PHARMARCOKINETICS OF ONCE-A-MONTH INJECTABLE CONTRACEPTIVES

The addition of a short- or medium-acting estrogen ester to the long-a cting progestins depot-medroxygrogesterone acetate (DMPA) and norethis terone enanthate (NET-EN) to produce ''combined'' injectable formulati ons has proved a successful strategy in the development of once-a-mont h injectable contraceptives. Recent clinical pharmacokinetic studies u ndertaken on once-a-month injectable contraceptives in various WHO Col laborating Centers have guided the selection of the estrogen-progestog en combinations, ratios and dose schedules. At least three combined on ce-a-month injectable preparations exhibit acceptable pharmacokinetic and pharmacodynamic profiles; however, further improvement in the desi gn of optimal estrogen/progestin injectables are expected during this decade