- Female subjects who are at risk of becoming pregnant must agree to use an effective method of contraception such as double barrier contraception, an injectable, combined oral contraceptive or an intra-uterine device (IUD). The subject must agree to use the contraception during the whole period of the study and for eight months after the last study drug administration. Non childbearing potential is defined as being postmenopausal for at least 1 year, or permanently sterilized at least 3 months before study entry.