title: A clinical comparison of two triphasic oral contraceptives with levonorgestrel or norethindrone: a prospective, randomized, single-blind study.
abstract: Menstrual bleeding patterns were investigated in young women taking either a levonorgestrel triphasic, Triquilar, or a norethindrone triphasic, Ortho 7/7/7, two commonly prescribed low-dose oral contraceptives. The levonorgestrel triphasic contains ethinyl estradiol (EE) 30 micrograms + levonorgestrel (LNG) 50 micrograms for the first six days, EE 40 micrograms + LNG 75 micrograms for the following five days, and EE 30 micrograms + LNG 125 micrograms for the last ten days. The norethindrone triphasic contains EE 35 micrograms + norethindrone (NET) 0.5 mg for the first seven days, EE 35 micrograms + NET 0.75 mg for the following seven days and EE 35 micrograms + 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 1-4, 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, compared with the norethindrone triphasic Ortho 7/7/7.
authors.affiliation: Sunnybrook Health Science Centre, Toronto, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Masson
authors.forename: E
authors.initials: E
authors.lastname: Franssen
authors.forename: J R
authors.initials: JR
authors.lastname: Hilditch
authors.forename: M G
authors.initials: MG
authors.lastname: Powell
mesh_terms: D000293:Adolescent; D000328:Adult; D003277:Contraceptives, Oral, Combined / Q000494:pharmacology; D003279:Contraceptives, Oral, Sequential / Q000494:pharmacology*; D004338:Drug Combinations; D004997:Ethinyl Estradiol / Q000494:pharmacology*; D019304:Ethinyl Estradiol-Norgestrel Combination; D005260:Female; D006801:Humans; D008598:Menstruation / Q000187:drug effects; D009640:Norethindrone / Q000494:pharmacology*; D009644:Norgestrel / Q000494:pharmacology*; D011446:Prospective Studies; D016037:Single-Blind Method
chemical_list: D003277:Contraceptives, Oral, Combined; D003279:Contraceptives, Oral, Sequential; D004338:Drug Combinations; C020416:norethindrone acetate, ethinyl estradiol, ferrous fumarate drug combination; D009644:Norgestrel; D004997:Ethinyl Estradiol; D019304:Ethinyl Estradiol-Norgestrel Combination; D009640:Norethindrone