6. Females of childbearing potential must have a negative serum or urine beta human chorionic gonadotrophin (beta-hCG) pregnancy test result within 14 days prior to the first dose of study drugs and must agree to use one of the following effective contraception methods during the study and for 30 days following the last dose of study drug. Effective methods of birth control include: --birth control pills, --shots, --implants (placed under the skin by a health care provider) or patches (placed on the skin); --Intrauterine devices (IUDs); --condom or occlusive cap (diaphragm or cervical/vault caps) used with spermicide. Females of non-childbearing potential are those who are postmenopausal greater than 1 year or who have had a bilateral tubal ligation or hysterectomy.