- Patients of childbearing potential must have a negative pregnancy test prior to the study entry and be practicing an effective form of contraception; sexually active subjects must agree to use medically accepted barrier methods of contraception (e.g., male or female condom) during the course of the study and for 4 months after the last dose of study drug, even if oral contraceptives are also used; all subjects of reproductive potential must agree to use both a barrier method and a second method of birth control during the course of the study and for 4 months after the last dose of study drug; pregnant women are excluded from this study