 13. Female patients who are pregnant or lactating, or adults of childbearing potential who are not practicing a medically acceptable method of birth control. Female patients must use barrier contraception in addition to condom use in their partner. If oral contraception is used, the patient must have been practicing this method for at least two months prior to enrollment and must agree to continue the oral contraceptive throughout the course of the study, and for three months after the study has ended. Male patients who are sexually active are required to use condoms during the study and for three months afterward. 