A method for contraception includes administering to a female daily, during a time period of 21 successive days, an oral combination drug formulation of norethindrone acetate and ethinyl estradiol (EE), wherein the drug formulation is administered in a biphasic dosing regimen comprising a 14 day phase and a 7 day phase, wherein doses of each of the norethindrone acetate and EE in the second phase of the regimen increase by a predefined dose increment as compared to the corresponding doses of the norethindrone acetate and EE administered during the first phase of the regimen, wherein the norethindrone acetate dose in the first phase is 1000 mcg and in the second phase is 1500 mcg, wherein the EE dose in the first phase is 20 mcg and in the second phase is 30 mcg, and wherein the biphasic dosing regimen is followed by 7 days without norethindrone acetate and EE administration.
