It was only eight years ago that the Food and Drug Administration required drugs to be tested on women as well as men. Research since then has yielded astonishing results: All kinds of drugs act differently in women. For instance, women may require larger doses of anti-inflammatories, like ibuprofen, but lower doses of the antidepressants that affect the mood-regulating neurotransmitter serotonin. And while low-dose aspirin helps prevent heart attacks in men, it’s more effective at preventing strokes in women.

There appear to be some basic differences in male and female metabolisms involving stomach acidity and gastric-emptying rates, which may affect how quickly drugs dissolve and enter the bloodstream. But many of the reasons for the differences depend on the drug involved.

If you’re concerned about getting the right dosage of an over-the-counter or prescription medication, talk to your doctor or a well-informed pharmacist, suggests neuroscientist Sharon C. Wilsnack. And always read the fine print on the material that comes with prescription drugs; sometimes it will break out the side effects for men and women.