RT Journal Article
SR Electronic
T1 Quantitative Prediction of Metabolic Inhibition of Midazolam by Erythromycin, Diltiazem, and Verapamil in Rats: Implication of Concentrative Uptake of Inhibitors into Liver
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 1118
OP 1126
VO 292
IS 3
A1 Yamano, Katsuhiro
A1 Yamamoto, Koujirou
A1 Kotaki, Hajime
A1 Takedomi, Sayuri
A1 Matsuo, Hirotami
A1 Sawada, Yasufumi
A1 Iga, Tatsuji
YR 2000
UL http://jpet.aspetjournals.org/content/292/3/1118.abstract
AB To evaluate the degree of drug-drug interaction concerning metabolic inhibition in the liver quantitatively, we tried to predict the plasma concentration increasing ratio (R) of midazolam (MDZ) by erythromycin (EM), diltiazem (DLZ), or verapamil (VER) in rats. MDZ was administered through the portal vein at the steady state of plasma concentration of these inhibitors. The R values in the area under the plasma concentration curve of MDZ in the presence of EM, DLZ, and VER were 2.02, 1.64, and 1.30, respectively. The liver to plasma unbound concentration ratios of EM, DLZ, and VER at the steady state after infusion were 20.8, 1.02, and 3.01, respectively, suggesting concentrative uptake of EM and VER into the liver. The predicted R value in the presence of EM calculated by use of plasma unbound concentration was 1.03, whereas the value calculated with liver unbound concentration was 1.61, which was very close to the observed value. These findings indicated the need to consider the concentrative uptake of inhibitors into the liver for the quantitative prediction of metabolic inhibition. However, the predicted values in the presence of DLZ or VER calculated by use of liver unbound concentration were still underestimated. This result may be due to the metabolic inhibition by the metabolites of both inhibitors. Therefore, when predicting the degree of metabolic inhibition quantitatively, the inhibitory effect by coadministered drugs and the disposition of these metabolites in the liver must also be considered. The American Society for Pharmacology and Experimental Therapeutics