* Illustration: Martin Woodtli * Side effects may include nausea and drowsiness. Or something worse: Consider the heart attacks linked to the antiarthritis drug Vioxx before it was pulled from pharmacy shelves in 2004, and the potentially fatal skin blisters penicillin can trigger.
The truth is, most medicines are blunt instruments, and no one really knows what they'll do once they're inside you. Drugs work by either supplementing or inhibiting a natural chemical process that's out of whack. But the chemicals involved can play multiple roles, which means the effects can ripple through your body, causing anything from blood clots to vomiting.
Complications may also occur if a drug binds to something other than its intended target. Viagra, for example, works by targeting PDE5 molecules in the penis. However, it also attaches weakly to PDE6 molecules in the cone cells of the retina, lending some men a blue-tinted view. Even your own DNA can screw things up sometimes. A slight variation in your genetic makeup could allow a drug to stay in your body too long, leaving you with a medicinal hangover.
But the future of medicine is brighter: Hi-res imaging of the molecules that drugs target — a technology that's just starting to come online — will allow pharmaceutical companies to design meds that attach only where they're supposed to. And the emerging field of pharmacogenomics aims to build pills that are just for you.
