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Effect of omeprazole 10 mg on intragastric pH in three different CYP2C19 genotypes, compared with omeprazole 20 mg and lafutidine 20 mg, a new H 2 ‐receptor antagonist
Author(s) -
Shimatani T.,
Inoue M.,
Kuroiwa T.,
Horikawa Y.,
Mieno H.,
Nakamura M.
Publication year - 2003
Publication title -
alimentary pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.308
H-Index - 177
eISSN - 1365-2036
pISSN - 0269-2813
DOI - 10.1046/j.1365-2036.2003.01804.x
Subject(s) - omeprazole , cyp2c19 , potency , proton pump inhibitor , medicine , pharmacology , antagonist , gastroenterology , chemistry , receptor , metabolism , biochemistry , cytochrome p450 , in vitro
Summary Background : Omeprazole 10 mg is used as maintenance therapy for gastro‐oesophageal reflux disease, but previous reports have not mentioned the potency of its acid suppression. Aim : To evaluate the potency of acid suppression with omeprazole 10 mg, in relation to CYP2C19 genotypes. Methods : Eighteen healthy subjects without Helicobacter pylori participated. After a 7‐day regimen of omeprazole 10 mg, 20 mg, lafutidine 20 mg (a novel H 2 ‐receptor antagonist) or water only (baseline data), intragastric pH was measured for 24 h. Results : With omeprazole 10 mg, greater differences were observed than 20 mg in median pH values and pH > 4 holding time ratios between poor metabolizers (PMs, n = 6) and the others [homozygous extensive metabolizers (homo‐EMs, n = 6) and heterozygous extensive metabolizers (hetero‐EMs, n = 6)]. With lafutidine 20 mg, these parameters were not influenced by the genotype. The potency of acid suppression was: omeprazole 20 mg ≈ lafutidine 20 mg > omeprazole 10 mg in homo‐EMs, omeprazole 20 mg > omeprazole 10 mg ≈ lafutidine 20 mg in hetero‐EMs, and omeprazole 20 mg ≈ omeprazole 10 mg > lafutidine 20 mg in PMs. Conclusions : Omeprazole 10 mg strongly suppresses acid secretion, but depending on the CYP2C19 genotypes shows greater interindividual variations in suppression than 20 mg.