Contraception – Combined Oral Contraceptive Pill – COCP
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Combined oral contraceptive pills contain both oestrogen and progestogen. This method is:
  • Reliable and reversible
  • Can reduce dysmennorrhoae (painful menstruation) and menoorhagia (heavy bleeding)
  • Can reduce PMT (pre-menstrual tension)
  • Reduce the risk of ovarian, endometrial and colon cancer
  • Reduce the risk of PID
  • An effective treatment for acne and endometriosis
  • Reduce risk of fibroids and ovarian cysts
The COCP pill is frequently prescribed, but, from the prescribers perspective is also one of the more complex methods of contraception due to the long list of contraindications and cautions.
COCP preparations can be divided into three main types:

Monophasic – each pill contains the same amount of progesterone and oestrogen.
Phasic – the concentrations of hormones in each pill varies with the time of the cycle.

  • Both monophasic and phasic pills are in a 21 day supply, with a 7 day break from days to allow breakthrough bleeding. Patients are still protected from pregnancy during the 7 day period, provided all the other pills were taken correctly.

Every Day pills – 28 days supply, with 7 days of placebo pills in days 22-28. The pills must be taken in the right order.

They are available in varying strengths. The lowest dose that produces the desired effects should be used. Typically the oestrogen component is a variant of oestrogen known as ethinylestradiaol – and typically doses are 20 – 40 micrograms. COCPs may contain a variety of progestogens such as norethisterone, levonorgestrel or desogestrel.
  • Note that it is perfectly safe to “run together” courses of the 21 days of active pills. This can be done for up to 12 months at a time if desired
  • Most women have breakthrough bleeding within 120 days of doing this
  • If this occurs, advise patients to stop the pills for 7 days to allow for a withdrawal bleed before recommencing

Prescribing the COCP is not a simple process of “just writing the prescription” although patients may feel frustrated at repeated thorough risk fact-checking at the time of prescription. In my career I have upset many women by refusing to prescribe the pill when contraindicated – even when they have been previously taking it for a long time. I have also seen the death of a teenage girl from massive PE shortly after starting on the pill, and several other cases of PE and huge DVT. This is rare but it certainly comes to mind whenever I write a prescription! – Dr Tom Leach


>99% when taken correctly.
e.g. Microgynon (Ethinylestradiol and levonorgestrel)
Contains both oestrogen and progesterone.
Stops ovulation
Thickens cervical mucus preventing passage of perm, thins lining of uterus preventing implantation.
Very effective when taken correctly
reduces bleeding, pain and PMT.
Reduced hirtuism and acne
Reduces risk endometrial and ovarian ca. Possibly [controversial] inc risk breast ca.
Fertility quick to return when ceased, but can take up to 3 months
Progestrogens cause :Headache, Breast tenderness, breakthrough bleeding
Oestrogens cause: Nausea and vomiting, Fluid retention, Mood changes
Inc risk of cardiovascular disease (thromboembolism)
Absolute CI’s – see UKMEC for a full list
Migraine – with typical focal aura, or severe migraine >72hrs,
Personal history venous or arterial thrombosis,
Heart disease
Previous DVT or PE, Stroke
FHx in first degree relative of VTE
Liver disease
Age >50, or age >35 and smoker
Smoker >40/day any age
Increased BMI – avoid if BMI >35, caution if 30-35
Avoid if two or more of following:
Fx venous thromboembolism / arterial disease, obesity, long-term immobilization, varicose veins.
DM, hypertension, smoking, >35yrs, obesity, migraine
NB: epilepsy (particularly carbamazepine) drugs and ST. john’s Wort interfere with COCP metabolism so patients on these drugs may need higher doses.
Take 21 pills and one week off (some preparations have placebo 7 days, in a 28 day packet)
Start first course on 1st day period. If starting after day 4 of period, or if miss pill >24hr time allocation must use barrier contraception for 7 days.


  • Quoted as >99% effective
  • Described as: if taken correctly, then during the course of 1 year, <1% of women taking the COCP will become pregnant
  • With typical ‘real-world’ use efficacy is more like 91%


  • Prevents ovulation by suppression of LH and FSH
    • LH and FSH levels should not be tested whilst on the pill as the result cannot be interpreted
    • It typically takes about 7 days of hormonal therapy to suppress ovarian function, and 7 days without the pill for it it start functioning again. However, it can take up to 3 months for fertility to return after ceasing the pill
  • Thickens cervical mucous
  • Alters uterine lining to prevent implantation

Side effects

Oestrogen increases the risk of cardiovascular disease (notably thromboembolus). It also causes:

  • Nausea (progesterone does not)

Progestogens can cause: headache, depression, acne, breakthrough bleeding and breast symptoms. Many of these resolve themselves after several weeks/months of treatment, and can be solved if a different progestrogen is used, however, some progestogens are also associated with increased thromboembolic risk

  • Thromboembolic risk – is increased in those taking the COCP, particularly during the first year of use, but the risk is small, and smaller than in pregnancy (when the risk is 60 per 100 000).
  • In all patients the risk of thromboembolism increases with age.
  • There is also an increased risk of DVT when travelling (>5 hour flights) and women should be informed of and encouraged to perform inflight exercises.
  • Breakthrough bleeding is particularly common in the first few months, but usually resolves.
  • The risk of weight gain on the COC is unproven

Missed doses

The general rule is that the combined pill can be taken within 24 hours of the usual time of administration, and still be effective.
If a pill is missed, the woman should take it as soon as she remembers, and then continue taking the rest of the pills at their normal time; even if this means taking two at once
A ‘missed pill’ is one that is >24 hours after she should have taken it

  • Just missing one pill is not a problem, nor is starting a new pack one day late, as long as the missed pill is taken with the next one.

The greatest risk of pregnancy if a pill is missed is at the beginning and end of a cycle.
If 2 pills are missed (i.e. >24 after time should have been taken) then there is a risk of pregnancy – especially if the pill was missed in the first 7 days of the cycle.

  • If the patient has had sexual contact during the missed period, emergency contraception is recommended.
  • If not, then the advice is to continue taking the rest of the pills as normal, and use an additional method of contraception (e.g. condoms) for 7 days. If this 7 days includes the 7 days ‘break’ at the end of the cycle, the next packet should be started immediately, and the ‘break’ omitted.
  • The patient should not take the missed pills if >2 pills were missed.

Vomiting and diarrhoea

  • If vomiting occurs within 2 hours of taking a pill, another pill should be taken
  • If there is vomiting or diarrhoea for >24 hours, then this should be treated the same as a missed pill – i.e: the pills should be taken as normal, but additional contraception (e.g. condoms) should be used for 7 days after the end of the period of illness. If this 7 days runs into the last 7 days of the cycle, the next packet of pills should be started straight away, and the ‘break’ omitted.

Drug interactions

Several drugs are known to reduce the effectiveness of the pill (’enzyme inducing drugs’). You should always check other medications the patient is on (in the BNF) before prescribing a contraceptive, and seek expert advice. Some common examples of interactions are given below:
  • Carbamazepine
  • Pheytoin
  • Phenobarbital
  • St John’s Wort
  • Rifabutin
  • Rifampicin
In women taking these drugs it is advisable to seek alternative methods of contraception

When taking a course of antibiotics

  • Somewhat controversial
  • Previous guidance advised this could affect pill efficacy
  • More recent evidence suggests that it probably doesn’t
  • Many s places still advise additional form of contraception:
    • e.g. use condoms during the course and for 7 days afterwards.
    • If you pass day 21 of the packet, then start a new packet immediately, even for everyday pills.
    • If the course of AB’s lasts longer than 2 weeks, alternative methods of contraception should be sought


It is advisable to discontinue all oestrogen-containing contraceptive 4 weeks before major surgery to reduce the thromboembolus risk. You can safely resume them at the first menses > 2 weeks after surgery.

Contraindications / reasons to stop taking immediately

  • BP >160/95
  • Hepatitis, jaundice, hepatomegaly
  • Prolonged immobility (e.g. usually after surgery)
  • Sudden onset pain:
    • In chest (with/without radiation)
    • Headache
    • Stomach
  • Sudden onset calf swelling
  • Sudden breathlessness
  • Migraine with aura, or migraine lasting >72 hours, or migraine resistant to treatment
    • Increased risk of ischaemic stroke in these patients
  • Age over 50
  • Smoker >40/day
  • Diabetes with complications, or diabetes >20y
  • Breast feeding – avoid during the first 6 months due to effects on lactation
  • BMI >35, caution if BMI 30-35


If two or more of the following are present, alternative contraception should be recommended
  • Age over 35
  • Obesity
    • BMI >30-35
  • Migraine (without aura)
  • BP >140/90
  • Smoker <40/day
  • FHx of arterial disease
  • Diabetes <20y


Women with RF’s for cardiovascular disease should be prescribed the lowest does of oestrogen (20micrograms ethinylestradiol), or should be prescribed an alternative if >2 RF’s are present
Women >50 should not use the COC as better alternatives are available, and the cardiovascular disease risk is high
Inform patient to seek help immediately if:

  • Migraines, sudden onset chest pain/breathlessness/haemoptysis, swollen calves, weakness is limbs / other signs of TIA/stroke

Missing the withdrawal bleed

  • It is ok to use two packets one after the other (i.e. start the second packet on day 22). This can be done for up to 3 months in a row. Tell the patient the lining of the womb does not keep on growing during this time!
  • Remember to tell patients on the everyday pill to start the new packed on day 22

Length of prescription

  • Normally when first prescribed, given for 3 months. After this time, BP will be checked, and if no problems or additional RF’s, then will be prescribed for 1 year at a time.

Commencing treatment

No Previous contraception

  • Start on day 1 of cycle, OR
  • If starting after day 4 of cycle, use extra method (e.g. condom) for first 7 days

Changing from progesterone only pill

  • Start on first day of cycle, OR
  • If amenorrhoea, exclude pregnancy then start on any day

After child birth

  • If not breastfeeding, start 3 weeks after birth (otherwise, ↑risk of thrombosis)
  • If started after 3 weeks, other methods of contraception (e.g. condoms) required for first 7 days.
  • DO NOT USE IN BREASTFEEDING – alters lactation

After miscarriage / abortion

  • If less than 24 weeks, start pills straight away. If >24 weeks, seek advice


  • Microgynon
  • Qlaira

Alternative preparations

Skin patch

  • May have a higher risk of thromboembolism than the oral preparation
  • Treatment consists of three patches. First patch applied on day 1 of cycle, second on day 8, and third on day 15. Remove old patch each time, and remove third patch on day 22, and have a week with no patch.
  • If the first patch is applied on any day other that day 1, another method of contraception (e.g. condoms) need to be used for 7 days
  • Withdrawal bleeding occurs during patch-free week


Vaginal contraceptive ring

  • A small rubber ring that can be inserted into the vagina by the patient, and then sits around the cervix. Stays in place for 3 weeks. Remove after 3 weeks, and have 1 week without ring present (similar to pill and patch)
  • Withdrawal bleeding occurs during ring-free week

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Dr Tom Leach

Dr Tom Leach MBChB DCH EMCert(ACEM) FRACGP currently works as a GP and an Emergency Department CMO in Australia. He is also a Clinical Associate Lecturer at the Australian National University, and is studying for a Masters of Sports Medicine at the University of Queensland. After graduating from his medical degree at the University of Manchester in 2011, Tom completed his Foundation Training at Bolton Royal Hospital, before moving to Australia in 2013. He started almostadoctor whilst a third year medical student in 2009. Read full bio

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