- Female subjects of child bearing potential willing to participate commit to use a double-barrier method of contraception. One of the following methods is acceptable as the sole method of contraception if there is indisputable data that it is >99% effective, otherwise it should be used with a barrier method (condom or occlusive cap (diaphragm or cervical/vault caps) used with spermicidal foam/gel/film/cream/suppository): Documented tubal ligation. Documented placement of an IUD or IUS. Male partner sterilisation prior to the female subject's entry into the study and is the sole partner for that female subject.