The age of "personalized medi­cine" has arrived, but chances are your doctor doesn't know it yet. Existing tests can analyze patients' genetic makeup to provide guidance on whether certain drugs--such as codeine, antidepressants, and even some cancer medications--will help them, harm them, or do nothing. And a host of even newer "pharmacogenetic" tests are now in the R&D pipeline.

But the existing tests aren't widely ordered by doctors, a fact that bothers David Flockhart, chief of clinical pharmacology at the Indiana University School of Medicine. Flockhart, who has developed genetic tests to help guide the prescription of diabetes and high-blood-pressure drugs, says doctors are generally uneducated about the availability of such tests. But he predicts that that will change if the U.S. Food and Drug Administration recommends that doctors test two specific genes in all patients prescribed a widely used anticoagulant.