We have discussed how an enzyme important to the metabolic pathway of a certain drug can be deficient or defective due to hereditary factors (polymorphisms) and how these deficiencies can cause the drug to accumulate in the body (as seen in “poor metabolizers”) or have reduced efficacy (as seen in “ultrarapid metabolizers”).
Genetics can also indirectly influence the biotransformation of a drug. Genetic variation in the genes that control the synthesis of drug-receptor sites can affect the concentration of free drug in the bloodstream that is available for metabolic processes. Genetic mutations in carrier proteins (such as albumin) can also affect circulating drug levels. The bioavailability of the drug can also be affected by variation in genes that control the synthesis of proteins available for protein binding.
