- Unwillingness to use one (for males) or two (for females) reliable methods of contraception while engaging in heterosexual intercourse during the study. Acceptable methods for women include hormonal contraception (estrogen/progesterone or progesterone-only formulations) if stable for a year or more prior to study entry, intrauterine device, or barrier methods (condom, or diaphragm with spermicide). Acceptable methods for males include condom use. This requirement does not apply to women who have been post-menopausal for at least 24 consecutive months or have undergone surgical sterilization, or to men who have undergone surgical sterilization or have documented azoospermia.