[The effect of proton pump inhibitor on intragastric acidity and it relation to S-mephenytoin hydroxylase genetic polymorphism].

OBJECTIVE: To study the effect of proton pump inhibitor rabeprazole (Rab) and omeprazole (Ome) on intragastric acidity and it relationship to S-mephenytoin hydroxylase (CYP2C19) genetic polymorphism.

METHODS: Thirty duodenal ulcer patients were randomly divided into two groups. They were treated by the following strategies: Rab 10mg or Ome 20mg twice daily orally for two days. Intragastric pH over 24 hours was recorded from morning of the second day. Blood CYP2C19 genotyping of each patient was detected by PCR-restriction enzyme analysis.

RESULTS: In Rab group, the mean intragastric pH values of the PM, hetEM and homEM were 6.3 +/- 0.1, 6.1 +/- 0.2, 6.0 +/- 0.1, no significant difference was observed among the three different genotype groups. In Ome group, they were 6.3 +/- 0.1, 5.9 +/- 0.2, 5.6 +/- 0.3. The differences were significant (P < 0.05). After treated with Rab for 24 hours, the mean and median 24 h intragastric pH values were significant higher than that of Ome (6.1 +/- 0.2, 6.1 +/- 0.3 vs 5.8 +/- 0.4, 5.7 +/- 0.4, P < 0.05). The reason was that big difference existed in homEM type between Rab (6.0 +/- 0.1) than Ome (5.6 +/- 0.3) group. NAB occurred in 3 patients of each group. The sustaining time of NAB in Rab group was shorter than that of Ome group [(2.6 +/- 0.2) h vs (3.4 +/- 0.6) h].

CONCLUSIONS: The effect of Rab on control of intragastric pH was less affected by an individual's CYP2C19 status. Both Rab and Ome could not overcome NAB, but Rab could shorten the sustaining time of nocturnal acid breakthrough.