User:Anypodetos/Genetic polymorphisms affecting drug metabolism

Many pharmaceutical drugs are metabolized – activated or inactivated – by a number of enzymes in the human body, and moved in and out of cells by transporter proteins. Among other factors, genetic variation (polymorphisms) of these enzymes and transporters can cause drugs to be more or less effective in individual people than on average, or have more or fewer side effects. A group of enzymes commonly discussed in this context are the cytochromes P450 ("CYP"), most of which are found in the liver.

Extensive metabolizers
Extensive metabolizers with respect to a certain drug are people with a "normal" metabolism of this drug. This can be due to two functioning gene copies or alleles coding for the relevant enzyme (one from the father and one from the mother). Some drugs can also be metabolized normally if one or both alleles have reduced activity; for example, one normally functioning allele of the liver enzyme CYP2D6, or two with reduced activity, are sufficient for metabolizing amitriptyline.

Poor metabolizers
People with very low enzymatic activity are called poor metabolizers. Two inactive alleles