P-glycoprotein interactions of nefazodone and trazodone in cell culture

This study investigated the effects of nefazodone (NFZ) and trazodone (TZD) on P-glycoprotein (P-gp) activity and expression in cell culture. NFZ and TZD showed no differential transport between the basolateral to apical and apical to basolateral direction across Caco-2 cell monolayers. Transport in either direction was not affected by verapamil. NFZ was a potent inhibitor (IC50 = 4.7 muM) of rhodamine123 (Rh 123)B to A transport across Caco-2 ce ll monolayers, while TZD had minimal effect. Following 72-hour exposure of LS180V cells to NFZ and TZD (10 muM), a twofold increase in immunoreactive P-gp was observed. Rh123 accumulation into these cells was reduced to 65% a nd 74% of control by NFZ and TZD (1 a muM), respectively. It was concluded that differential rates of transport of NFZ and TZD in Caco-2 cells were no t evident. However, NFZ is an inhibitor of P-gp activity at clinically rele vant in vivo concentrations and may have the potential to increase bioavail ability of coadministered compounds that are substrates far transport. Conc entrations of NFZ and TZD achieved in the intestine after chronic oral dosi ng may induce P-gp expression and reduce absorption of coadministered drugs .