Acid-suppressive effects of rabeprazole: comparing 10mg and 20mg twice daily in Japanese Helicobacter pylori-negative and -positive CYP2C19 extensive metabolisers

Rabeprazole 10mg b.i.d. is often administered as therapy for eradication of Helicobacter pylori (H. pylori) and is also proposed as therapy for refractory gastro-oesophageal reflux disease. However, there has not been a comprehensive assessment of its acid-suppressive effects. To compare the acid-suppressive effects of rabeprazole 10mg b.i.d. with 20mg b.i.d. considering H. pylori status. Thirteen H. pylori-negative and eleven H. pylori-positive Japanese CYP2C19 extensive metabolisers (3.0, >4.0, >5.0, >6.0, and >7.0 for 24h, no significant differences were observed between the two doses in either H. pylori-negative or H. pylori-positive subjects. At either dose, these parameters were significantly higher in H. pylori-positive subjects than in H. pylori-negative subjects. Nocturnal acid breakthrough occurred in seven and two of the thirteen H. pylori-negative subjects and one and two of the eleven H. pylori-positive subjects at each dose, respectively. The effects of rabeprazole 10mg b.i.d. were equal to those of 20mg b.i.d. in H. pylori-positive subjects; whereas in H. pylori-negative subjects, 20mg b.i.d. was superior for prevention of nocturnal acid breakthrough.