6. Female patients must be non-lactating and must either be at least two years post-menopausal, or be using adequate mechanical contraceptive precautions (i.e. intrauterine device, diaphragm with spermicide, condom with spermicide), or be surgically sterilized (i.e. bilateral tubal ligation, bilateral oophorectomy). Female patients who have undergone a hysterectomy are eligible for participation in the study. Female patients (except for those patients who have undergone a hysterectomy or a bilateral oophorectomy) are eligible only if they have a negative pregnancy test throughout the study period. Patients on oral contraceptives or an hormonal implant will be excluded.