A prospective randomized study comparing the clinical effects of a norethisterone and a levonorgestrel containing low dose oestrogen oral contraceptive pills

Abstract

The two types of low dose oral contraceptives one containing levonorgestrel the other containing norethisterone have been compared in a randomized prospective study. We have found that cycle control was much poorer with the norethisterone pill and would therefore recommend that if the norethisterone-containing pill needs to be prescribed then either the 1 mg or the 'synphasic' preparation should be considered.

PIP: In Australia, providers with the Family Planning Association of Victoria randomly enrolled 240 women 15-33 years old, into either a group receiving the combined oral contraceptive (OC) with a progestin of 500 mg norethisterone (Brevinor) or a group receiving the OC with 150 mcg levonorgestrel (Nordette 30) to compare the 2 OCs' clinical effects. They were able to follow-up on only 140 women (48 for 15 cycles and 92 for 1-12 cycles). During the cycles, norethisterone users were more likely to experience breakthrough bleeding than levonorgestrel users (78.3% vs. 50%; p 0.001). Breakthrough bleeding was more common in norethisterone users during the 1st 2 cycles than in levonorgestrel users (68.3% vs. 36.2%; p 0.001). It occurred relatively equally in both groups beyond 2 cycles (11.7% and 11.25%, respectively), however. Breast tenderness occurred somewhat more often in levonorgestrel users than in norethisterone users, but the difference was not significant (67.5% vs. 55%). 33% of norethisterone users discontinued Brevinor due to breakthrough bleeding. If family planning providers have to prescribe a norethisterone-containing OC, they should consider prescribing either the 1 mg norethisterone OC (Brevinor 1) or the Synphasic preparation (0.5 and 1 mg norethisterone combination).