- All females of child-bearing potential must have a negative serum pregnancy test immediately prior to enrollment. In addition, all females of child-bearing potential must agree to be completely abstinent or be using an accepted form of contraception throughout the entire study period. Accepted forms of contraception are defined as those with a failure rate <1% when properly applied and include: combination oral pill, some intra-uterine devices, and a sterilised partner in a stable relationship. Female subjects must also not be actively breast-feeding through the entire study period.