Table 1

Effects of loratadine, desloratadine, and 3-OH-desloratadine on CYP activities in human hepatic microsomes

Cytochrome P-450, Percentage of Control
10 μM LOR118.686.999.426.468.745.1
IC50LOR≥10 μM≥10 μM≥10 μM≅0.76 μM≥10 μM≅8.1 μM
10 μM DL84.080.0110.4112.5106.386.3
IC50DL≥10 μM≥10 μM≥10 μM≥10 μM≥10 μM≥10 μM
10 μM 3-OH-DL75.390.098.2101.489.597.9
IC503-OH-DL≥10 μM≥10 μM≥10 μM≥10 μM≥10 μM≥10 μM

The IC50 experiments were run at approximateKm values established in our laboratory for pooled human liver microsomes and, in general, correspond withKm values found in the literature: [3A4-dextromethorphan] Schmider et al., 1997; [3A4-testosterone]Wang et al., 1997; [1A2] Lin et al., 2001; [2C19] Easterbrook et al., 2001; [2C9] Tang et al., 2000; [2D6] Hickman et al., 1998.