- were on a stable form of contraception, defined as a stable oral contraceptive regimen for at least two months prior to enrollment; OR a transdermal contraceptive patch for at least three months prior to enrollment; OR long-acting progestins for at least six months prior to enrollment; OR had an intra-uterine device (IUD) inserted (with no vaginal or gynecological complaints associated with its use) at least three months prior to enrollment; OR had undergone surgical sterilization at least three months prior to enrollment; AND were willing to use oral contraceptives, if necessary, to avoid menstruation while taking part in this trial