Pharmacokinetics of vigabatrin: implications of creatinine clearance

The pharmacokinetics of both enantiomers of vigabatrin after a single oral dose in healthy young subjects (mean creatinine clearance 120 ml/min) were compared with kinetics in two groups of elderly subjects, one group aged 60 to 75 years (mean creatinine clearance 86 ml/min) and one group aged 76 to 97 years (mean creatinine clearance 30 ml/min). At a dose of 1500 mg, the group with the eldest subjects and the lowest creatinine clearance values showed mean increases of 3.3-fold in the time to reach the maximum concentration, 2.7-fold in the maximum concentration, and 9.8-fold in the AUC; a twofold prolongation of the t1/2; and reduced urinary excretion of the biologically and pharmacologically active S(+)-enantiomer. Changes in the intermediate group were qualitatively similar but quantitatively less. Parallel observations were made for the inactive R(-)-enantiomer. Most of these changes can be related to decreased renal clearance of vigabatrin. No interference of either enantiomer in the renal clearance of the other was noted. A nonlinear relationship between renal clearance and creatinine clearance for both enantiomers is suggested. Knowledge of the patient's renal function and an appropriate dose adjustment will minimize side effects during vigabatrin therapy, especially in elderly patients.