Induction of Obesity by Psychotropic Drugs

Evidence from published studies and clinical experience indicates that neuroleptic drugs, tricyclic and heterocyclic antidepressants, monoamine oxidase inhibitor antidepressants, and lithium all possess varying abilities to increase appetite, stimulate carbohydrate craving, and cause weight gain over prolonged periods of administration. Sedatives and benzodiazepine-type antianxiety drugs fail to stimulate appetite or induce weight gain, and it is unlikely that the sedative or calming effects of other psychotropic drugs contribute significantly to changes in appetite or weight. Studies of the endocrine and metabolic aspects of psychotropic drugs suggest that these mechanisms do not contribute significantly to explaining the observed effects on appetite or weight. Numerous studies indicate that a wide variety of compounds, including the serotonin precursor, tryptophan, the serotonin receptor stimulant, fenfluramine, and the serotonin reuptake inhibitor, fluoxetine, are all capable of decreasing carbohydrate hunger, reducing consumption of carbohydrate-rich foods, and inhibiting weight gain in humans and animals. Widely divergent psychotropic drugs produce antagonistic effects at serotonin receptor sites, and it is likely that this action contributes to their ability to stimulate appetite, carbohydrate craving, and weight gain. Those psychotropic drugs that inhibit serotonin reuptake mechanisms, increasing serotonin activity within the central nervous system, either fail to stimulate carbohydrate hunger and weight gain or are actually capable of decreasing carbohydrate craving and facilitating weight loss. Because many antidepressants, including trazodone and amitriptyline, the neuroleptic, chlorpromazine, and the mood stabilizer, lithium, may all, under some circumstances, inhibit serotonin reuptake mechanisms and may simultaneously block serotonin receptor sites, their effects on appetite and weight gain may represent a balance between serotonergic and antiserotonin activities. Monoamine oxidase inhibitors, which slow the metabolic degradation of monoamines, including serotonin and norepinephrine, allow for increased levels of these neurotransmitters within the brain. It is conceivable that the relative noradrenergic effect related to an amphetamine-like structure of tranylcypromine may explain its lesser ability to stimulate appetite and weight gain than the appetite and weight effects observed with phenelzine. Furthermore, the production of dry mouth and thirst by psychotropic drugs appears to contribute to weight gain, secondary to consumption of high-calorie beverages.(ABSTRACT TRUNCATED AT 400 WORDS)