The progesterone-only pill

Abstract

The progesterone-only pill is a popular and effective contraceptive method. It is particularly useful when either an oral method of contraception is preferred or there are contraindications to the combined pill. It is taken daily without a pill-free interval, and works mainly by increasing the cervical mucus. Desogestrel also inhibits ovulation. The progesterone-only pill is useful for those needing a reliable form of contraception within a short period, as it is effective after 48 hours when ‘quick started’. This article reviews current guidelines and answers some common clinical queries.

The GP curriculum and the progesterone only pill

Clinical module 3.08: Sexual health states that GPs should:

Appreciate the definition of sexual health as being about the ‘enjoyment of the sexual activity you want without causing yourself or anyone else suffering or physical or mental harm. It is also about contraception and avoiding infections’

Demonstrate a working knowledge of contraception: effectiveness rates, risks, benefits and appropriate selection of patients for all methods. Refer to the UK Medical Eligibility Criteria for contraceptive use

Know when urgent intervention is needed in sexual health and, if necessary, refer appropriately, e.g. in the provision of emergency contraception

Introduction

The progesterone-only pill (POP) or ‘minipill’ solely contains progesterone, whereas the combined oral pill (COP) contains oestrogen and progesterone. The two main classes of POP are ‘traditional’ or ‘older’ POPs (Norethisterone and levonorgestrel type) and the ‘newer’ or desogestrel POP. There are three POPs available in the UK:

350 micrograms norethisterone (Noriday®, Micronor®)

30 micrograms levenorgestrel (Levogeston®, Norgeston®)

75 microgram desogestrel (Cerazette®, Cerelle®, Feanolla®, Aizea® and other branded generic products) (Joint Formulary Committee, 2018)

How do POPs work?

POPs work mainly by increasing the volume and viscosity of cervical mucus in the upper genital tract making it impenetrable to sperm. This effect is achieved after approximately 48 hours of pill-taking. To work reliably, the pill must be taken regularly, as the effect on cervical mucus lasts less than 24 hours (McCann and Potter, 1994).

The desogestrel POP gives additional protection by suppressing ovulation in about 97% of cycles. This method of action applies much less to other types of POP, for example only in 60% of cycles when using the levonorgestrel POP (Faculty of Sexual and Reproductive Healthcare (FSRH), 2015).

The POP is also thought to induce changes that hinder endometrial egg implantation and reduce ciliary activity in the fallopian tubes, therefore slowing the passage of an egg. The POP can also suppress the mid-cycle peaks of luteinising hormone and follicle-stimulating hormone, which normally initiate ovulation and the conversion of the mature follicle into the corpus luteum (The National Institute for Health and Care Excellence (NICE), 2016).

Who can start the POP?

The POP is suitable for a wide range of patients and can be prescribed until the menopause or 55 years of age, providing there are no medical conditions restricting use. Contraindications include current or past ischemic heart disease or stroke, current or past breast cancer, hepatocellular adenoma or malignant liver tumours. Contraindications are detailed in Table 1 (FSRH, 2016).

Table 1.

UKMEC3 and UKMEC 4 criteria for POP.

Condition	UKMEC Category
Current and history of ischaemic heart disease	2 (I)/3 (C)
Stroke (history of cerebrovascular accident or transient ischemic attack)	2 (I)/3 (C)
Past breast cancer	3
Severe (decompensated) liver cirrhosis	3
Hepatocellular adenoma	3
Malignant hepatocellular carcinoma	3
Current breast cancer	4

(I): initiation; (C): continuation.

Category 1: A condition for which there is no restriction for the use of the method

Category 2: A condition where the advantages of using the method generally outweigh the theoretical or proven risks

Category 3: A condition where the theoretical or proven risks usually outweigh the advantages of using the method. The provision of a method requires expert clinical judgement and/or referral to a specialist contraceptive provider, since use of the method is not usually recommended unless other more appropriate methods are not available or not acceptable

Category 4: A condition which represents an unacceptable health risk if the method is used

Adapted from FSRH (2016).

It is important to check past and current medication use, as cytochrome P450 enzyme-inducing drugs decrease the efficacy of the POP by increasing the rate at which progesterone is metabolised (FSRH, 2015). These include antiepileptics (e.g. carbamazepine, phenytoin, phenobarbital, topiramate), antibiotics (e.g. rifampicin, rifabutin), antiretrovirals (e.g. efavirenz, nevirapin), herbal preparations (e.g. St. John’s Wort) and others such as modafinil. A comprehensive list can be found in the FSRH’s Clinical Guidance: Drug Interactions with Hormonal Contraception (FSRH, 2018), the British National Formulary (BNF) (Joint Formulary Committee, 2018) and the online BNF interaction checker: https://bnf.nice.org.uk/interaction/.

These drugs may induce cytochrome P450 enzymes within 2 days of taking them, and the effects are typically maximal within a week. The enzymes usually return to their previous level of activity within 4 weeks of cessation (FSRH, 2018).

Women starting enzyme-inducing drugs should be warned of potential interactions, and then offered an alternative method of contraception unaffected by such drugs (e.g. intrauterine contraception or progesterone-only injectables). As per the FSRH guidelines, short-term use of enzyme-inducing drugs can be managed more flexibly, and if enzyme-inducing drugs are used for 2 months or less, women may be given the option of continuing with their method and using barrier methods such as condoms during treatment and for 28 days afterwards (FSRH, 2015). Similarly, women who have stopped enzyme-inducing drugs recently and would like to start the POP should continue using barrier methods for 28 days after the last dose of the enzyme-inducing drug (FSRH, 2015).

Starting the POP

Women can start the POP at any time in their cycle, providing they are not pregnant.

If started within 5 days of the last menstrual period, additional contraceptive methods are unnecessary, and it is considered effective immediately. However, if started after day 5 of the cycle (i.e. ‘quick started’- off label use) additional barrier methods or abstinence from sex for 48 hours is advisable (FSRH, 2017a; NICE, 2016). Starting the POP in a variety of circumstances is now considered and a summary listed in Table 2.

Table 2.

FSRH advice on starting the POP.

Circumstance	Timing of initiation	Additional precaution	Clarification
Women with menstrual cycles	Days 1–5	No	Review that menstrual cycle was typical in terms of timing, heaviness and duration
	After day 5	Yes (for 48 hours)	If in doubt take pregnancy test
Women who are amenorrhoeic	At any time	Yes (for 48 hours)	Exclude pregnancy prior to starting. Consider EC and advise pregnancy test 3 weeks post UPSI
Postpartum (breastfeeding and non-breastfeeding)	Up to day 21 post-partum	No additional precautions required	Contraception is not required before day 21 postpartum
	Post day 21 post-partum	Yes (for 48 hours) unless using LAM
Post first- or second- trimester abortion	Days 1–5	No	Hormonal contraception can be initiated after the first part of a medical abortion. Ovulation is thought to occur as early as Day 8 following medical abortion
	At any other time	Yes (for 48 hours)	Consider need for EC and pregnancy test 3 weeks post UPSI
Following oral EC administration
LNG-EC	Start immediately	Yes (for 48 hours)	Advise pregnancy test 3 weeks after UPSI
UPA-EC	Start 5 days after	Yes (for 48 hours)	Advise pregnancy test 3 weeks after UPSI

EC: emergency contraception; LAM: Lactational Amenorrhoeal Method; UPSI: unprotected sexual intercourse; LNG: levonorgestrel; UPA: Ulipistal acetate.

Adapted from FSRH (2015).

Changing between POPs

Women who would like to change between POPs can be advised that a direct switch is possible and no additional methods are needed (NICE, 2016). It is important to assess compliance with the pill prior to switching and to confirm there is no risk of pregnancy.

Changing from the COP to the POP

If switched in the first week of the COP cycle (days 1–7), women should be advised to use additional barrier methods or abstain from sex for 48 hours

When starting a POP in the second or third week of the COP cycle, or during the pill-free interval, no additional precautions are needed

In a case of unprotected sexual intercourse (UPSI) in the pill-free interval, or the first week of the COP cycle, the COP should be continued for 7 consecutive days before switching to the POP. If the COP cannot be continued, the POP can be started immediately with the use of emergency contraception (EC), and a pregnancy test performed 3 weeks post UPSI (NICE, 2016)

Emergency contraception and the POP

If a woman has had UPSI and does not wish to become pregnant, the risk of pregnancy depends on the fertility of both of the partners, the timing and number of episodes of UPSI, the cycle length and variability, and contraception use (FSRH, 2017b). The copper intrauterine device (Cu-IUD) is the most effective form of EC (overall pregnancy rate of <0.1) and is the only form of EC that is effective post ovulation (FSRH, 2017b). Oral EC such as ulipristal acetate (UPA-EC, (Ella-One ®)) or levenorgestrel (LNG-EC (Levonelle®)) can be offered, but the efficacy of these methods depends on both the timing of the UPSI in the cycle and when the EC is taken. Women should be advised that oral EC is not thought to be effective post ovulation. UPA-EC is effective pre-ovulation if taken within 120 hours of UPSI with a pregnancy rate of 1–2%. LNG-EC may be given pre-ovulation, up to 72 hours post UPSI. It is slightly less effective and has a pregnancy rate of 0.6–2.6% (FSRH, 2017b).

For further guidance consult the FSRH’s Guideline Emergency Contraception and flowcharts below (Figs 1 and 2). An EC calculator is also available at https://sxt.org.uk/ec.

Figure 1.

Decision-making algorithm for EC: Cu-IUD vs oral EC.

Figure 2.

Decision-making algorithm for oral EC: LNG-EC vs UPA-EC.

If oral EC is given, timing of commencement of the POP after EC varies, as there is a risk that progesterone reduces the efficacy of UPA-EC (FSRH, 2017b). Therefore, the POP should be started 5 days after taking UPA-EC. In addition, women are recommended to avoid sexual intercourse or to use barrier contraception during this time and for the first 2 days after starting the POP, i.e. 7 days of barrier methods or abstaining from sex from the time UPA-EC was taken (NICE, 2016).

For LNG-EC (Levonelle®), the POP can be started immediately, and barrier contraception or abstaining from sex for 48 hours should be advised. In addition, women should be advised to take a pregnancy test 3 weeks following the UPSI.

Women with amenorrhoea

In women who are amenorrhoeic, the POP can be started at any time if one can be reasonably certain that the woman is not pregnant. Additional contraception or abstaining from sex for 48 hours after starting the POP should be advised. Review the need for EC and advise women to take a pregnancy test 3 weeks after the last UPSI (NICE, 2016).

Women in postpartum period

The POP is safe to use in the postpartum period at any time, and is also suitable for women who are breastfeeding. When started before day 21 postpartum, no additional precautions are required, and it is effective immediately.

Women starting the POP after day 21 postpartum should be advised to abstain from sex or use a barrier method for 48 hours. Consider the need for EC if the woman has had UPSI and advise to take a pregnancy test 3 weeks’ post UPSI. For women switching from the ‘Lactational Amenorrhoea Method’ (which is effective when women are exclusively breastfeeding, have no periods and are up to 6 months postpartum) no additional precautions are needed (NICE, 2016). Of note, the COP can be used from 6 weeks postpartum onwards, regardless of whether women are breastfeeding (UK Medical Eligibility Criteria (UKMEC) 2), provided there are no other contraindications (FSRH, 2016).

Women with recent termination of pregnancy or miscarriage

Following termination or miscarriage with a gestational age less than 24 weeks, the POP can be started on the day or within 5 days of miscarriage, surgical termination or first part of medical termination, and no additional contraception is required.

If 5 days or more after miscarriage or termination, the woman should be advised to abstain from sex or use barrier methods for 48 hours. In cases of UPSI, review the need for EC and pregnancy test 3 weeks following UPSI (NICE, 2016).

How effective is the POP?

POPs are thought to be over 99% effective with ‘perfect’ use (when the method is always used correctly) and approximately 91% effective with ‘typical’ use. That means that 9 of 100 women using the POP will get pregnant in a year. The desogestrel POP may be more effective than traditional POPs, due to its suppressive effect on ovulation. Desogestrel also has a longer missed pill window period of 12 hours in which it can be taken, versus 3 hours for the traditional pills, and there may be fewer ‘missed pills’.

Of note, desogestrel is a pro-drug and metabolised to the active progestogen etonogestrel in the liver. Etonogestrel is also released by the more effective sub-dermal implant, at a dose equivalent to three desogestrel POPs per week. A trial of desogestrel POP may be considered if women are concerned about the side effects of the sub-dermal implant (Gallagher et al., 2014), but women should be informed that it is not a reliable predictor of future bleeding pattern and side effects. It should not be used routinely in this way, as a trial may simply delay use of the appropriate long-acting reversible form of contraception.

There is insufficient evidence to compare efficacy, acceptability and continuation rates for progesterone-only methods, either between different progesterone-only methods or with combined oral contraceptive methods (Grimes et al., 2013).

There have been concerns about patients’ weight and its influence on the effectiveness of the POP. FSRH advises that there is no increased risk of pregnancy in POP users with a heavier body weight or a higher body mass index (BMI). Evidence is lacking to recommend more than one pill per day in women who are heavy or overweight (FSRH, 2015).

Absorption of the pill may be affected by vomiting and diarrhoea. Women should be counselled that any vomiting within 2 hours of taking the pill, requires another pill to be taken as soon as possible. If the subsequent pill is missed, additional precautions may be needed for 48 hours after resuming the pill. If a patient has severe, watery diarrhoea for 24 hours, the same rules apply and additional precautions may be needed (Family Planning Association, 2017).

The UKMEC states that bariatric surgical procedures leading to malabsorption may decrease the efficacy of oral contraception. In addition, efficacy may be further affected by post-operative complications such as chronic diarrhoea and vomiting.

There is some conflicting evidence that this may occur in women after jejuno-ileal bypass. However, other types of bariatric surgery (e.g. adjustable gastric bands or biliopancreatic diversions) lead to no observable substantial decrease in effectiveness (FSRH, 2016).

Timing of the pill

To maximise efficacy and aid adherence, the POP should be taken at the same time every day, at a time suited to the woman’s lifestyle. Alarms or medication apps may be used to aid compliance. A subdermal implant or intrauterine contraceptive method may be a suitable alternative for women regularly forgetting to take their pills.

Missed pills

The missed pill window for traditional POPs is 3 hours and 12 hours for desogestrel POP (McCann and Potter, 1994). This means that if a woman has forgotten to take the POP, a traditional POP can still be taken with contraceptive efficacy for up to 3 hours after the normal time of taking, and a desogestrel POP for up to 12 hours after. If taken later than 3 or 12 hours respectively, then consider these events as missed pill episodes.

Women should be warned that any UPSI following the missed pill window may result in pregnancy and EC should be sought. See Fig. 3 for further information.

Figure 3.

Advice for women when a POP is late or missed.

Are there other benefits of the POP?

The POP is suitable for many women and has very few contraindications. It may reduce the risk of endometrial cancer, and desogestrel may improve dysmenorrhoea and mid-cycle ovulatory pain (NICE, 2016). Normal fertility returns as soon as the POP is stopped, so it may be useful in women who are planning to start a family in the near future.

What are the side effects of the POP?

Irregular bleeding patterns

The most common side effect is menstrual irregularity. This is also the most common reason to discontinue the POP (FSRH, 2015). Discussion prior to its prescription may help reduce discontinuation rates.

Women may experience prolonged bleeding, breakthrough bleeding or spotting in one or more cycles. The bleeding pattern is influenced by the type of POP, the dose, the circulating estradiol content and the effect of the POP on ovulation. The bleeding patterns are therefore quite variable.

When counselling women, the following can be used as a guide for the desogestrel POP. After 12 months of use, in a 3-month period (E-learning for Healthcare, 2013):

5 in 10 women can expect amenorrhoea or infrequent bleeding

4 in 10 women can expect regular bleeding

1 in 10 women can expect frequent bleeding

With traditional POPs, frequent and irregular bleeding patterns are more typical, and they less commonly cause prolonged bleeding or amenorrhoea. In all women, it is important to remember that although bleeding problems are common, other causes of bleeding should always be considered and investigated where necessary. The most useful initial investigations are screening for sexually transmitted infections (STIs) and ensuring that cervical cytology is up to date.

Skin reactions

Skin reactions are often reported side effects (Joint Formulary Committee, 2018). However, this is not stated in the FSRH and NICE guidelines (FSRH, 2015; NICE, 2016).

Breast tenderness

Some women may notice breast changes and tenderness. Often this is temporary and may settle after a few months, however, if persistently troublesome, consider changing to another POP or to another contraceptive method (NICE, 2016).

Libido

Changes in libido (a reduction for desogestrol POPs; both reduction and increase with traditional POPs) are included in the product characteristics for POPs. However, the multifactorial causes and subjective nature of these symptoms contribute to a paucity of studies investigating libido changes with POPs and no association has yet been clearly demonstrated (FSRH, 2015).

Weight changes

Many women worry about weight gain, and weight fluctuations are very common in women of reproductive age. The FSRH reports no evidence overall that POPs cause weight gain, although one clinical trial did show limited evidence of this effect (FSRH, 2015).

What are the risks of the POP?

Cardiovascular disease

There are few studies that have reviewed the risk of venous thromboembolism (VTE) associated with progesterone-only contraception, but so far there is no evidence of an increased risk associated with the POP. There is a risk that norethisterone is partially metabolised to ethinylestradiol, theoretically increasing VTE risk. However, this conversion is unlikely to occur at the 350-microgram doses currently available (FSRH, 2015).

Breast cancer

There are limited studies investigating the risk of breast cancer associated with POP use, but those available have not shown any increased level of risk. Due to the limited number of studies and evidence, the risk cannot be excluded. It is likely to be small and to reduce after stopping the POP (FSRH, 2015).

Depression and mood change

Mood changes and depression are listed as side effects, but evidence of causation is lacking (FSRH, 2015). An association with panic attacks is listed with desogestrel POPs (NICE, 2016), based on 25 reports between 2003 and 2017 on ‘VigiBase’, the World Health Organisations’ Global Individual Case Safety Report (Watson and Harmark, 2018).

Headaches

The limited evidence available does not show an increased risk of headaches or migraine. POPs can be used in women who suffer from migraines with or without aura (UKMEC2) (FSRH, 2015).

Ectopic pregnancy

Although when used correctly the POP is a very effective form of contraception, there is an up to 1 in 10 chance of an ectopic pregnancy with traditional POP use (FSRH, 2015). The desogestrel POPs are less often linked with ectopic pregnancy or follicular cysts compared with traditional POPs, consistent with the suppression of ovulation. A history of ectopic pregnancies or risk factors for ectopic pregnancy should not restrict POP use (FSRH, 2016).

Ovarian cysts

The POP has been linked to persistent ovarian follicles and spontaneously reversible ovarian cysts. It can be used in women with benign ovarian tumours, including cysts (FSRH, 2016).

Return of fertility

After stopping the traditional POP there is no delay in return of fertility. In a study on the ovulation rates with the desogestrel pill, it took an average of 17.2 days to first ovulation (range 7–30 days) (Korver et al., 2005). After stopping POPs, women should be advised to switch immediately to alternative contraceptive methods if they do not wish to become pregnant (FSRH, 2015).

Follow up and continuation of POP

Follow up

NICE recommends prescribing for 3 to 6 months at the first visit with follow up after 10–12 weeks and every 12 months thereafter if there are no side effects (NICE, 2016). The FSRH guidelines differ slightly and have recently changed. They suggest a 12 months’ supply of POP or COP at first visits and follow up appointments tailored to the individual. Less than 12 months could be offered if the woman is thinking about the subdermal implant, has a history of hormonal side effects or would prefer an earlier review. Women should be advised to return if any problems or concerns arise (FSRH, 2015).

At ‘pill check’ appointments, women should be reviewed for any new risk factors or contraindications, changes in medical, drug, family or sexual history and for side effects, pill compliance, missed pill rules and to be reminded of possible drug interactions. Checking blood pressure and BMI is recommended (NICE, 2016), but not necessary according to the FSRH guidelines (FSRH, 2015). Verbal or written advice on long-acting reversible contraceptive methods (i.e. Cu-IUD levenorgestrel intrauterine system, progesterone-only injectables, progestogen-only implant, and combined hormonal vaginal ring) should be offered (FSRH, 2015).

Menopause

In the UK, the average age of menopause is 51 years (NICE, 2017). By the age of 55 years, it is thought that most women will have gone through the menopause and the POP can safely be continued until then if there are no other contraindications.

If a woman older than 50 years is still menstruating, consider the need to review abnormal or changing bleeding patterns. If a woman is still bleeding at 55 years of age, contraception should be continued until they have been amenorrhoeic for a year (FSRH, 2015).

In amenorrhoeic women over 50 years in age, one can review if menopause has occurred by checking serum follicle-stimulating hormone (FSH) levels depending on local guidelines. This needs to be done on two occasions, with an interval of 6 weeks between tests. If both FSH levels are more than 30 IU/L, the POP can be stopped after a further year (NICE, 2016). Of note, the NICE menopause guidelines do not recommend routine testing for menopause; FSH testing should only be considered in women aged 40 to 45 years with menopausal symptoms, including a change in their menstrual cycle, or in women aged under 40 years with suspected menopause (NICE, 2017). In addition, FSH testing is not recommended in women taking the COP or high-dose progesterone, as the blood test may be affected by these treatments (NICE, 2017).

Managing bleeding problems

Bleeding problems are a common side-effect of the POP. However, various conditions can present this way and should be excluded, such as STIs, gynaecological pathologies and pregnancy. It is important to check for any problems with pill adherence, drug interactions or factors that may have impacted drug absorption (e.g. vomiting or diarrhoeal illness). All women should be tested for sexually transmitted diseases (as a minimum, for Chlamydia trachomatis) and pregnancy.

It is important to consider cervical or endometrial polyps, cervical cancer and endometrial cancer, particularly in women over 45 years in age. If appropriate, refer the patient for a pelvic ultrasound scan and/or the 2-week wait pathway (NICE, 2016).

Consider speculum and pelvic examination, particularly if women are not up-to-date with cervical cancer screening or have other symptoms such as pelvic pain, dyspareunia or post coital bleeding. Such examination is also appropriate for patients with persistent bleeding for more than 3 months or a change in bleeding pattern after 3 months of POP use (NICE, 2016).

If these investigations do not suggest an underlying cause, examination is normal, and the woman is otherwise asymptomatic, it can be assumed that the unscheduled bleeding is caused by the POP (NICE, 2016). The bleeding may sometimes settle with time, although there is no evidence to predict those women who will become amenorrhoeic, or those who will continue with persistent irregular bleeding. If patients find the bleeding unacceptable, consider changing to a different type of POP or contraceptive method (NICE, 2016). Although there is no evidence that changing the type or dose of POP will improve bleeding patterns, it may help some women (FSRH, 2015). There is no long-term evidence to support regimes to reduce bleeding with oestrogen supplementation or tranexamic acid (FSRH, 2015).

STI screening

Women should be offered an STI check when they attend for contraceptive checks and informed that only barrier methods such as condoms prevent transmission of STIs. Consider the need for a repeat STI screen according to local protocols or the British Association for Sexual Health and HIV guidelines.

KEY POINTS

The POP is a reliable form of contraception and particularly suitable for women with contraindications to the combined pill such as migraine with aura, VTE or for smokers over age 35 years

The POP is effective within 48 hours when quick-started

The POP works mainly by thickening cervical mucus; the desogestrel POP also suppresses ovulation

Adherence advice and checks are important; missed pill windows are shorter than for the COP, 12 hours for desogestrel POPs and 3 hours for traditional POPs

The bleeding pattern is unpredictable; women should be counselled accordingly at initiation of the POP

If late or missed pills are a problem, make patients aware of the subdermal implant; it uses desogestrel and is 90 times more effective than the POP

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