Stimulant drugs commonly abused in the USA include methamphetamine (“crank,” “crystal”), methylenedioxymethamphetamine (MDMA, “ecstasy”), and cocaine (“crack”) as well as pharmaceuticals such as pseudoephedrine (Sudafed) and ephedrine (as such and in the herbal agent Ma-huang) (see Chapter 32). Caffeine is often added to dietary supplements sold as “metabolic enhancers” or “fat burners.” Newer synthetic analogs of amphetamines (often sold on the street as “bath salts”) and synthetic agonists of the endogenous cannabinoid receptors (sold as “research chemicals” or “spice”) are becoming popular drugs of abuse.
At the doses usually used by stimulant abusers, euphoria and wakefulness are accompanied by a sense of power and well-being. At higher doses, restlessness, agitation, and acute psychosis may occur, accompanied by hypertension and tachycardia. Prolonged muscular hyperactivity or seizures may contribute to hyperthermia and rhabdomyolysis. Body temperatures as high as 42°C (107.6°F) have been recorded. Hyperthermia can cause brain damage, hypotension, coagulopathy, and renal failure.
Treatment for stimulant toxicity includes general supportive measures as outlined earlier. There is no specific antidote. Seizures and hyperthermia are the most dangerous manifestations and must be treated aggressively. Seizures are usually managed with intravenous benzodiazepines (eg, lorazepam). Temperature is reduced by removing clothing, spraying with tepid water, and encouraging evaporative cooling with fanning. For very high body temperatures (eg, >40–41°C [104–105.8°F]), neuromuscular paralysis (eg, with vecuronium) is used to abolish muscle activity quickly.
A large number of prescription and nonprescription drugs, as well as a variety of plants and mushrooms, can inhibit the effects of acetylcholine at muscarinic receptors. Some drugs used for other purposes (eg, antihistamines) also have anticholinergic effects, in addition to other potentially toxic actions. For example, antihistamines such as diphenhydramine can cause seizures; tricyclic antidepressants, which have anticholinergic, quinidine-like, and α-blocking effects, can cause severe cardiovascular toxicity.
The classic anticholinergic (technically, “antimuscarinic”) syndrome is remembered as “red as a beet” (skin flushed), “hot as a hare” (hyperthermia), “dry as a bone” (dry mucous membranes, no sweating), “blind as a bat” (blurred vision, cycloplegia), and “mad as a hatter” (confusion, delirium). Patients usually have sinus tachycardia, and the pupils are usually dilated (see Chapter 8). Agitated delirium or coma may be present. Muscle twitching is common, but seizures are unusual unless the patient has ingested an antihistamine or a tricyclic antidepressant. Urinary retention is common, especially in older men.