Of the two isomers of amphetamine, dextroamphetamine appears to have greater CNS stimulation. These actions produce respiratory stimulation, a pressor response, mydriasis, bronchodilation, and contraction of the bladder sphincter. The effect of amphetamines on GI tract motility is unpredictable. In treating children with attention-deficit hyperactivity disorder, amphetamines produce a calming effect. This action of amphetamines results in a decrease in hyperactivity and an increase in the child's attention span.
Amphetamines seem to exert an anorexogenic effect.
As a result of these effects, weight decreases. This agent is useful as an adjunct to decreased caloric intake in the treatment of obesity. The anorexogenic effect is postulated to be secondary to CNS stimulation and a decrease in the acuity of smell and taste. Amphetamines do not seem to alter the basal metabolic rate or nitrogen excretion. Metabolism occurs in the liver.