Overview of progestogen-only contraceptive pills

Progestogen-only contraceptive pills (POPs) contain one of the following:

• levonorgestrel (eg Microlut) or norethisterone (eg Noriday)—these work by thickening cervical mucus, and suppressing ovulation in around 60% of cycles.
• drospirenone (eg Slinda)—provides consistent suppression of ovulation.

POPs are an option for a person who wishes to use an oral method of contraception and has a contraindication to estrogen in combined oral contraception, or a preference to avoid estrogen (eg those wishing to avoid the small increase in thromboembolic risk).

Evidence to guide choice of the type of progestogen-only pill is lacking.

POPs containing levonorgestrel or norethisterone are less effective in people younger than 25 years than in older people; younger people have higher background fertility. Use of these POPs is also limited by a narrow dosing window—the maximum interval between pills is 27 hours. The drospirenone POP has a maximum dosing interval of 48 hours (equivalent to that of combined oral contraceptives); this longer interval may be more convenient, particularly if life stage (eg breastfeeding) or other factors affect adherence to dose timing. The drospirenone POP appears to be helpful for dysmenorrhoea, and to increase the likelihood of amenorrhoea compared to levonorgestrel and norethisterone POPs. At the time of writing, the drospirenone POP is not listed on the Pharmaceutical Benefits Scheme (PBS); see the PBS website for current information.