Narrator: This is Science Today. In a discovery noted around the world, Dr. Jon Levine of the University of California, San Francisco found that men and women responded differently to a type of pain reliever called a kappa-opioid: it helped women and didn't help men. It was the first time anyone had linked pain relief with gender. And Levine says in the future, doctors who prescribe painkillers might take other variables into account, too.

Levine: I think it's also important to know -- and we don't know yet -- whether they differ as a function of the age of patient. Whether in children versus older individuals the agents that we use should be different. We don't know at this point whether they differ by the race of an individual.

Narrator: Levine says those characteristics might be more important than we know.

Levine: In general we've thought, well, if somebody has cancer pain or arthritis pain, that determines how we should treat it. And we've not really taken into the equation whether or not somebody is female or male, whether or not they are young or old, and what their racial background may be.

Narrator: For Science Today, I'm Steve Tokar.