Epigallocatechin gallate (EGCG), irreversibly inhibits cytochrome P450 (CYP) 3A subfamily and P-glycoprotein (P-gp) in vitro. This study investigated the effect of oral EGCG on the pharmacokinetics of intravenous and oral nicardipine in rats. Nicardipine was administered orally (12 mg/kg) or intravenously (4 mg/kg) with or without oral EGCG (0.5, 3 or 10 mg/kg) to rats. Compared to controls (without EGCG), the total areas under the plasma concentration- time curve (AUCs) of intravenous nicardipine were greater with oral EGCG. Compared to controls (without EGCG), the AUCs of oral nicardipine and the extent of absolute oral bio-availability (F) were also greater with oral EGCG. The above data suggest that oral EGCG inhibited both the hepatic CYP3A subfamily and intestinal P-gp.