 - Females of childbearing potential must have a negative serum pregnancy test within 7 days prior or at enrolment and be willing to use an effective method of birth control for the duration of the study. Effective methods of birth control are defined as those which result in a low failure rate i.e. pearl-index 1 when used consistently and correctly such as: a hormonal oral, transdermal, or injectable contraceptive agent with a double-barrier method; an implantable contraceptive device with a failure rate less than 1 for at least 3 months prior to enrolment; vasectomized partner 