- Female subjects must be of non-child bearing potential (i.e. physiologically incapable of becoming pregnant, including women who are post-menopausal) or of child-bearing potential with a negative blood pregnancy test at screen and who agree to use a proven barrier method of contraception (e.g. spermicide plus condom) during the study period. Hormonal contraceptives will not be considered sufficient forms of contraception for this study. All subjects participating in this study should be counselled on the practice of safe or safer sex.