Genetic polymorphism of CYP2C19 & therapeutic response to proton pump inhibitors.

Proton pump inhibitors (PPIs) are extensively metabolized in the liver by CYP2C19, that demonstrates genetic polymorphism with 21 mutant alleles. The subjects can be divided into 2 groups with respect to CYP2C19 phenotypes viz., extensive metabolizers (EMs) and poor metabolizers (PMs) of PPIs. This division results in marked interindividual variations in the pharmacokinetics and pharmacodynamics of PPIs in the population. Intragastric pH values and the plasma concentration of PPIs after oral ingestion were significantly lower in EMs namely normal homozygotes (CYP2C19*1/*1) and heterozygotes (CYP2C19*1/*X) compared to PMs namely mutant homozygotes (CYP2C19*X/*X) where 'X' represents the mutant allele. Hence, association has been found between the genetic polymorphism of CYP2C19 and therapeutic response to PPIs. CYP2C19 polymorphism affected eradication of Helicobacter pylori using diferent PPI based eradication therapies as PM patients demonstrated significantly higher eradication rates compared to EMs. CYP2C19 genetic polymorphism also affects the therapeutic outcome of gastroesophageal reflux disease (GERD), reflux oesophagitis and duodenal ulcers. For optimal therapeutic response with PPIs, CYP2C19 pharmacogenetics should be taken into consideration. This shall help in the prescription of optimal doses of PPIs, thus paving the way for personalized medication.