Sympathetic vasomotor tone determines blood pressure response to long-term sibutramine treatment.

CONTEXT

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.

OBJECTIVE

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.

PATIENTS

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.

MAIN OUTCOME MEASURES

Body weight, blood pressure, heart rate, muscle sympathetic nerve activity (MSNA) (microneurography), plasma catecholamines, and adipose tissue gene expression were measured.

RESULTS

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.

CONCLUSIONS

The blood pressure response to sibutramine treatment is related to initial MSNA so that subjects with higher MSNA exhibit a smaller increase or even a decrease in blood pressure. The phenomenon might be explained by a sustained reduction in central sympathetic activity with sibutramine treatment.