Dec. 27, 2004 – A new type of genetic test may help prevent dangerous drug interactions by allowing doctors to screen patients for potential drug metabolism problems before prescribing a drug.

The FDA approved the test, known as the AmpliChip Cytochrome P450 Genotyping Test, last week. Officials say the test will help doctors use genetic information to select the proper type and dose of drug to treat a variety of common illnesses, including heart disease, depression, and cancer.

The test screens DNA obtained from a patient’s blood sample for a family of genes that affects how well the liver breaks down certain drugs and other compounds. It’s the first DNA microarray test to be cleared by the FDA and others are expected to be developed in the future.

A microarray is similar to a computer microchip, but instead of tiny circuits, the chip contains millions of DNA molecules that determine a person’s DNA sequence for a particular gene.

“Physicians can use the genetic information from this test to prevent harmful drug interactions and to assure drugs are used optimally, which in some cases will enable patients to avoid less effective or potentially harmful treatment choices,” says Lester M. Crawford, MD, acting FDA Commissioner in a news release.

The test analyzes a gene called Cytochrome P450 that is active in the liver to break down drugs and other compounds. Variations in this gene can cause a person to metabolize drugs more quickly or slowly than normal, or in some cases, not at all. These differences in drug metabolism can lead to potential drug interactions, overdosing, or underdosing.

An enzyme in this gene family plays an important role in the body’s ability to metabolize commonly prescribed drugs such as antidepressants, antipsychotics, beta-blockers (used in treating heart disease), and some cancer chemotherapy drugs.

The test is made by Roche Molecular Systems, Inc., of Pleasanton, Calif. The FDA cleared the test for use with the Affymetrix GeneChip Microarray Instrumentation System, manufactured by Affymetrix, Inc., of Santa Clara, Calif.