Enantioselective disposition of clenbuterol in rats

摘要: Clenbuterol is a long-acting β2-adrenoceptor agonist and bronchodilator that used for the treatment of asthma, but desired activities reside almost exclusively in (-)-R-enantiomer. This study examined enantioselectivity disposition clenbuterol following administration racemate to rats. Concentrations enantiomers plasma, urine bile were determined by LC-MS/MS assay with Chirobiotic T column. method was confirmed show high sensitivity, specificity precision, 0.1 ml volumes plasma precisely quantified at concentrations as low 0.25 ng/ml. The pharmacokinetic profiles intravenous intraduodenal (2 mg/kg) rats significantly different. distribution volume (-)-R-clenbuterol (9.17 l/kg) higher than (+)-S-clenbuterol (4.14 l/kg). total body clearance (13.5 ml/min/kg) (+)-S-enantiomer (11.5 ml/min/kg). An situ absorption jejunal loops showed no difference residual amount between (-)-R- (+)-S-enantiomers. Urinary same two enantiomers, biliary excretion (+)-S-enantiomer. fractions free (non-protein-bound) rat 48.8% 33.1%, respectively. These results indicated there are differences these may be predominantly due enantioselective protein binding.