| Abstrakt: |
The drug interactions between four human immune deficiency virus (HIV-1) protease inhibitors have been characterized by in-vitro metabolic studies using rat liver microsomal fractions and in-vivo oral administration. In this study, a new HPLC analytical method developed by us was used for the simultaneous determination of saquinavir and nelfinavir in rat plasma and microsomes.The metabolic clearance rates (Vmax/Km) of saquinavir, nelfinavir, and indinavir were 170.9 ± 10.9, 126.1 ± 4.4, and 73.0 ± 2.0 μL min−1(mg protein)−1, respectively. Ritonavir was the strongest inhibitor with inhibition constants (Ki) of 1.64 μM for saquinavir, 0.95 μM for indinavir, and 1.01 μM for nelfinavir. Nelfinavir was the second strongest inhibitor with Ki's of 2.35 μM for saquinavir and 2.14 μM for indinavir. Indinavir was the third strongest inhibitor with Ki's of 2.76 μm for nelfinavir and 3.55 μM for saquinavir. Saquinavir was the weakest inhibitor for the other three HIV-1 protease inhibitors. After oral co-administration in combination with another HIV-1 protease inhibitor, the AUCs of saquinavir, indinavir, and nelfinavir were significantly increased compared with mono-treatment. The AUCs of saquinavir were increased about 10.1-, 3.1- and 45.9-fold in the presence of indinavir, nelfinavir and ritonavir, respectively. The AUCs of indinavir were increased about 6.8-, 5.9- and 9.4-fold in the presence of nelfinavir, saquinavir and ritonavir, respectively. The AUCs of nelfinavir were increased about 2.2-, 6.6- and 8.5-fold in the presence of indinavir, saquinavir and ritonavir, respectively.The in-vivo effects observed after co-administration of two kinds of HIV-1 protease inhibitor were not always expected from in-vitro data, suggesting the presence of other interaction processes besides metabolism in the liver. These results provide useful information for the treatment of AIDS patients receiving combination therapy with two HIV-1 protease inhibitors. |
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