['The serotonin and norepinephrine transporter inhibitor sibutramine is a widely used antiobesity drug. In acute studies, the peripheral sympathomimetic effect of sibutramine was counteracted by a central sympatholytic action.', 'The objective was to test the hypothesis that blood pressure responses to long-term sibutramine therapy may be related to sympathetic nerve traffic before treatment in a prospective open-label study in an academic clinical research center.', 'This study comprised 20 obese subjects (body mass index, 30-40 kg/m2; age, 30-57 yr) receiving 5 d of placebo treatment followed by open-label 15 mg/d sibutramine and hypocaloric diet over 12 wk.', 'Body weight, blood pressure, heart rate, muscle sympathetic nerve activity (MSNA) (microneurography), plasma catecholamines, and adipose tissue gene expression were measured.', 'Open-label sibutramine treatment decreased body weight 4.1 kg (P<0.01) and MSNA 17 bursts per minute (P=0.001), and increased diastolic blood pressure 3 mm Hg (P<0.05) and heart rate 8 bpm (P<0.01). The change in blood pressure with sibutramine treatment was inversely correlated with initial MSNA (r2=0.34; P<0.01). Chronic sibutramine treatment increased adrenoreceptor gene expression and plasma catecholamines.'] Does sympathetic vasomotor tone determine blood pressure response to long-term sibutramine treatment?