This is an updated guideline from the FSRH on POPs. There is little new, but I have summarised the bits I found interesting.
Women can be given 12m worth at the initial visit.
Using POP in people of higher weight
There is no need to use more than one pill, regardless of the patient's weight.
Changing from a COC
If the woman has had 7d of pills in a row, or is in the pill free interval then she can swap to the POP with no additional precautions. If she is in the first week of the pack and has to swap before taking 7d of COC (eg presents with focal migraine), then extra precautions are needed for 48hrs. She may also need emergency contraception if she's had UPSI in the pill free week or later.
Bleeding is most troublesome in the first 3m. At 1 yr, 50% of desogestrel (DSG) containing pill users (eg cerelle / cerazette) will have amenorrhoea or infrequent bleeding. Only 10% of traditional pill users will. This may encourage some women to persevere beyond the 3m point.
There is no evidence that taking more than 1 pill helps. There is also no evidence that switching POP helps, though they acknowledge that this may help some women.
If there is troublesome bleeding, exclude other causes first. Short term tranexamic acid or oestrogen can be tried, but there is no evidence for longer term use.
POP can be used alongside HRT as contraception, but can not be used as the progestogenic component of HRT.
DSG pills may be helpful in dysmenorrhoea.