- women of childbearing potential (less than two years post-menopausal or not surgically sterile for more than 3 months), had to prove a negative serum β-human chorionic gonadotropin (HCG) pregnancy test at screening and a negative urine β-HCG pregnancy test at day 1 on each of the treatment periods, had to use a highly effective method of birth control (failure rate less than 1% per year)