The pharmacology, pharmacokinetics, efficacy, and adverse effects of d
exfenfluramine hydrochloride are reviewed. Dexfenfluramine, the dextro
rotatory isomer of fenfluramine, is indicated for use in the managemen
t of obesity in patients with a body mass index of greater than or equ
al to 30 kg/m(2), or greater than or equal to 27 kg/m(2) in the presen
ce of other risk factors. Unlike fenfluramine, dexfenfluramine is a pu
re serotonin agonist. Dexfenfluramine may mimic the effect of carbohyd
rate intake. Systemic bioavailability is about 68%, and the drug is me
tabolized in the liver. In randomized, placebo-controlled trials, dexf
enfluramine was effective in reducing weight in obese patients given t
he drug for three or six months. In trials lasting one year, the stati
stically significant weight loss occurred during months 4 to 6. Dexfen
fluramine 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 controll
ing eating habits in diabetic patients, preventing weight gain after s
moking cessation, and treating bulimia, seasonal affective disorder, n
euroleptic-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 o
f the risk of serotonin syndrome. The recommended dosage is 15 mg twic
e daily. Dexfenfluramine is effective in the treatment of obesity in s
elected patients. Because its efficacy is lost after six months of con
tinuous treatment, it should be viewed primarily as an adjunct to diet
and exercise.