- Females must be non-pregnant, non-lactating and either be of non-childbearing potential (i.e. sterilized via hysterectomy or bilateral tubal ligation or at least 1 year post-menopausal) or of child bearing potential but practicing a medically acceptable method of birth control from at least 2 weeks prior to screening until 30 days after the last dose of varenicline. Examples of medically acceptable methods for this protocol include barrier (diaphragm or condom) with spermicide, an intrauterine (IUD), oral contraceptives, levonorgestrel implant, or complete abstinence.