To compare the potency and specificity of omeprazole (OME) and lansoprazole (LAN) as inhibitors of cytochrome P450 isoforms, we performed human liver microsomal assays on CYP2C19 (S-mephenytoin 4-hydroxylation), CYP2C9 (tolbutamide 4-hydroxylation), CYP3A (dextromethorphan N-demethylation),CYP2D6(dextromethorphan O-demethylalion) and CYP1A2 (phenacetin O-deethylation). Both drugs were potent, competitive inhibitors of CYP2C19. For OME, the upper limit of 'window of selectivity' was at least 20 times greater than the Ki. While both drugs showed similar inhibitory effects on CYP2C9 and CYP3A, LAN showed at least 5 times more potent inhibition of CYP2D6. No inhibition of CYP1A2 was noted. Inhibitory constants(Ki ± SD, μM) were as follows: P450 isoforms OME LAN CYP2C19 3.1 ± 2.2 3.2 ± 1.3 CYP2C9 40.1 ± 14.8 52.1 ±1.4 CYP3A 84.4 ± 4.0 170.4 ± 7.1 CYP2D6 240.7 ± 102.0 44.7 ± 22.0 OME appears to be a useful, selective inhibitor of CYP2C19 because of its potency and broad 'window of selectivity'. While effects on other cytochrome P450 isoforms are similar, these data suggest that LAN may be the more important inhibitor of CYP2D6.
|Original language||English (US)|
|Number of pages||1|
|Journal||Clinical Pharmacology and Therapeutics|
|State||Published - Dec 1 1997|
ASJC Scopus subject areas
- Pharmacology (medical)