Cytochrome P450 2C19 (abbreviated CYP2C19), a member of the cytochrome P450 mixed-function oxidase system, is involved in the metabolism of xenobiotics in the body. It is involved in the metabolism of several important groups of drugs including many proton pump inhibitors and antiepileptics. In humans, the CYP2C19 protein is encoded by the CYP2C19gene.CYP2C19 acts on 5-10% of drugs in current clinical use.CYP2C19 is a liver enzyme that is responsible for metabolizing a wide variety of drugs including the anticoagulant clopidogrel (Plavix), antiulcer drugs such as omeprazole, antiseizure drugs such as mephenytoin, the antimalarial proguanil, and the anxiolytic diazepam.
This gene encodes a member of the cytochrome P450 superfamily of enzymes. The cytochrome P450 proteins are monooxygenases that catalyze many reactions involved in drug metabolism and synthesis of cholesterol, steroids and other lipids. This protein localizes to the endoplasmic reticulum and is known to metabolize many xenobiotics, including the anticonvulsive drug mephenytoin, diazepam and some barbiturates. Polymorphism within this gene is associated with variable ability to metabolize mephenytoin, known as the poor metabolizer and extensive metabolizer phenotypes. The gene is located within a cluster of cytochrome P450 genes on chromosome no.10 arm q24.
Genetic polymorphism (mainly CYP2C19*2, CYP2C19*3 and CYP2C19*17) exists for CYP2C19 expression, with approximately 3–5% of Caucasian and 15–20% of Asian populations being poor metabolisers with no CYP2C19 function. This may reduce the efficacy of clopidogrel.If there an abnormal CYP450 2C19 the certain Benzodiazepines should be avoided such as; Diazepam (Valium), Lorazepam (Ativan), Oxazepam (Serax) and Temazepam (Restoril).On the basis of their ability to metabolise (S)-mephenytoin or other CYP2C19 substrates, individuals can be classified as extensive metabolisers (EMs) or poor metabolisers (PMs).Eight variant alleles (CYP2C19*2 to CYP2C19*8) that predict PMs have been identified.
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