special subjects
Amphetamines
Pathophysiology
Amphetamines enhance release of catecholamines, increasing intrasynaptic levels ofnorepinephrine,dopamine, and serotonin. The resulting marked alpha- and beta-receptor stimulation and general central nervous system excitation account for the “desired” effects of increased alertness, euphoria, and anorexia, as well as the adverse effects of delirium, hypertension, hyperthermia, and seizures. Effects of amphetamines are similar, varying in intensity and duration of psychoactive effects; MDMA and its relatives have more mood-enhancing properties, perhaps related to a greater effect on serotonin. Amphetamines can be taken orally as pills or capsules, nasally by inhaling or smoking, or by injection. Repeated use of amphetamines induces dependence. Tolerance develops slowly, but amounts several 100-fold greater than the amount originally used may eventually be ingested or injected. Tolerance to various effects develops unequally. Tachycardia and increased alertness diminish, but hallucinations and delusions may occur. Amphetamines typically cause Erectile Dysfunction in men but enhance sexual desire. Use is associated with unsafe sex practices, and users are at increased risk of Necrotizing vasculitis that involves multiple organ systems can occur. Use of certainamphetamine-related appetite suppressants (dexfenfluramine,fenfluramine,phentermine) has been associated with valvular heart disease. Dexfenfluramine andfenfluraminewere removed from the US market in 1997.Phentermine-fenfluramine(Phen-fen) products were similarly withdrawn from the US market, butphenterminealone and in combination withtopiramateis available as an anorectic. 