Pharmacokinetics of sabeluzole and dextromethorphan oxidation capacity in patients with severe hepatic dysfunction and healthy volunteers

Aims The primary objective of this study was to determine how the pharmacok inetics of sabeluzole, an investigational drug with specific effects on mem ory and learning abilities, are affected by chronic liver disease. Since sa beluzole is metabolised by CYP2D6, a secondary objective was to study the c orrelation between CYP2D6 activity (as assessed by the dextromethorphan dex trorphan metabolic ratio) and hepatic dysfunction. Methods The single-dose pharmacokinetics of sabeluzole (10 mg) was compared in 10 healthy Caucasian subjects and 10 patients with severe hepatic dysfu nction. The urinary dextromethorphan/dextrorphan (DMP/DRP) metabolic ratio was determined after intake of 20 mg dextromethorphan (NODEX(R) capsules). Results The terminal half-life of sabeluzole was significantly prolonged in subjects with severe hepatic dysfunction vs healthy subjects (respectively 39.3 +/- 11.5 h; 17.5 +/- 10.2 h (mean +/- s.d.)). The areas under the cur ve (AUC) were significantly higher in subjects with severe hepatic dysfunct ion than in healthy volunteers (681 +/- 200 ng ml(-1)h vs 331 +/- 282 ng ml (-1)h). There was a significant correlation between the AUC(0,infinity) and the DMP/DRP metabolic ratio in healthy volunteers and subjects with severe hepatic dysfunction. AUC was greater and elimination of sabeluzole slower in poor metabolizers compared with extensive metabolizers. Conclusions These results suggest that a) sabeluzole dose should be reduced in patients with severe hepatic dysfunction and b) the AUC of sabeluzole i s linked to individual CYP2D6 activity.