| Methods |
Randomized controlled trial with blinding of the outcome assessor. The method of randomization, the use of allocation concealment and the method of blinding are not described. Communication with the author revealed no extra information. |
| Participants |
At 4 sites in Canada, 469 women were randomized to one of the pills. However, only 391 women were admitted to the study and used the pills for at least one month. 222 women did not use OC pills at least 90 days before the study, and 247 women did use pills before the study. Inclusion criteria were healthy women aged 15 to 35 years who had a history of regular menses for two months prior to admission. Exclusion criteria were contraindications to oral contraceptives. |
| Interventions |
Triphasic levonorgestrel/ethinylestradiol (50‐75‐125 μg LNG and 30‐40‐30 μg EE in a 6/5/10 days regimen, N=119) [Triphasil] versus
triphasic norethindrone/ethinylestradiol (500‐750‐1000 μg NET and 35 μg EE in a 7/7/7 days regimen, N=117)) [Ortho 7/7/7] versus
biphasic norethindrone/ethinylestradiol (500‐1000 μg NET and 35 μg ethinylestradiol in a 10/11 days regimen, N=116) [Ortho 10/11] versus
monophasic norethindrone acetate/ethinyl estradiol (1500 μg NETA and 30 μg EE, N=117) [Loestrin]. In the pre‐study user group, 16 participants already used Triphasil, 5 Loestrin, 8 Ortho 10/11 and 8 Ortho 7/7/7. |
| Outcomes |
Primary outcomes measures are: side effects; cycle control; continuation, discontinuation rates and reason for discontinuation. Use of daily diary method to collect data on cycle control and side effects. Breakthrough bleeding was defined as free flow, much like menses occurring during the 21 days of active medication and requiring sanitary protection; and spotting as bleeding during the active medication, which is limited to minor staining, whether or not sanitary protection was used. |
| Notes |
The report provides an a priori hypothesis and an adequate sample size calculation. Study duration: 6 cycles. 49 women in the monophasic group, 35 women in the biphasic group, 46 women in the levonorgestrel triphasic group and 39 women in the norethindrone triphasic group discontinued early. The reasons for discontinuation are partially described. The report does not describe the number of women lost to follow up or withdrawn because of protocol violations. Analysis not according to intention‐to‐treat principle. 78 women who were randomized but did not take the oral contraceptives for at least one cycle were excluded from the analysis. Breakthrough bleeding includes all intermenstrual bleeding except continued menstrual flow in this review. The trial was sponsored by the manufacturer of the monophasic norethindrone acetate/ethinylestradiol pill (Parke‐Davis). |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Allocation concealment (selection bias) |
Unclear risk |
No information |
