- Are males or females 18 years of age or older (If female, must be practicing abstinence or using a medically acceptable form of contraception (e.g., intrauterine device, hormonal birth control, or double barrier method). For the purpose of this study, all females are considered to be of childbearing potential unless they are post-menopausal, biologically sterile, or surgically sterile (i.e., hysterectomy, bilateral oophorectomy), or have undergone tubal ligation for greater than or equal to one year.)