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Progestogen-only pills (POPs), Noriday (norethisterone) and Cerazette (desogestrel), are dispensed from community pharmacies in Ireland. While the contraceptive prescribing trends data available from a publication by O’Mahony et al in the British Journal of Clinical Pharmacology is from 2008-2013, it suggests that POP is the second most frequently used type of contraception in Ireland, after combined hormonal contraception (CHC). It is considered suitable to prescribe POP for up to one year at a time, according to the Faculty of Sexual and Reproductive Health (FSRH).
POP contains a synthetic progesterone, which has some of the same properties as progesterone. The most likely mechanism of action is different for POP containing norethisterone compared to POP containing desogestrel. The main mechanisms of action of norethisterone are changing the viscosity of the cervical mucus, thinning the endometrium and reducing tubal motility. By contrast, desogestrel works primarily by inhibiting ovulation. If used ‘perfectly’, POP has a very low rate of failure and prevents pregnancy more than 99 per cent of the time. However, the rate of unplanned pregnancies which result from typical use of POP is estimated at nine per cent.
All POPs should be taken at the same time every day for optimal effect. Due to norethisterone’s mechanism of action, it is considered to be ‘missed’ if taken three or more hours late, whereas desogestrel POP is not considered to be ‘missed’ unless it is taken 12 or more hours late.
Similar to CHC, there is a quick return to fertility upon stopping POP. There is only limited evidence to support some non-contraceptive benefits of POP, such as reduction in heavy menstrual bleeding and reduced dysmenorrhea. However, compared to CHC, the POP has the advantage of having less contraindications and being safe to use in many circumstances.
According to the UK Medical Eligibility Criteria (UKMEC) guidelines, POPs are safe to use in most patients requiring contraception from menarche to age 55 years. The only condition in which POP is considered unsuitable is a patient with current breast cancer, and the advice is for contraception to be discussed with the oncologist. Other conditions in which the risk likely outweighs the benefit are past history of breast cancer, severe decompensated cirrhosis, liver tumours, history of stroke or ischaemic heart disease while on POP. There are a number of scenarios in which CHC use may carry some risks, but POP can be safely used — these include use in postpartum and breastfeeding women, use in smokers, use in obese individuals or in individuals with multiple risk factors for cardiovascular disease. POP is also generally considered safe in those who are at increased risk of venous thromboembolism and in those who have migraine with aura, which is a risk for the development of arterial thromboembolism.
The main counselling points for any patient receiving POP are:
| Pharmacist advice | Further information | |
| 1. Indication | Primarily used as contraceptive. Active immediately if started from days one to five of a natural menstrual cycle. | POP can also be started at any other time of the cycle, with the advice to use an additional contraceptive method for two days as long as the prescriber can be reasonably certain that the patient is not pregnant. |
| 2. Posology of use | Explain the correct way to use POP, i.e., by taking at the same time every day. | |
| 3. Missed pills | Explain the concept of missed doses — for traditional POP (norethisterone, Noriday), any dose taken three or more hours late must be treated as a ‘missed dose’. With desogestrel (Cerazette), a pill is considered to be missed if it is taken 12 or more hours late. Patients should also be made aware that severe vomiting or diarrhoea could affect contraceptive efficacy of the POP and bouts of vomiting/diarrhoea should be treated similarly to missed pills. | Emergency contraception may be required if one or more doses are missed and unprotected sexual intercourse occurs between the time the pill was missed and 48 hours post resumption of correct pill-taking; patient should be encouraged to speak to their pharmacist if this happens. |
| 4. Choice of emergency contraception for POP users | If a patient has missed a dose of their POP, emergency contraception (EC) may be indicated. The Cu-IUD is the most effective method of EC. Levonorgestrel is a progestogen, an oral formulation and can be used by patients who are taking POP. POP can be restarted immediately with levonorgestrel. Refer to POP SmPC for advice on contraindications, recommencement and information on additional contraceptive method requirements. | Ulipristal acetate is a progesterone receptor modulator and taking POP in the seven days prior or the five days after ulipristal acetate may affect how well ulipristal acetate works. Therefore, POP should not be restarted for five days post ulipristal acetate and then requires a number of days until it is effective as a contraceptive again as per the Summary of Product Characteristics (generally two days for the POP). Refer to POP SmPC for advice on contraindications, recommencement and information on additional contraceptive method requirements. |
| 5. Side-effects | Side-effects can occur. One of the main reported side-effects that patients should be made aware of, is unpredictable bleeding. It has been reported that bleeding while on POP varies considerably with 40 per cent having a ‘normal’ frequency of bleeding/spotting (approximately once per month), 20-30 per cent having no bleeding at all, 30 per cent having infrequent bleeding and <10 per cent having frequent or prolonged bleeding. | It is worth noting that even though mood change, headache, acne and weight gain may be listed on the patient information leaflet as a side-effect with POP, the FSRH have found that there is not enough evidence to state that any of these are side-effects caused by the POP. |
| 6. Serious adverse effects | There are very few serious adverse effects with POP. The only condition which POP users have a slightly increased risk of when compared to never users, is breast cancer. Any breast changes should be reviewed medically as soon as they are noticed. | Patients can be reassured that adverse effects are incredibly rare and can generally be managed if medical help is sought in a timely manner. |
| 7. Interactions | Patients should be informed that there can be drug-drug interactions which affect POP. If any new medicine is started, they should inform the prescriber and dispensing pharmacist that they are taking POP so that an interaction check can be carried out. | Enzyme inducing drugs can reduce the effectiveness of POP and an alternative form of contraception may be required. The other main interaction to be aware of is with emergency contraception (see point six). |
“The only condition in which POP is considered unsuitable is a patient with current breast cancer, and the advice is for contraception to be discussed with the oncologist.”References available on request. The final article in this CPD series on contraception will focus on emergency contraception.
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