Helicobacter pylori infection is the main cause of gastritis and peptic ulcer disease, and it is recognized as one of the most significant risk factors for gastric cancer. It has been observed that gene polymorphisms of cytochrome P450 2C19 (CYP2C19), which plays an important role in PPI (proton pump inhibitors) metabolism, are associated with the clinical efficacy of PPI-based therapies.

Different clinical relevant studies have been performed to determine if variants in CYP2C19 affect the elimination of H. pylori from the organism.

One of these studies consisted in a meta-analysis to determine whether CYP2C19 polymorphisms affect H. pylori eradication with antibiotic treatments based on proton pump inhibitors, such as lansoprazole, in English and Chinese individuals. In this study a large amount of literature data was included affecting many different populations and it was concluded that there was a significant difference in the elimination of the bacteria. The results showed better elimination in poor metabolizers and worse elimination in fast and intermediate metabolizers. This is due to the shorter exposure time of lanzoprazole in fast and intermediate metabolizers.

The frequency of different genotypes varies widely among different ethnic populations. The frequency of slow or poor metabolizers (PM) is below 4% in the black and white population, and above 14% in the Asian population. The frequency of rapid metabolizers is approximately 70% in Caucasians but only 30-40% in Asians.

CYP2C19 * 2 and CYP2C19 * 3 alleles are found in frequencies of 28.6% and 8.8% respectively in Asians; 12.8-16.1% and 0.1% respectively in Europeans.

Another clinical study that used data from 472 patients of diverse ethnicities (Caucasians, Japanese, Chinese, Americans, Jordanians) concluded the same results.

Thus we can say that individuals with CYP2C19 * 1 / * 1 (homozygous extensive metabolizers) genotypes or with CYP2C19 * 1 / * 2 or CYP2C19 * 1 / * 3 (heterozygous extensive metabolizers) genotypes respond worse to lansoprazole treatment, the drug remains during less time exposed to the organism and therefore a rigorous dose adjustment is necessary to achieve a good eradication response. On the other hand, for poor metabolizers, since the drug remain during more time exposed, a dose adjustment is required to avoid side effcets.

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