A CLINICAL COMPARISON OF 2 TRIPHASIC ORAL-CONTRACEPTIVES WITH LEVONORGESTREL OR NORETHINDRONE - A PROSPECTIVE, RANDOMIZED, SINGLE-BLIND STUDY

Menstrual bleeding patterns were investigated in young women taking either a levonorgestrel triphasic, Triquilar(R), or a norethindrone triphasic, Ortho 7/7/7(R), two commonly prescribed low-dose oral contraceptives. The levonorgestrel triphasic contains ethinyl estradiol (EE) 30 mug + levonorgestrel (LNG) 50 mug for the first six days, EE 40 mug + LNG 75 mug for the following five days, and EE 30 mug + LNG 125 mug for the last ten days. The norethindrone triphasic contains EE 35 mug + norethindrone (NET) 0.5 mg for the first seven days, EE 35 mug + NET 0.75 mg for the following seven days and EE 35 mug + NET 1.0 mg for the last seven days. Three hundred women from 16 to 25 years of age were randomized to the levonorgestrel triphasic (n = 150) or the norethindrone triphasic (n = 150) groups. Assessments were made from daily diary cards and from bimonthly investigator interviews over 6 pill cycles. The results showed a higher incidence of intermenstrual bleeding (breakthrough bleeding and/or spotting) in the norethindrone triphasic group (NET group) than in the levonorgestrel triphasic group(LNG group): 44.9% of patients (66/147) randomized to the LNG group reported intermenstrual bleeding one or more times during the study compared with 61.9% (91/147) randomized to the NET group (p = 0.0036). Furthermore, in subjects who did not miss any pills, the proportion of patients with intermenstrual bleeding in each cycle was significantly greater (p < 0.02, cycles 14, 6; p > 0.05, cycle 5) 'and was experienced for more days per cycle (p < 0.05, cycle 1) and for more cycles per patient (p < 0.05, 5 cycles) in the NET group compared with the LNG group. Intermenstrual bleeding was also less frequently observed in the LNG group than in the NET group in patients who missed pills (p < 0.05, cycles 3, 5 and 6). In addition, early withdrawal bleeding occurred more often in the NET group than in the LNG group (p < 0.05, cycles 1, 3 and 4). The incidence of amenorrhea was similar in both groups. These results demonstrate a significantly lower incidence of intermenstrual bleeding and therefore better cycle control with the levonorgestrel triphasic Triquilar(R), compared with the norethindrone triphasic Ortho 7/7/7(R).