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.