Typically, people have two copies of each gene. However, some people have hundreds or even thousands of copies of the CYP2D6 gene. Those with extra copies produce too much of the CYP2D6 enzyme and process the drug very fast. As a result, their bodies may convert codeine to morphine so quickly and completely that a standard dose can be an overdose. In contrast, some variants of CYP2D6 create an enzyme that doesn’t work. People with these variants process codeine slowly, if at all, leading to little, if any, pain relief. For them, doctors can prescribe a different drug.
How is pharmacogenomics affecting drug design, development, and prescribing guidelines?
The Food and Drug Administration (FDA) monitors drug safety in the United States. It now includes pharmacogenomic information on the labels of
around 200 medications. This information can help doctors tailor drug prescriptions for individual patients by providing guidance on dose, possible side effects, or differences in effectiveness for people with certain gene variants.
Drug companies are also using pharmacogenomics to develop and market medicines for people with specific genetic profiles.By studying a drug only in people likely to benefit from it, drug companies might be able to speed up the drug’s development and maximize its therapeutic benefit.
In addition, if scientists can identify genes that cause serious side effects, doctors could prescribe those drugs only to people who do not have those genes. This would allow some individuals to receive potentially lifesaving medicines that otherwise might be banned because they pose a risk for other people.