Acceptable methods of contraception include: 1) systemic birth control (the same type of birth control for at least 3 months prior to entering the study and continuation of this type of birth control throughout the study); 2) double barrier methods (condom with spermicide or diaphragm with spermicide); 3) intra uterine device; 4) vasectomized partner; or 5) abstinence from sexual intercourse.