RESUMO
BACKGROUND: The efficacy of contraceptives is affected by its route and ease of administration. Herein, both pharmacokinetics and pharmacodynamics of the once-a-month combined injectable contraceptive medroxyprogesterone acetate (MPA) plus estradiol cypionate (E(2)-Cyp) were compared after intramuscular (IM) or subcutaneous (SC) injection in women of reproductive age. STUDY DESIGN: Thirty women were randomly assigned to the SC (n=15) or IM (n=15) route of MPA 25 mg+E(2)-Cyp 5 mg administration. Serum samples were obtained daily for 7 days and then three times a week for 40 days in order to quantify E(2), progesterone and MPA. In addition, three ultrasounds were performed on each subject to determine follicular development, and a daily record of the bleeding pattern and side effects was maintained. RESULTS: A comparative analysis showed that the main pharmacokinetic (peak serum concentration, peak serum time, area under the serum concentration vs. time curve, absorption half-life and elimination half-life) and pharmacodynamic parameters, such as follicular development and ovulation, were similar in the SC vs. IM groups. Complete suppression in ovarian function was present in all women. The bleeding patterns and side effects were similar in both groups. CONCLUSIONS: The results presented herein demonstrate that the injection of 25 mg of MPA plus 5 mg of E(2)-Cyp has similar efficacy and safety with either the SC or IM route of administration. The SC option can be considered a viable self-administered contraceptive option that might increase women's compliance to contraceptive use.