Rabeprazole 10 mg twice daily, not 20 mg once daily, should be administered to achieve more potent and long-lasting acid suppression.

Rabeprazole, omeprazole, and lansoprazole, given once daily at standard doses, cannot be expected to achieve ideal acid suppression for the initial therapy for gastroesophageal reflux disease in Helicobacter-negative CYP2C19 homozygous extensive metabolizers. Rabeprazole 10 mg may be appropriate for step-down therapy.

SUMMARYBackground: 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 ¼ 6) and the others [homozygous extensive metabolizers (homo-EMs, n ¼ 6) and heterozygous extensive metabolizers (hetero-EMs, n ¼ 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.

Acid-suppressive effects of some brands of generic omeprazole are not the same as original omeprazole. These differences might be reflected in clinical outcomes.