Pharmacogenomics–a field whose researchers aim to let doctors tailor prescriptions to their patients’ genetic makeups–is one of the most tantalizing promises of the genomic era: quick and easy tests that tell you which drugs to take or what dose is right for you.

A few tests have been developed for specific diseases, such as cancer–most notably a genetic test that predicts which lung cancer patients will respond to some medications. But a new product, marketed by Roche and approved by the U.S. Food and Drug Administration in January 2005, now has the potential to begin making pharmacogenomics broadly accessible.

Called the AmpliChip CYP450 assay, it uses genetic analyses to ascertain how quickly people metabolize certain drugs, thus predicting who is most likely to experience unpleasant or even toxic side effects.