- Females with childbearing potential must have a negative pregnancy test before and during the study period. Sexually active females must be using an effective form of birth control or abstinence. These methods include oral contraceptives ("the pill"), an intrauterine device (IUD), levonogestrel implants (Norplant®), medroxyprogesterone acetate injections (Depo-provera®) or contraceptive foam with a condom.