Dexfenfluramine hydrochloride: an anorexigenic agent.

The pharmacology, pharmacokinetics, efficacy, and adverse effects of dexfenfluramine hydrochloride are reviewed. Dexfenfluramine, the dextrorotatory isomer of fenfluramine, is indicated for use in the management of obesity in patients with a body mass index of > or = 30 kg/m2, or > or = 27 kg/m2 in the presence of other risk factors. Unlike fenfluramine, dexfenfluramine is a pure serotonin agonist. Dexfenfluramine may mimic the effect of carbohydrate intake. Systemic bioavailability is about 68%, and the drug is metabolized in the liver. In randomized, placebo-controlled trials, dexfenfluramine was effective in reducing weight in obese patients given the drug for three or six months. In trials lasting one year, the statistically significant weight loss occurred during months 4 to 6. Dexfenfluramine reduces blood pressure, percent glycosylated hemoglobin, and concentrations of blood glucose and blood lipids, but these benefits may be indirect. Dexfenfluramine may also be of some value in controlling eating habits in diabetic patients, preventing weight gain after smoking cessation, and treating bulimia, seasonal affective disorder, neuroleptic-induced obesity, and premenstrual syndrome. Dexfenfluramine's most frequent adverse effects are insomnia, diarrhea, and headache; it has also been associated with primary pulmonary hypertension. The drug should not be combined with other serotonergic agonists because of the risk of serotonin syndrome. The recommended dosage is 15 mg twice daily. Dexfenfluramine is effective in the treatment of obesity in selected patients. Because its efficacy is lost after six months of continuous treatment, it should be viewed primarily as an adjunct to diet and exercise.