Participation of Women in Clinical Trials of Drug Therapies: A Context for the Controversies

Marianne N. Prout, MD, MPH, Susan S. Fish, PharmD, MPH

In This Article


What is equity in clinical trials? We believe that counting the number of participants in all clinical trials by sex is inadequate. Sex-specific research, such as research on pregnancy and menopause, is predominantly aimed at women and makes the simple counts of research participants meaningless. Counting participants in non-sex-specific studies changes the perception that women are overrepresented. On the other hand, counting the number of studies of sex-specific topics may overrepresent women because of greater attention to disorders of the female reproductive system than of the male system. Premenopausal women still face barriers to participation in trials of early development of drugs, ie, phase 1, and phase 2 trials. Phase 3 trials enroll so many participants compared with early-phase studies, however, that equity in access to early drug trials cannot be assessed by simply counting the number of women who participate in clinical trials.

Progress in the inclusion of women in clinical trials has followed the changes in policies and regulations over the past 15 years. Because restrictions on women in clinical trials have changed recently, however, many drug therapies and their effects on women need to be reassessed. In addition, reversals in current regulations remain a concern -- for example, the research participation of pregnant women. Finally, participation is not sufficient. Sex-specific analyses are required to ensure that differences in response rates, adverse events, or drug interactions are recognized. Sex-specific analyses are equally important so that drugs that are effective in only 1 sex are not rejected because of pooling of data.

We recommend that the requirements for inclusion in phase 3 trials be expanded to include earlier-phase drug and medical device studies. In addition, the increased study sample size required to perform adequate sex-specific analyses must be supported by funding agencies, both federal and commercial. We also recommend expansion of monitoring of the participation of women and minorities to include all phases of clinical trials. The federal tracking of clinical trials should be complemented with monitoring by concerned researchers and IRBs. The unequal sex distribution in trials in medical subspecialty areas suggests that smaller trials addressing less prevalent medical problems may still not include women or analyze results separately. Specialists and subspecialists who are familiar with the particular issues for women in their fields need to monitor studies in their areas of expertise.

We applaud the recent recommendations of the Institute of Medicine to encourage research on sex differences broadly, from cellular to clinical studies. We commend the creation of an accessible database of the demographic characteristics of clinical trial participants by federal agencies. We urge clinicians, researchers, and research participants to utilize these resources to advance knowledge in women's health.


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