9. Women of childbearing potential must have a negative serum beta-human chorionic gonadotropin (beta-HCG) pregnancy test prior to study enrollment. All volunteers must use an intra-uterine device or hormonal contraception during the entire study period and for 1 month after. Women who are postmenopausal for more than 12 months or who were sterilized more than 3 months ago are not considered to have childbearing potential;