Until recently, women with HIV, particularly pregnant women, were excluded from many drug trials on the grounds that experimental compounds could cause birth defects, and that women's hormonal cycling might interfere with data collection. Drug companies fear expensive lawsuits related to birth defects, and often require women of child-bearing age seeking entry into a drug trial to take birth control. They've also been reluctant to pay for day care or transportation, factors that limit womens' participation in drug trials. As it stands, much of the information we have gleaned about HIV drugs is based on how they affect adult male bodies. Women's body composition can impact drug potency and side effects.
Women generally weigh less than men and have a higher fat and water content in their bodies.
Their reproductive systems are also different. Menstrual periods, menopause, and pregnancy all cause major changes in women's body chemistry that can affect how drugs are absorbed and where they are distributed. But we may be blasting women with higher doses than we need to. It is also likely that women have different side effects. Experts and women's health advocates remain unconvinced.