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The type of CYP2D6 function of an individual may influence the person's response to different doses of drugs that CYP2D6 metabolizes.

ultrarapid metabolizer – multiple copies of the CYP2D6 gene are expressed, so greater-than-normal CYP2D6 function occursĪ patient's CYP2D6 phenotype is often clinically determined via the administration of debrisoquine (a selective CYP2D6 substrate) and subsequent plasma concentration assay of the debrisoquine metabolite (4-hydroxydebrisoquine).

extensive metabolizer – normal CYP2D6 function.

intermediate metabolizers – metabolize drugs at a rate somewhere between the poor and extensive metabolizers.

poor metabolizer – little or no CYP2D6 function.

The CYP2D6 function in any particular subject may be described as one of the following: Pharmacogenomic tests are now available to identify patients with variations in the CYP2D6 allele and have been shown to have widespread use in clinical practice.

The genotype accounts for normal, reduced, and non-existent CYP2D6 function in subjects.

Genotype/phenotype variability ĬYP2D6 shows the largest phenotypical variability among the CYPs, largely due to genetic polymorphism. Alternatively spliced transcript variants encoding different isoforms have been found for this gene. Among them, CYP2D7P originated from CYP2D6 in a stem lineage of great apes and humans, the CYP2D8P originated from CYP2D6 in a stem lineage of Catarrhine and New World monkeys' stem lineage. near two cytochrome P450 pseudogenes (CYP2D7P and CYP2D8P). The gene is located on chromosome 22q13.1. If such a drug is taken at the same time as a second drug that is a CYP2D6 substrate, the first drug may affect the elimination rate of the second through what is known as a drug-drug interaction. Other drugs may function as inhibitors of CYP2D6 activity or inducers of CYP2D6 enzyme expression that will lead to decreased or increased CYP2D6 activity respectively. So, the dose of the drug may have to be adjusted to take into account of the speed at which it is metabolized by CYP2D6. If a drug is metabolized too quickly, it may decrease the drug's efficacy while if the drug is metabolized too slowly, toxicity may result. Hence, for drugs that are metabolized by CYP2D6 (that is, are CYP2D6 substrates), certain individuals will eliminate these drugs quickly (ultrarapid metabolizers) while others slowly (poor metabolizers). Ĭonsiderable variation exists in the efficiency and amount of CYP2D6 enzyme produced between individuals. This enzyme also metabolizes several endogenous substances, such as hydroxytryptamines, neurosteroids, and both m-tyramine and p-tyramine which CYP2D6 metabolizes into dopamine in the brain and liver.

In particular, CYP2D6 is responsible for the metabolism and elimination of approximately 25% of clinically used drugs, via the addition or removal of certain functional groups – specifically, hydroxylation, demethylation, and dealkylation. It is also highly expressed in areas of the central nervous system, including the substantia nigra.ĬYP2D6, a member of the cytochrome P450 mixed-function oxidase system, is one of the most important enzymes involved in the metabolism of xenobiotics in the body. CYP2D6 is primarily expressed in the liver. long-chain fatty acid biosynthetic processĬytochrome P450 2D6 ( CYP2D6) is an enzyme that in humans is encoded by the CYP2D6 gene.negative regulation of cellular organofluorine metabolic process.isoquinoline alkaloid metabolic process.