Medicine Gets Personal

For most of history, medicine was one-size-fits-all — everyone with the same disease got the same drug at the same dose. But people metabolize drugs differently because of genetic variations in their liver enzymes.

A small share of people — and far more in some populations — carry a variant of the CYP2D6 enzyme that makes them ultra-rapid metabolizers of codeine. They convert it to morphine so fast it can cause overdose at normal doses.