Green tea ingestion greatly reduces plasma concentrations of nadolol in healthy subjects

This study aimed to evaluate the effects of green tea on the pharmacokinetics and pharmacodynamics of the β-blocker nadolol. Ten healthy volunteers received a single oral dose of 30 mg nadolol with green tea or water after repeated consumption of green tea (700 ml/day) or water for 14 days. Catechin concentrations in green tea and plasma were determined. Green tea markedly decreased the maximum plasma concentration (C max) and area under the plasma concentration-time curve (AUC 0-48) of nadolol by 85.3% and 85.0%, respectively (P <0.01), without altering renal clearance of nadolol. The effects of nadolol on systolic blood pressure were significantly reduced by green tea. [ 3 H]-Nadolol uptake assays in human embryonic kidney 293 cells stably expressing the organic anion-transporting polypeptides OATP1A2 and OATP2B1 revealed that nadolol is a substrate of OATP1A2 (Michaelis constant (K m) = 84.3 μmol/l) but not of OATP2B1. Moreover, green tea significantly inhibited OATP1A2-mediated nadolol uptake (half-maximal inhibitory concentration, IC 50 = 1.36%). These results suggest that green tea reduces plasma concentrations of nadolol possibly in part by inhibition of OATP1A2-mediated uptake of nadolol in the intestine.