Women have smaller kidneys A lack of female participants in clinical trials and a failure to report separate results by gender could lead to drugs being marketed that are less effective for women , a study has warned . Jan Roeters - Lennep at Rotterdam 's Erasmus Medical Centre said the absence of women in clinical trials was a " blind spot " , while an analysis of 45 UK clinical trials revealed 82 % of the participants were women , and only five separated them by the sex of participants . Separate US research found that eight out of 10 drugs withdrawn from use after approval had higher risks for women .
A lack of female participants in clinical trials and a failure to report separate results by gender could lead to drugs being marketed that are less effective for women , a study has warned . Jan Roeters - Lennep at Rotterdam 's Erasmus Medical Centre said the absence of women in clinical trials was a " blind spot " , while an analysis of 45 UK clinical trials revealed 82 % of the participants were women , and only five separated them by the sex of participants . Separate US research found that eight out of 10 drugs withdrawn from use after approval had higher risks for women .