Finasteride 1 mg Has No Inhibitory Effect on Omeprazole Metabolism in Extensive and Poor Metabolizers for CYP2C19 in Japanese

The study investigated whether finasteride, a drug used to treat hair loss, inhibits the metabolism of omeprazole, a drug used to treat acid reflux, in Japanese individuals with different metabolizer types for CYP2C19. The study found that finasteride had little inhibitory effect on omeprazole metabolism in either group, indicating that finasteride has little inhibitory effect on CYP2C19 activity in vivo at the dose of 1 mg/day. Therefore, it was confirmed that multiple oral doses of finasteride at 1 mg/day did not affect in vivo CYP2C19 activities in humans. The study concluded that a multiple dose of finasteride 1 mg with a single dose of omeprazole 20 mg is as safe as with the administration of omeprazole 20 mg alone.