- Women who are breast-feeding, pregnant, expect to become pregnant during the course of the study, or are sexually active in a heterosexual relationship and are not using a medically acceptable double barrier method birth control. Confirmation that the subject is not pregnant must be established by a negative serum beta-hCG pregnancy test result obtained during the Screening period. Pregnancy testing is not required for post-menopausal or surgically sterilized women. Women relying solely on oral contraceptives for birth control are excluded.