Pharmacogenetics involves variations in drug response due to genetic makeup.
The activity of drug-metabolizing enzymes often varies widely among healthy people, making metabolism highly variable. Drug elimination rates vary up to 40-fold. Genetic factors and aging seem to account for most of these variations.
Pharmacogenetic variation (eg, in acetylation, hydrolysis, oxidation, or drug-metabolizing enzymes) can have clinical consequences (see table Examples of Pharmacogenetic VariationsGenetic, environmental, and developmental factors that can interact).
Examples of Pharmacogenetic Variations
Variation | Incidence | Examples of Effects |
|---|---|---|
Acetylation, fast | — | |
Acetylation, slow (drug inactivation by hepatic N-acetyltransferase) | About 50% of the US population | |
Aldehyde dehydrogenase-2 deficiency | About 50% of Japanese, Chinese, and other Asian populations | With alcohol ingestion, marked elevations of blood acetaldehyde, causing facial flushing, increased heart rate, diaphoresis, muscle weakness, and sometimes catecholamine-mediated vasodilation with euphoria |
CYP2C9 genetic polymorphisms | 30% in one study More common among East Asians | thrombosis in high-risk patients |
G6PD deficiency | 10% of males of African descent Higher prevalence in people of Mediterranean descent | |
Genetic polymorphisms of CYP2C9 and vitamin K epoxide reductase complex subunit 1 (VKORC1) | About 50% of a given population carries at least 1 allele | |
HLA-B*1502 | 1 to 6/10,000 in countries with mainly white populations In some Asian countries, about 10 times higher | |
Plasma pseudocholinesterase deficiency | About 1/1500 people | |
* In one study, variations in CYP2C9 or VKORC1 | ||
Genetic, environmental, and developmental factors that can interact, causing variations in drug response among patients
