Dose starts on first day of menstrual cycle taking 1 tablet daily.

For transactivation studies CHO cells stably transfected with hER
-RO-LUC, hER-RO-LUC, hAR-MMTVLUC, hPR-B-MMTV-LUC, hPR-A-MMTV-LUC or hGRMMTV-LUC were used. 5 × 104 cells/well were seeded into a 96-well plate and incubated with compounds (final ethanol content: 1% v/v) for 16 h in medium with 5% charcoal-treated supplemented defined bovine calf serum at 37°C in a humidified atmosphere of air supplemented with 5% CO2. Of the total 250uL incubation volume, 200 uLl was removed, and 50 uL LucLite was added for cell lysis and luciferase measurement. Luciferase activity was measured in a Topcount luminescence counter (Canberra Packard). Relative agonistic activity (RAA) studies were carried out with various concentrations of the standards (1:2:4 dilutions) and compounds of interest. The RAA was determined to Org 2058 (PRA and PRB). Full agonistic curves for PRA, PRB were also determined in the CHO cells described before. The concentrations of the compounds used were 10−5 to 10−12 mol/l with a dilution factor of 3.16. Norethynodrel displayed agonistic activity with respect to PRA with EC50 of 10 nM, and PRB with EC50 of below 1 nM.