3. Female subjects of childbearing potential must not be pregnant (as confirmed by negative serum βHCG at screening and negative urine pregnancy test at baseline/during the study), must not be lactating and must use a medically acceptable form of contraception during the study and for at least 1 month after discontinuation of study drug. Medically acceptable contraception as defined here is the oral contraceptive pill, surgical sterilization or hormonal intrauterine device in place for at least 3 months. Women who are less than 2 years post-menopausal are considered to be of childbearing potential.