Benzphetamine Vs. Phentermine: Drug Comparison

Benzphetamine is a prescription medication used as a short-term aid for weight loss in people with obesity. It belongs to a class of drugs called sympathomimetic amines, which is similar to amphetamines, and works by stimulating the central nervous system to increase heart rate, blood pressure, and metabolism while also suppressing appetite. 

It is typically prescribed alongside a reduced-calorie diet and exercise plan for folks who have not been able to lose weight through lifestyle changes alone.

Due to its stimulant-like effects, benzphetamine is classified as a Schedule III controlled substance, meaning it has a potential for abuse and dependence. It should only be used only for a few weeks, as its effectiveness decreases over time, and prolonged use can lead to dependence. Because of these potential effects, benzphetamine should be used cautiously under the direction of a healthcare provider.

Phentermine is the active ingredient in brand-name medications including Adipex-P^®. The information below is about brand name Adipex-P. According to the FDA, “Generic medicines use the same active ingredients as brand-name medicines and work the same way, so they have the same risks and benefits as the brand-name medicines.”

Adipex-P (phentermine hydrochloride) is a prescription medication used as a short-term adjunct to weight loss in patients with obesity. It works as an appetite suppressant by stimulating the central nervous system, which increases heart rate and blood pressure while reducing hunger. Adipex-P is typically prescribed alongside a reduced-calorie diet and exercise regimen to enhance weight loss efforts. Common side effects include increased heart rate, dry mouth, insomnia, and nervousness. It is important to note that Adipex-P is intended for short-term use due to the potential for dependence and other adverse effects​.

Sympathomimetic amine

Sympathomimetic amine anorectic

Benzphetamine hydrochloride is indicated:

• In the management of exogenous obesity as a short term (a few weeks) adjunct in a regimen of weight reduction based on caloric restriction in patients with an initial body mass index (BMI) of 30 kg/m² or higher who have not responded to appropriate weight reducing regimen (diet and/or exercise) alone

Adipex-P (phentermine hydrochloride) is indicated:

• As a short-term adjunct (a few weeks) in a regimen of weight reduction based on exercise, behavioral modification and caloric restriction in the management of exogenous obesity for patients with an initial body mass index greater than or equal to 30 kg/m², or greater than or equal to 27 kg/m² in the presence of other risk factors (e.g., controlled hypertension, diabetes, hyperlipidemia)

• Typically taken orally one to three times daily

• Comes in 50 mg tablets

• Typically taken orally once daily

• Comes in 37.5 mg tablets

The following have been associated with the use of benzphetamine hydrochloride:

• Heart fluttering

• Fast heart beat

• Elevation of blood pressure

• Overstimulation

• Restlessness

• Dizziness

• Insomnia

• Tremor

• Sweating

• Headache

• Dryness of the mouth

• Unpleasant taste

• Nausea

• Diarrhea

• Other gastrointestinal disturbances

• Hives and other allergic reactions involving the skin

• Changes in libido

Adverse events have been reported in the following systems:

• Cardiovascular

• Central nervous system

• Gastrointestinal

• Allergic

• Endocrine

• Benzphetamine hydrochloride is contraindicated in patients with advanced arteriosclerosis, symptomatic cardiovascular disease, moderate to severe hypertension, hyperthyroidism, known hypersensitivity or idiosyncrasy to sympathomimetic amines, and glaucoma

• Benzphetamine hydrochloride should not be given to patients who are in an agitated state or who have a history of drug abuse

• Hypertensive crises have resulted when sympathomimetic amines have been used concomitantly or within 14 days following use of monoamine oxidase inhibitors

• Benzphetamine hydrochloride should not be used concomitantly with other CNS stimulants

• Benzphetamine hydrochloride may cause fetal harm when administered to a pregnant woman. If this drug is used during pregnancy, or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential hazard to the fetus

• Drug interactions: Efficacy of benzphetamine hydrochloride tablets in combination with other anorectic agents has not been studied, hypertensive crises have resulted when sympathomimetic amines have been used concomitantly or within 14 days following use of monoamine oxidase inhibitors, benzphetamine 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

• History of cardiovascular disease (e.g., coronary artery disease, stroke, arrhythmias, congestive heart failure, uncontrolled hypertension)

• During or within 14 days following the administration of monoamine oxidase inhibitors

• Hyperthyroidism

• Glaucoma

• Agitated states

• History of drug abuse

• Pregnancy

• Nursing

• Known hypersensitivity, or idiosyncrasy to the sympathomimetic amines

• Drug interactions: Monoamine oxidase inhibitors, alcohol, insulin and oral hypoglycemics, adrenergic neuron blocking drugs

• 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

• 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

• Benzphetamine hydrochloride should not be used in combination with other anorectic agents, including prescribed drugs, over-the-counter preparations and herbal products

• In a case-control epidemiological study, the use of anorectic agents was associated with an increased risk of developing pulmonary hypertension, a rare, but often fatal disorder

• The onset or aggravation of exertional dyspnea, or unexplained symptoms of angina pectoris, syncope, or lower extremity edema suggest the possibility of occurrence of pulmonary hypertension

• Valvular heart disease associated with the use of some anorectic agents such as fenfluramine and dexfenfluramine has been reported

• The potential risk of possible serious adverse effects such as valvular heart disease and pulmonary hypertension should be assessed carefully against the potential benefit of weight loss

• 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

• Benzphetamine hydrochloride is not recommended for severely hypertensive patients or for patients with symptomatic cardiovascular disease including arrhythmias

• Benzphetamine hydrochloride is not recommended for patients who used any anorectic agents within the prior year

• Pregnancy: Benzphetamine hydrochloride is contraindicated in pregnancy

• Breastfeeding: Mothers taking amphetamines should be advised to refrain from nursing

• Coadministration with other drugs for weight loss is not recommended

• Rare cases of primary pulmonary hypertension have been reported

• Rare cases of serious regurgitant cardiac valvular disease have been reported

• Tolerance to the anorectic effect usually develops within a few weeks

• Adipex-P may impair the ability of the patient to engage in potentially hazardous activities such as operating machinery or driving a motor vehicle

• Risk of abuse and dependence

• Concomitant alcohol use may result in an adverse drug reaction

• Use caution in patients with even mild high blood pressure

• A reduction in dose of insulin or oral hypoglycemic medication may be required in some patients

• Breastfeeding: Discontinue drug or nursing taking into consideration importance of drug to mother

*This information is from the benzphetamine hydrochloride label used by Epic Pharma, LLC. See the Full Prescribing Information for more complete information. Benzphetamine hydrochloride may also be the active ingredient in other medications, and this information may not be accurate for all medications that include the active ingredient benzphetamine hydrochloride.

*This information is from the label for brand name Adipex-P^®. See the Full Prescribing Information for more complete information. Phentermine, the active ingredient in Adipex-P, may also be the active ingredient in other medications, and this information may not be accurate for all medications that include the active ingredient phentermine.