Women have hormonal cycles, smaller organs, higher body fat composition — all of which are thought to play a role in how drugs affect our bodies. We also have basic differences in gene expression, which can make differences in the way we metabolize drugs. For example, men metabolize caffeine more quickly, while women metabolize certain antibiotics and anxiety medications more quickly. In some cases, drugs work less effectively depending on sex; women are less responsive to anesthesia and ibuprofen for instance. In other cases, women are at more risk for adverse — even lethal — side effects.
Source: The New York Times.