Nausea, fatigue, dizziness, dry mouth, insomnia. For people like me, who seem susceptible to every side effect possible, the tiny type on ads for new drugs is required reading. NyQuil puts me into a half-conscious delirium. Codeine makes me throw up. And back in college, when my doctor prescribed Wellbutrin to help me quit smoking, I experienced blurred vision and the worst headaches of my life.

Given that my troubled history with medication is shared by my mother and sister, I have long suspected a genetic basis for my sensitivity. So like many others, I have over the last few years eagerly anticipated the benefits of pharmacogenomics--a field whose researchers aim to let doctors tailor prescriptions to their patients' genetic makeups. It's 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.