BENZPHETAMINE HYDROCHLORIDE
(benz-fet'a-meen)
Didrex
Classifications: central nervous system agent; cerebral stimulant; anorexiant
Prototype: Amphetamine
Pregnancy Category: X
Controlled Substance: Schedule III

Availability

25 mg, 50 mg tablets

Actions

Indirect acting sympathomimetic amine with amphetamine-like actions but with fewer side effects than amphetamine.

Therapeutic Effects

Anorexiant effect thought to be secondary to stimulation of hypothalamus to release stored catecholamines in the CNS.

Uses

Short-term adjunct in management of exogenous obesity.

Contraindications

Known hypersensitivity to sympathomimetic amines; angle-closure glaucoma; advanced arteriosclerosis, angina pectoris, severe cardiovascular disease, moderate to severe hypertension; hyperthyroidism, agitated states; history of drug abuse; children <12 y; lactation. Safe use during pregnancy (category X) is not established.

Cautious Use

Diabetes mellitus; older adults; psychosis.

Route & Dosage

Obesity
Adult: PO 25–50 mg 1–3 times/d

Administration

Oral

Give as a single daily dose, preferably midmorning or midafternoon, according to patient's eating habits.
Schedule daily dose no later than 6 h before patient retires to avoid insomnia.
Store in tight, light-resistant containers at 15°–30° C (59°–86° F) unless otherwise directed.

Adverse Effects (1%)

CNS: Euphoria, irritability, hyperactivity, nervousness, restlessness, insomnia, tremor, headache, light-headedness, dizziness, depression following stimulant effects. CV: Palpitation, tachycardia, elevated BP, irregular heart beat. GI: Xerostomia, nausea, vomiting, diarrhea or constipation, abdominal cramps. Chronic Intoxication: Marked insomnia, irritability, hyperactivity, personality changes, psychosis, severe dermatoses.

Interactions

Drug: Acetazolamide, sodium bicarbonate decrease amphetamine elimination; ammonium chloride, ascorbic acid increase amphetamine elimination; barbiturates may antagonize the effects of both drugs; furazolidone may increase BP effects of amphetamines, and interaction may persist for several weeks after discontinuation of furazolidone; guanethidine, guanadryl antagonize antihypertensive effects; because mao inhibitors, selegiline can cause hypertensive crisis (fatalities reported); do not administer amphetamines during or within 14 d of these drugs; phenothiazines may inhibit mood-elevating effects of amphetamines; tricyclic antidepressants enhance amphetamine effects because they increase norepinephrine release; beta agonists increase amphetamine's adverse cardiovascular effects.

Pharmacokinetics

Absorption: Readily absorbed from GI tract. Duration: 4 h. Elimination: Renal elimination.

Nursing Implications

Assessment & Drug Effects

Assess for signs of excessive CNS stimulation: insomnia, restlessness, tremor, palpitations. These may indicate need for dosage adjustment.
Monitor vital signs; report elevated BP, tachycardia, and irregular heart rhythm.
Monitor diabetics for loss of glycemic control.

Patient & Family Education

Note: Anorexiant effects are temporary and tolerance may occur; long-term use is not indicated.
Do not drive or engage in potentially hazardous activities until response to drug is known.
Do not terminate high dosage therapy abruptly; GI distress, stomach cramps, trembling, unusual tiredness, weakness, and mental depression may result.
Do not breast feed while taking this drug.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug