Your doctor may use cytochrome P450 (CYP450) tests to help determine how your body processes (metabolizes) a drug. The human body contains P450 enzymes to process medications. Because of inherited (genetic) traits that cause variations in these enzymes, medications may affect each person differently.

Drug-gene testing — also called pharmacogenomics or pharmacogenetics — is the study of how genes affect your body's response to medication. Tests look for changes or variations in these genes that determine whether a medication could be an effective treatment for you or whether you could have side effects from a specific medication.

The P450 enzyme with the most variation in different people is the CYP2D6, which processes many antidepressants and antipsychotic medications. By checking your DNA for certain gene variations, CYP450 tests can offer clues about how your body may respond to a particular antidepressant. Other CYP450 tests are available for other enzymes.

CYP450 and other genetic tests (genotyping tests) are becoming more common as doctors try to understand why antidepressants help some people and not others. While their use might be increasing, there are limitations.

Aug. 21, 2015