Abstract

There are now six oral contraceptive (OC) preparations available in which the doses of the constituents vary through the cycle. All such “phased” formulations contain an oestrogen and a progestogen. In one (BiNovum), the cycle comprises two formulations (biphasic) with a single pill change after the 7th day. The remainder (Logynon, Logynon ED, Synphase, Trinordiol and TriNovum) are all triphasic with changes in formulation on or around the 6th and 12th days. In the original triphasic preparations (Logynon or Trinordiol)¹ the progestogen content increases through the cycle: for the first 6 days each pill contains 50μg levonorgestrel, for the next 5 days 75μg, and in the last 10 days 125μg. This is also the pattern for TriNovum but norethisterone replaces levonorgestrel.