avoided. If used concomitantly, careful monitoring of blood pressure must occur. It may take up to 2 weeks after the discontinuation of an MAOI for the effects to dissipate enough to afford safety to the administration of interacting agents.

Mesoridazine: Antipsychotics may diminish the stimulatory effect of Amphetamines. Monitor effectiveness of amphetamine therapy when altering concurrent antipsychotic therapy as antipsychotic agents may impair the stimulatory effect of amphetamines.

Methotrimeprazine: Antipsychotics may diminish the stimulatory effect of Amphetamines. Monitor effectiveness of amphetamine therapy when altering concurrent antipsychotic therapy as antipsychotic agents may impair the stimulatory effect of amphetamines.

Paroxetine: Amphetamines may enhance the adverse/toxic effect of Serotonin Modulators. The risk of serotonin syndrome may be increased. Monitor patients closely for signs and symptoms of serotonin syndrome (e.g., agitation, tremor, tachycardia, etc.) when using amphetamines and serotonin modulators in combination.

Perphenazine: Antipsychotics may diminish the stimulatory effect of Amphetamines. Monitor effectiveness of amphetamine therapy when altering concurrent antipsychotic therapy as antipsychotic agents may impair the stimulatory effect of amphetamines.

Phenelzine: MAO Inhibitors may enhance the hypertensive effect of Amphetamines. Concomitant use of amphetamines and monoamine oxidase inhibitors (MAOI) should be avoided. If used concomitantly, careful monitoring of blood pressure must occur. It may take up to 2 weeks after the discontinuation of an MAOI for the effects to dissipate enough to afford safety to the administration of interacting agents.

Prochlorperazine: Antipsychotics may diminish the stimulatory effect of Amphetamines. Monitor effectiveness of amphetamine therapy when altering concurrent antipsychotic therapy as antipsychotic agents may impair the stimulatory effect of amphetamines.

Promethazine: Antipsychotics may diminish the stimulatory effect of Amphetamines. Monitor effectiveness of amphetamine therapy when altering concurrent antipsychotic therapy as antipsychotic agents may impair the stimulatory effect of amphetamines.

Propericiazine: Antipsychotics may diminish the stimulatory effect of Amphetamines. Monitor effectiveness of amphetamine therapy when altering concurrent antipsychotic therapy as antipsychotic agents may impair the stimulatory effect of amphetamines.

Rasagiline: MAO Inhibitors may enhance the hypertensive effect of Amphetamines. Concomitant use of amphetamines and monoamine oxidase inhibitors (MAOI) should be avoided. If used concomitantly, careful monitoring of blood pressure must occur. It may take up to 2 weeks after the discontinuation of an MAOI for the effects to dissipate enough to afford safety to the administration of interacting agents.

Sodium bicarbonate: Alkalinizing agents such as sodium bicarbonate may decrease the excretion of amphetamines like benzphetamine. Increased clinical effects and/or toxicity may occur. Therapy modification should be considered.

Telithromycin: Telithromycin may reduce clearance of Benzphetamine. Consider alternate therapy or monitor for changes in the therapeutic/adverse effects of Benzphetamine if Telithromycin is initiated, discontinued or dose changed.

Thioridazine: Antipsychotics may diminish the stimulatory effect of Amphetamines. Monitor effectiveness of amphetamine therapy when altering concurrent antipsychotic therapy as antipsychotic agents may impair the stimulatory effect of amphetamines.

Tramadol: Increased risk of serotonin syndrome. Monitor for symptoms of serotonin syndrome.

Trandolapril: Benzphetamine may reduce the efficacy of Trandolapril.

Tranylcypromine: The MAO inhibitor, Tranylcypromine, may increase the vasopressor effect of the amphetamine, Benzphetamine. Concomitant therapy should be avoided.

Trifluoperazine: Antipsychotics may diminish the stimulatory effect of Amphetamines. Monitor effectiveness of amphetamine therapy when altering concurrent antipsychotic therapy as antipsychotic agents may impair the stimulatory effect of amphetamines.

Triprolidine: Triprolidine may reduce the sedative effect of the antihistamine, Benzphetamine.

Voriconazole: Voriconazole, a strong CYP3A4 inhibitor, may increase the serum concentration of benzphetamine by decreasing its metabolism. Monitor for changes in the therapeutic and adverse effects of benzphetamine if voriconazole is initiated, discontinued or dose changed.