- Subject is not using adequate contraceptive precautions during the study and for up to 1 month after the last dose of the study medication. A highly effective method of birth control is defined as those which result in a low failure rate (i.e., less than 1% per year) when used consistently and correctly such as implants, injectables, combined oral contraceptives, some intra-uterine devices, sexual abstinence or vasectomised partner.