Blood pressure and plasma norepinephrine responses to dexfenfluramine in obese postmenopausal women.

Dexfenfluramine has been shown to reduce body weight and lower blood pressure in obese individuals. However. it is not clear whether the blood pressure-lowering effect is due to dexfenfluramine or to the loss of weight. This project was designed to study the effect of a 5-d treatment of dexfenfluramine on blood pressure changes in obese postmenopausal women. Twenty women aged 51-60 y matched for body mass index [BMI (in kg/m2) of 34.5-50.1] were assigned to either the dexfenfluramine group (15 mg orally twice a day for 5 d) or the control group. All subjects were instructed about an isoenergetic diet. Twenty-four-hour ambulatory blood pressure, plasma catecholamines, glucose, insulin, and lipids were measured at the beginning and repeated at the conclusion of the study. On day 5 the mean systolic (SBP) and mean diastolic blood pressures (DBP) in the dexfenfluramine group were lower than those of the control group (SBP: 114+/-7 mm Hg in the dexfenfluramine group compared with 124+/-12 mm Hg in the control group, P < 0.05; DBP: 70+/-9 mm Hg in the dexfenfluramine group compared with 76+/-10 mm Hg in the control group, P < 0.05). The mean plasma norepinephrine concentration was lower in the dexfenfluramine group than in the control group (1.60+/-0.5 compared with 2.41+/-0.5 nmol/L, respectively, P < 0.05). No differences were noted in epinephrine, glucose, insulin. and lipid concentrations between the two groups. We showed that a 5-d treatment of dexfenfluramine decreases blood pressure and reduces heart rate in obese postmenopausal women. Our data suggest that these effects are results of the direct action of dexfenfluramine.