Oral contraception: properties and side-effects of COCs and POPs

Combined oral contraceptives In the UK combined oral contraceptives (COCs), containing both oestrogen and progestogen, are the most popular method of contraception for women under age 30. The most common oestrogen used is ethinyl estradiol (EE), in doses between 20 and 35μg. Progestogens are classified according to their steroid structure and the timing of their introduction on to the market. The progestogen-dominant COCs contain the firstand second-generation progestogens norethisterone and levonorgestrel. These are derived from testosterone and tend to exhibit androgenic actions, counterbalancing the oestrogenic activity. The third-generation progestogens desogestrel and gestodene have neutral androgenic or oestrogenic actions; norgestimate (the COC Cilest) acts mostly, but not exclusively, through conversion to levonorgestrel. Drospirenone (the COC Yasmin) differs from other progestogens in COCs: it has very mild diuretic properties due to antimineralocorticoid activity. This may help to oppose the saltand fluid-retaining effects of EE and so reduce symptoms of fluid retention. Drospirenone is also an antiandrogen, so the combination may be an alternative to cyproterone acetate for conditions such as polycystic ovarian syndrome (PCOS). Dienogest is a progestogen with antiandrogenic activity of approximately one-third of that of cyproterone acetate. It is DRUG REVIEW n