Metabolic activation and cytotoxicity of carvedilol mediated by cytochrome P450s in vitro and in vivo.

Carvedilol (CAR) is commonly administered in the treatment of essential hypertension. Current reports suggest that CAR therapy may elevate the risk of hepatotoxicity, occasionally progressing to liver injury. However, the underlying mechanisms of the toxicity remain poor understood. This study investigated CAR-associated hepatotoxicity through reactive metabolites formation. In the microsomal incubation mixture containing CAR (50 μM), four phase I metabolites (M1-M4) were detected. Upon the addition of glutathione (GSH), N-acetylcysteine (NAC), or cysteine as trapping agents, four GSH conjugates (M5-M8), four NAC conjugates (M9-M12), and four cysteine conjugates (M13-M16) were also detected. Chemical synthesis of 8-hydroxy CAR identified M1 as the primary oxidative metabolite of CAR. Following the administration of CAR (25 mg/kg), we detected GSH conjugate (M5) in bile, NAC conjugate (M9) in urine, and cysteine adduct (M13) in proteolytic mixture of liver tissues of rat. Furthermore, it was found that CYP3A4 dominated the metabolic activation of CAR. Additionally, CAR exhibited time-course changes and dose-dependent (0, 25, 50, and 100 mg/kg) protein adduction in rat liver tissues, as well as time- and concentration-dependent (0, 10, 25, 50 and 100 μM) inhibition of hepatocyte viability. Ketoconazole (KTZ) significantly decreased the susceptibility of hepatocytes to CAR-induced cytotoxicity. Collectively, these findings offer new insight into the hepatotoxicity mechanism associated with the metabolic activation of CAR.