- Female subjects of childbearing potential who have a negative urine pregnancy test, and are willing to use an acceptable form of birth control during the study. For the purpose of this study, a female of childbearing potential is a female who is not postmenopausal for greater than 2 years, has not had a tubal ligation, and has not had a hysterectomy. For the purpose of this study, the following are considered acceptable methods of birth control: