Carvedilol is often used to treat hypertension and for prophylaxis in vascular sclerosis in renal transplant recipients, who require concomitant treatment with ciclosporin. However, there are few reports regarding the pharmacokinetic interactions between carvedilol and ciclosporin. We have investigated the potential effects of carvedilol on the pharmacokinetics of ciclosporin, and examined the inhibitory effects of carvedilol on P-glycoprotein-mediated transcellular transport using Caco2 cells. Ciclosporin alone or with carvedilol was orally or intravenously administered to rats. The oral administration of carvedilol (10 mg kg(-1)) with ciclosporin (10 mg kg(-1)) increased the whole blood concentration of ciclosporin. When ciclosporin (3 mg kg(-1)) was intravenously administered with carvedilol (3 mg kg(-1)), there was no difference in the whole blood ciclosporin concentration between administration with and without carvedilol. Co-administration with carvedilol increased ciclosporin bioavailability from 33% to 70%. In Caco2 cells, carvedilol caused a concentration-dependent increase in the intracellular accumulation of ciclosporin, and its effect was comparable with that of verapamil. Carvedilol considerably raised the concentration of ciclosporin in the blood and this interaction was associated with the absorption phase of ciclosporin. This interaction was caused by the inhibition of P-glycoprotein-mediated transport by carvedilol in the intestine.
Cyclosporine (CSA), which is one of the substrates of ATP binding cassette subfamily B member 1 (ABCB1), is widely used as an immunosuppressant in patients undergoing transplantation. The expression level of P-glycoprotein on lymphocytes that is encoded by ABCB1 gene is considered to be one of the major causes of differences in intracellular CSA concentration. The clinical relevance of ABCB1 mRNA expression in peripheral blood was analyzed. We examined (i) the relationship between ABCB1 mRNA and the intracellular concentration of CSA in vitro, (ii) the change in long-term ABCB1 mRNA expression levels, and (iii) its association with acute rejection (AR) or cytomegalovirus (CMV) reactivation in living-donor renal transplantation. A significantly negative correlation between ABCB1 mRNA expression and intracellular CSA concentration in vitro was obtained (p<0.05). ABCB1 mRNA expression was significantly reduced (55%) 1 week after transplantation (p<0.001) and returned to the pre-transplantation level after 1 year. Although the sample size may be too small to obtain a definitive conclusion, no association was observed between ABCB1 mRNA expression levels and AR or CMV reactivation. Key words ATP binding cassette subfamily B member 1 (ABCB1); mRNA; renal transplantation; cyclosporine A P-Glycoprotein (P-gp) is encoded by the ATP binding cassette subfamily B member 1 (ABCB1, also known as multidrug resistance protein 1 (MDR1)) gene. This membrane protein functions as an energy-dependent drug efflux pump and reduces the intracellular concentrations of a wide range of drugs. P-gp was first identified as a surface phosphoglycoprotein expressed in drug resistant tumor cells, and its expression has been correlated with failed chemotherapeutic treatment and poor prognosis.
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