The influence ofCYP2C19polymorphisms on exacerbating effect of rabeprazole in celecoxib‐induced small bowel injury

BACKGROUND: Simultaneous use of proton pump inhibitors (PPIs) has been shown to increase the risk of nonsteroidal anti-inflammatory drug (NSAID)-induced small bowel injury. AIM: To investigate whether polymorphisms of the cytochrome P450 2C19 gene (CYP2C19), encoding a key metabolising enzyme for PPIs, are associated with small bowel injury induced by celecoxib in combination with the PPI rabeprazole. METHODS: Study participants included 55 healthy Japanese volunteers, who participated in the PPI-NSAID Kyushu University Study using video capsule endoscopy. For 2 weeks, 26 subjects were treated with celecoxib plus rabeprazole (rabeprazole group), and 29 subjects received celecoxib plus placebo (placebo group). All subjects were genotyped for CYP2C19 using real-time fluorescent polymerase chain reaction. Subjects were sub-classified as poor metabolizers or extensive metabolizers. The incidence and number of small bowel injuries were compared between poor metabolizers and extensive metabolizers in each group. RESULTS: In the rabeprazole group, the incidence of small bowel injuries was significantly higher in poor metabolizers than in extensive metabolizers (85.7% vs 31.6%, P=.026). The number of mucosal injuries in the rabeprazole group was also significantly higher in poor metabolizers compared with extensive metabolizers (median [range] 3 [0-31] vs 0 [0-7], P=.01). In addition, we found a significant interaction between CYP2C19 genotype and concomitant use of rabeprazole in subjects at risk for celecoxib-induced small bowel injury. CONCLUSIONS: The CYP2C19 genotype might be associated with the risk of small bowel injury when celecoxib is combined with rabeprazole.