A RANDOMIZED TRIAL OF 3 ORAL-CONTRACEPTIVES - COMPARISON OF BLEEDING PATTERNS BY CONTRACEPTIVE TYPES AND STEROID-LEVELS

OBJECTIVE: Our purpose was to determine the relationship between bioav ailability of contraceptive steroids and bleeding patterns. STUDY DESI GN: A randomized clinical trial evaluated 192 women on 50 mug of ethin yl estradiol and 1.0 mg of norethindrone (OC1), 35 mug ethinyl estradi ol and 1.0 mg of norethindrone (OC2), and 35 mug ethinyl estradiol and 0.5 mg norethindrone (OC3) over nine cycles. RESULTS: Intermenstrual bleeding rates were higher for OC3 when compared with OC1 (p = 0.01). The number of intermenstrual bleeding days was highest for OC3 (p = 0. 001) and higher for OC2 when compared with OC1 (p < 0.006). The onset of withdrawal bleeding occurred faster in OC3 patients (p < 0.02). Bio availability of both contraceptive steroids as measured by baseline va lues and 1-hour slopes did not correlate with bleeding patterns at 3, 6, and 9 months of use. CONCLUSION: These data suggest that difference s in biologic responses associated with pill use cannot be explained s olely on the basis of these particular hormone measurements.