Genes and the Response to Drugs

The response to many drugs in common use varies greatly among patients. After the intake of identical doses of a given agent, some patients may have clinically significant adverse effects, whereas others may have no therapeutic response. Some of this diversity in rates of response can be ascribed to differences in the rate of drug metabolism, particularly by the cytochrome P-450 superfamily of enzymes. Ten isoforms of cytochrome P-450 are responsible for the oxidative metabolism of most drugs, each having selective yet overlapping substrate specificity. Variability among patients in the activity of these enzymes reflects a complex interaction between environmental . . .