Patients of childbearing age who are unwilling to practice an effective form of contraception. Patients of childbearing potential must use an effective method of contraception while they are on-study; effective methods include intrauterine device (IUD), hormonal (birth control pills, injections, or implants), tubal ligation/hysterectomy (self or partner), partner's vasectomy, or barrier methods (condom, diaphragm, or cervical cap), or abstinence.