Female subjects of childbearing potential must be using a medically accepted means of contraception as defined by one of the following: a) A barrier method of contraception. A barrier method of contraception is a physical barrier designed to prevent pregnancy, i.e., contraceptive foam or suppositories, spermicides, condoms, or diaphragm. b)Oral contraceptives, estrogen/progesterone-based or progesterone based. Women of childbearing potential also must have a negative serum beta-HCG at prestudy.