Sibutramine pharmacokinetics in young and elderly healthy subjects

Objective: To investigate the pharmacokinetics of the pharmacologically active metabolites of sibutramine (metabolites 1 and 2) in healthy young and elderly volunteers following a single oral dose of sibutramine. Methods: This was an open, parallel-group study completed by 12 young (six male, six female; mean age 24.0 years) and 12 elderly (six male, six female, mean age 70.3 years) healthy volunteers. Blood samples were taken at intervals up to 48 h post-dose. Plasma concentrations of metabolites were determined using HPLC-MS. Model-independent pharmacokinetic parameters of the two metabolites were compared for the two age groups. Results: The similarity of the plasma profiles of the two desmethyl metabolites showed that despite the possibility of reduced hepatic function due to age, the rate and extent of formation of these was the same in both young and elderly, i.e. sibutramine metabolism was not impaired in elderly subjects. There were also no significant differences in elimination of metabolite 2 between groups, although the elderly group showed a slight trend for a reduction in k(el). Conclusions: The pharmacokinetics of the two pharmacologically active metabolites of sibutramine (metabolites 1 and 2) were not significantly different between the young and elderly groups in this study. Based on this information, a similar dosing regimen would be appropriate for both the young and elderly.