| Methods |
Double‐blind, randomized controlled trial. The method of randomization and the method of blinding are not described. Communication with the author indicated randomization in a 3:2 ratio in blocks of five, and double‐blinding by identical pills and packages. The method of randomizing the blocks of five is unclear. |
| Participants |
1277 women at 8 sites. Inclusion criteria were women aged 18 to 35 years with a history of regular menstrual cycles (28 + 3 days) for 2 consecutive cycles immediately before study entry. Exclusion criteria were contraindications to oral contraceptives and use of oral contraceptives within 2 months before enrollment. Limited information on baseline demographics. |
| Interventions |
'Estrophasic' norethindrone acetate/ethinylestradiol (1000 μg NETA and 20‐30‐35 μg EE in a 5/7/9 days regimen, N=769) [Estrostep] versus
monophasic norethindrone acetate/ethinylestradiol (1500 μg NETA and 30 μg EE for 21 days, N=508) [Loestrin 1.5/30]. |
| Outcomes |
Primary outcome measures are: efficacy; cycle control; side effects; discontinuation due to side effects. Use of special diaries to collect data on cycle control, side effects, pill‐intake and concomitant medication. Breakthrough bleeding was defined as vaginal bleeding during the medication‐taking period that was not a continuation of menstrual flow and that necessitated pad or tampon protection. |
| Notes |
Report does not provide an a priori hypothesis or a sample size or power calculation. Study duration: 6 cycles. Number of and reasons for discontinuation are not described except discontinuation due to side effects. Unclear whether the analysis was according to intention‐to‐treat principle. Random assignment in a 2:1 ratio. However, 769 women received the 'estrophasic' preparation and 508 the monophasic preparation. Communication with the author indicated a 3:2 allocation ratio. We only included study 1 in this review. Study number 2 compares the 'estrophasic' combination with a triphasic combination in terms of metabolic outcomes. The trial was sponsored by the manufacturer of the studied monophasic and estrophasic norethindrone acetate/ethinylestradiol pills (Parke‐Davis). |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| Allocation concealment (selection bias) |
Low risk |
Not described in report. Communication with the author indicated allocation concealment by numbered pharmacy packages. |
