The US Food and Drug Administration (FDA) has announced a two-year partnership with Medco, the nation’s largest pharmacy benefit manager (PBMP, to study the impact of genetics on the efficiency of many commonly-used prescription drugs.

The FDA and Medco will jointly develop research projects, programmes and strategies in the area of pharmacogenomics, to help predict how patients are likely to respond to a wide variety of drugs, including pain relievers, anticoagulants and cancer drugs.

"An increasing number of drugs are including genetic information in their labels and we're finding out how genes affect some drugs that have been widely used for generations. Studying this field can advance pharmacy care to remove some of the trial and error in how medications are prescribed," said Robert Epstein, chief medical officer of Medco, whose prescription drug benefit programs cover around one in five of the US population.

Unique differences in an individual's genes can cause variations in how many prescription drugs are metabolized in the body. This affects safety or efficacy, and can be dangerous or potentially deadly in the case of common medications like warfarin or codeine. Approximately 30% of all medications are metabolized by one enzyme, CYP2D6, which opens up a far-reaching range of genetic tests that could be used to determine how people will respond to a wide range of medications, says Medco.

Under the research agreement, which runs to end-August 2010, the PBM will deliver a series of pharmacogenomic testing reports to the FDA, addressing issues such as the safety of prescription drugs, physician participation in pharmacogenomics testing and the usefulness of the tests in prescribing, and quantifying prescription information about drugs that have genetic information in their labels. The reports will be derived from clinical settings, including one that will examine whether physicians are willing to change the dose of a prescription based on a genetic test result.

"Medco's partnership with the FDA should help establish gene testing as a tool to help lower health care costs and improve the quality of care. This will come from reducing waste from treatments that do not work and also from helping prevent unnecessary hospitalizations from incorrect dosages or other adverse drug events,” said Dr Epstein.

Medco currently has a research collaboration with LabCorp, which looking at is genetic consideration in breast cancer patients using tamoxifen and is due to complete this year, and another with the Mayo Clinic in the use of warfarin, scheduled for competition in 2009. The PBM plans to submit portions of the research from its partnership with the FDA to peer-reviewed journals for publication, with an eye on building the body of evidence supporting the value of gene testing.