Kyoichi Ohashi

CYP2C19 genotype status and effect of omeprazole on intragastric pH in humans

Omeprazole is metabolized by genetically determined S‐mephenytoin 4′‐hydroxylase (CYP2C19) in the liver. This study aimed to determine whether the effect of omeprazole on intragastric pH depends on CYP2C19 genotype status.

Effect of genotypic differences in CYP2C19 on cure rates for Helicobacter pylori infection by triple therapy with a proton pump inhibitor, amoxicillin, and clarithromycin

Proton pump inhibitors such as omeprazole and lansoprazole are mainly metabolized by CYP2C19 in the liver. The therapeutic effects of proton pump inhibitors are assumed to depend on CYP2C19 genotype status.

Effects of CYP2C19 genotypic differences in the metabolism of omeprazole and rabeprazole on intragastric pH

Omeprazole is mainly metabolized in the liver by CYP2C19, a genetically determined enzyme, whereas rabeprazole is mainly reduced non‐enzymatically and partially metabolized by CYP2C19. The therapeutic effects of rabeprazole are therefore assumed to be less affected by an individual’s CYP2C19 status.

Effect of cytochrome P4502C19 genotypic differences on cure rates for gastroesophageal reflux disease by lansoprazole

The acid‐inhibitory effect of lansoprazole depends on differences in cytochrome P450 (CYP) 2C19 genotypes. We assessed whether therapeutic effects of lansoprazole on gastroesophageal reflux disease (GERD) depended on the CYP2C19 genotype status in relation to the grade of GERD.

Pharmacogenomics-based Tailored versus standard therapeutic regimen for eradication of H. pylori

Helicobacter pylori eradication rates by triple therapy with a proton pump inhibitor, amoxicillin, and clarithromycin at standard doses depend on bacterial susceptibility to clarithromycin and patient CYP2C19 genotypes. We examined the usefulness of a personalized therapy for H. pylori infection based on these factors as determined by genetic testing. First, optimal lansoprazole dosing schedules that would achieve sufficient acid inhibition to allow H. pylori eradication therapy in each of different CYP2C19 genotype groups were determined by a 24‐h intragastric pH monitoring. Next, 300 H. pylori‐positive patients were randomly assigned to the standard regimen group (lansoprazole 30 mg twice daily (b.i.d.)), clarithromycin 400 mg b.i.d., and amoxicillin 750 mg b.i.d. for 1 week) or the tailored regimen group based on CYP2C19 status and bacterial susceptibility to clarithromycin assessed by genetic testing. Patients with failure of eradication underwent the second‐line regimen. The per‐patient cost required for successful eradication was calculated for each of the groups. In the first‐line therapy, the intention‐to‐treat eradication rate in the tailored regimen group was 96.0% (95% CI=91.5–98.2%, 144/150), significantly higher than that in the standard regimen group (70.0%: 95% CI=62.2–77.2%, 105/150) (P<0.001). Final costs per successful eradication in the tailored and standard regimen groups were

Calcium signalling in endothelial cells

669 and

Effects of genotypic differences in CYP2C19 status on cure rates for Helicobacter pylori infection by dual therapy with rabeprazole plus amoxicillin.

657, respectively. In conclusion, the pharmacogenomics‐based tailored treatment for H. pylori infection allowed a higher eradication rate by the initial treatment without an increase of the final per‐patient cost for successful eradication. However, the precise cost‐effectiveness of this strategy remains to be determined.

Effect of high‐dose lansoprazole on intragastic pH in subjects who are homozygous extensive metabolizers of cytochrome P4502C19

Vascular endothelial cells are ubiquitous for their presence in each and every vessel and unique for their multifunctional nature. A large number of endothelial functions depend to various extents on changes in intracellular Ca(2+) concentration. Reviewed are endothelial Ca(2+) stores, Ca(2+) channels, and in-out-in Ca(2+) signalling events, from ligand-binding on the plasma membrane into depletion of intracellular Ca(2+) stores and therefrom out to transplasmalemmal Ca(2+) entry that is of prime importance for many endothelial functions. Special emphasis is placed on mechanisms regulating store-operated Ca(2+) entry including a Ca(2+) influx factor, the vesicle secretion-like model, the conformational coupling model, the membrane potential, cytochrome P450, protein tyrosine kinase, myosin light chain kinase and nitric oxide.

Different dosage regimens of rabeprazole for nocturnal gastric acid inhibition in relation to cytochrome P450 2C19 genotype status

Rabeprazole is a potent proton pump inhibitor and is mainly reduced to thioether rabeprazole by a non-enzymatic pathway and partially metabolized to demethylated rabeprazole by CYP2C19 in the liver. We intended to determine a cure rate for Helicobacter pylori infection by dual rabeprazole/amoxicillin therapy in relation to CYP2C19 genotype status prospectively. Ninety-seven patients with gastritis and H. pylori infection completed the dual therapy with 10 mg of rabeprazole bid and 500 mg of amoxicillin tid for 2 weeks. At 1 month after treatment, cure of H. pylori infection was assessed on the basis of histology, a rapid urease test, culture, polymerase chain reaction (PCR), and 13C-urea breath test. CYP2C19 genotype status was determined by a PCR-restriction fragment length polymorphism method. Of the 97 patients, 33 were homozygous extensive metabolizers (homEM), 48 were heterozygous extensive metabolizers (hetEM), and 16 were poor metabolizers (PM). Cure of H. pylori infection was achieved in 79 of the 97 patients (81.4%, 95%CI = 71.9-88.7). Significant differences in cure rates among the homEM, hetEM, and PM groups were observed; 60.6% (95%CI = 42.1-77.3), 91.7% (95%CI = 80.0-97.7), and 93.8% (95%CI = 69.8-99.8), respectively (P = 0.0007). Twelve patients without cure after initial treatment (10 homEMs and 2 hetEMs) were successfully retreated with rabeprazole 10 mg q.i.d. and amoxicillin 500 mg q.i.d. for 2 weeks. The cure rates for H. pylori infection by dual rabeprazole/amoxicillin therapy depended on the CYP2C19 genotype status. This dual therapy appears to be effective for hetEM and PM patients. However, high dose dual rabeprazole/amoxicillin therapy was effective even for homEM patients. Therefore, the genotyping test of CYP2C19 appears to be a clinically useful tool for the optimal dual treatment with rabeprazole plus amoxicillin.

Sildenafil for primary and secondary pulmonary hypertension.

Lansoprazole is mainly metabolized by cytochrome P4502C19 (CYP2C19) in the liver. The effect of lansoprazole is assumed to be insufficient in subjects who are homozygous extensive metabolizers of CYP2C19. This study aimed to examine whether the CYP2C19 genotype status affected the acid‐inhibitory effects of lansoprazole and to develop a strategy to overcome this pharmacogenetic problem.