Clinical evidence,mechanism, importance and management
In a single-dose study in 12 healthy subjects, tolcapone 200mg had no effect on pharmacokinetics of tolbutamide 500 mg, and did not alter glucose-lowering effect of tolbutamide (See reference number 1). This study was conducted since in vitro evidence showed that tolcapone inhibits cytochrome P450 isoenzyme CYP2C9, by which tolbutamide is metabolised. However, findings in healthy subjects suggest that no clinically relevant changes in pharmacokinetics of tolbutamide are likely.
1. Jorga KM,Fotteler B, Gasser R, Banken L, Birnboeck H. Lack of interaction between tolcapone and tolbutamide in healthy volunteers. J Clin Pharmacol (2000) 40, 544–51.