- Women of childbearing potential may participate if they are not pregnant or breast feeding, and if they agree to use one of the following methods of contraception throughout the study: abstinence, intrauterine device, condom and foam, diaphragm and spermicide, vasectomy and spermicide, tubal ligation and spermicide, oral contraceptives and barrier method. Women using oral contraceptives must have been on a stable dosing regimen for at least 6 months prior to study entry and must agree to continue on that same dosing regimen throughout all phases of the study.