Key practice points:
- Combined and progestogen-only oral contraceptives are equally effective for preventing pregnancy; the estimated rate
of pregnancy is 2–3 per 1000 during the first year if used correctly and consistently, however, with typical
use, the rate of pregnancy is 90 per 1000
- A reasonable choice for a first-time combined oral contraceptive (COC)-user is a formulation containing ≤ 30 micrograms
ethinylestradiol with either levonogestrel or norethisterone
- Avoid use of COCs in patients with risk factors for venous thromboembolism, myocardial infarction or ischaemic stroke,
such as those aged over 35 years who smoke, have migraine with aura or are likely to be immobile for a prolonged
period, e.g. undergoing major surgery
- Progestogen-only oral contraceptives, commonly referred to as progestogen-only pills (POPs), can be used if oestrogen
- COCs can be initiated from six weeks post-partum in patients who are breastfeeding; previous guidance recommended
waiting until six months post-partum
Oral contraceptives are available in two formulations, a combined ethinylestradiol/ progestogen pill and a progestogen-only
pill (POP). Combined oral contraceptives (COCs) are generally the first-line choice for those who wish to use an oral
contraceptive, unless oestrogen use is contraindicated. This is because COCs require less strict adherence to regular
dosing times than POPs and provide additional non-contraceptive benefits. When COCs and POPs are taken correctly, the
estimated rate of pregnancy is 2–3 per 1000 during the first year of use.1
COCs prevent ovulation, thicken cervical mucus to inhibit sperm penetration of the upper reproductive tract and alter
the endometrial lining to make implantation less likely. They are taken as one pill, daily, at approximately the same
time of day.
All COCs in New Zealand contain the same oestrogen (ethinylestradiol) in varying doses along with differing progestogens
(Table 1). The progestogens vary in their androgenic properties; noresthisterone and levonorgestrel are more androgenic
than desogestrel; drospirenone and cyproterone are anti-androgenic and therefore most effective for treating acne.2
Which COCs are available in New Zealand?
A range of fully or partly subsidised* COCs are available in New Zealand. Other unsubsidised oral formulations
are also available. Formulations with lower doses of ethinylestradiol are just as effective for preventing pregnancy as
those with a higher dose.3, 4
* For partly subsidised COCs, higher subsidy is available with Special Authority approval for
patients with a low income if at least one fully subsidised option has been trialled and not tolerated, see:
Table 1: COC formulations available in New Zealand 5
ED = every day formulation – this is a COC regimen that includes placebo pills to be taken during the hormone-free interval.
NB. Not all brand names include “ED” even though they are an ED regimen.
† COC formulations that do not contain placebo pills
* Brevinor will be delisted from 01 July, 2019 and Brevinor-1 21 Day will be delisted from 1 Jan, 2020
Venous thromboembolism (VTE) risk
COC use is associated with a three to 3.5-fold increase in the relative risk of VTE.1 However, if there are
no additional risk factors, the absolute risk of VTE associated with COC use is very small, particularly when compared
to the risk during pregnancy and post-partum (Table 2).1 The risk of VTE is highest in
the first few months after initiating a COC and reduces over the first year of use.1
If the patient has existing risk factors for VTE, the absolute risk is higher and COCs should not be used.
For information on non-oestrogen-containing contraceptive options appropriate for patients at high risk
of VTE, see: “Contraception: which option for which patient”.
Risk factors for VTE that are contraindications to COC use include:1, 5, 6
- Current or past VTE
- Thrombogenic mutations, e.g. factor V Leiden,* prothrombin mutation, Protein S, Protein C, antithrombin
- Major elective surgery, any surgery to the legs or surgery resulting in prolonged immobility, i.e. more than one week†
- Age ≥ 35 years and smoke ≥ 15 cigarettes per day‡
* If homozygous for factor V Leiden or heterozygous with a history of VTE, COCs should be avoided.
If heterozygous but no history of VTE and no alternative contraceptive is suitable, COCs may be used but avoid formulations
with a higher VTE risk (Table 5).7
† The COC should be stopped four weeks prior to surgery and can be restarted from two weeks after mobilisation.8 These
recommendations do not apply to minor surgical procedures, e.g. a tooth extraction, or those requiring a short duration
of general anaesthesia (< 30 minutes).8
‡ Increasing age and smoking are independent risk factors for VTE, however, when these factors are in combination,
the additive risks are considered to outweigh the benefits of COCs.1
Risk factors for VTE where COC use is strongly cautioned, include:1
- Family history of VTE in a first-degree relative aged < 45 years
- Immobile for a prolonged period due to illness or disability, i.e. without the added risk of VTE associated with surgery
- Aged ≥ 35 years and smoke < 15 cigarettes per day or stopped smoking less than one year ago
- Obesity (body mass index [BMI] ≥ 35 kg/m2)
Table 2: Risk of VTE for different patient groups9, 10
||Risk of VTE per 10,000 females per year
|Childbearing age, non-COC users
|Pregnant and post-partum
* The risk of VTE two days before and after delivery is estimated to be 300–400 per 10,000 females
per year and for the first 12 weeks post-partum is 40–65 per 10,000 females per year
Best practice tip: Remind patients who use COCs and are going to be travelling to maintain
mobility on long-haul flights (> 3 hours). Compression stockings are not essential unless other risk factors for VTE
are present.1 If the patient is going to spend more than one week at an altitude > 4500 metres they should
consider switching to a non-oestrogen-containing contraceptive, particularly if they have other risk factors for VTE.1
Other cardiovascular disease (CVD) risk
COC use is associated with a 1.6-fold and 1.7-fold increase in the relative risk of myocardial infarction and ischaemic
stroke, respectively.11* However, the absolute risk of each of these outcomes is small unless additional
risk factors for arterial disease are present.1 It is estimated that among 10,000 females the use of COCs
for one year would result in:1
- Two additional cases of thrombotic stroke
- One additional case of myocardial infarction
* The duration of COC use was not reported in this meta-analysis
COCs should not be used if there are additional risk factors for myocardial infarction or stroke, including:1
- Hypertension (systolic ≥ 140 mmHg or diastolic ≥ 90 mmHg) or use of antihypertensive medicines, even if hypertension
is well controlled
- Multiple risk factors for CVD, e.g. increasing age, smoking, hypertension, obesity, dyslipidaemia, diabetes
- Current or past ischaemic heart disease, stroke, complicated valvular or congenital heart disease, e.g. pulmonary
hypertension, and other vascular disease
- Impaired cardiac function or atrial fibrillation
- Migraine with aura or migraine without aura that is new onset during use of COC *
* Could consider initiating a COC with caution if history of migraine without aura, provided
no other CVD risk factors
Current breast cancer
COCs should not be used in patients with current breast cancer and use is strongly cautioned against in those with a
history of breast cancer or who are known carriers of gene mutations associated with breast cancer, e.g. BRCA1 or BRCA2.1
N.B. COCs may be protective against ovarian cancer associated with these mutations; discussion with an
oncologist is recommended.
COCs can be started from six weeks post-partum if breastfeeding, provided breastfeeding is well established and there
are no concerns with the infant’s growth.1, 12
COCs can be started from three weeks post-partum if not breastfeeding, provided there are no other risk factors for
VTE;* those with additional risk factors should wait six weeks to begin the COC.1
* Other risk factors for VTE post-partum include immobility, transfusion at delivery, BMI ≥ 30
kg/m2, caesarean section delivery, haemorrhage, pre-eclampsia, smoking
For further information on suitable contraceptive options post-partum, see: ”Contraception:
which option for which patient?”.
Age ≥ 50 years
The use of COCs is not recommended in those aged ≥ 50 years due to the risks outweighing the benefits.13
For further information on suitable contraceptive methods for older patients, see: ”Contraception:
which option for which patient”.
For further information on medical conditions where COC use is contraindicated or cautioned, e.g. systemic lupus erythematosus, refer to the
New Zealand Formulary: www.nzf.org.nz/nzf_4178 and the United
Kingdom Medical Eligibility Criteria:
A reasonable option for a first-time COC user is 30 micrograms ethinylestradiol with either 150 micrograms levonorgestrel
or 500 micrograms norethisterone. A lower dose of ethinylestradiol is recommended for older patients, e.g. > 40 years.13
The choice of oral contraceptive may also be influenced by whether the patient seeks non-contraceptive benefits from
the medicine, e.g. a formulation containing cyproterone may be appropriate for a patient with acne or polycystic ovary
syndrome, however the benefits should be weighed against the higher VTE risk.
If a patient experiences adverse effects with one COC, another formulation may be trialled (see: “Adverse
effects depend on dosing and formulation” and Table 3).
COCs can be initiated on any day of the menstrual cycle, however, if starting six or more days after the onset of menses,
condoms should be used for the first seven days of hormone pills.
Table 3: Managing adverse effects associated with COCs1, 2, 4, 5
||Increase oestrogen; and/or
Decrease progestogen or select a less androgenic or anti-androgenic progestogen, i.e.
desogestrel, drospirenone* or cyproterone
||Decrease oestrogen; and/or
Change to a progestogen with a mild diuretic effect, i.e. drospirenone*
||Increase oestrogen; and/or
Change the type of progestogen, e.g. levonorgestrel or desogestrel
||Decrease oestrogen and/or progestogen; and/or
Change progestogen, e.g. levonorgestel
||Decrease oestrogen; and/or
Change progestogen, e.g. levonorgestrel
If headaches occur in the hormone-free interval, consider an extended or continuous regimen
|Abdominal cramping or heavy bleeding during the hormone-free interval
||Extended or continuous regimen
||Decrease oestrogen and/or take the pill at night
Change to a POP
* Drospirenone may increase potassium levels. If there are risk factors for hyperkalaemia such as renal insufficiency,
liver dysfunction or adrenal gland insufficiency a COC containing this progestogen should not be used. COC formulations containing
drospirenone are currently not subsidised in New Zealand.
Tailored regimens can be offered to omit the pill-free week
COCs are typically taken in a regimen of 21 “active” hormone pills followed by a hormone-free interval of seven days,
during which withdrawal bleeding occurs. However, there is no evidence to support any health benefits from having a monthly
withdrawal bleed.1 Lengthening the hormone-free interval by missing pills at the beginning or end of a cycle
may increase the risk of pregnancy by allowing follicular development and ovulation in some patients.1
Omitting the hormone-free interval may improve contraceptive effectiveness, reduce heavy bleeding and improve symptoms
associated with the withdrawal bleed, such as bloating/fluid retention, headache and altered mood.1, 6 Data
directly comparing the risk of cardiovascular events and cancer between standard and extended regimens are not yet available,
however indirect evidence suggests no difference in cardiovascular risk.1 There is also no evidence of endometrial
thickening or histological abnormalities with extended or continuous regimens.1 There is an increased risk
of breakthrough bleeding when pills are taken continuously, but this declines with time.14
If breakthrough bleeding persists for three to four days when taking pills continuously, the pills should
be stopped for four days and then resumed.1
If patients do not wish to omit the hormone-free interval completely, another option is to shorten this period from
seven to four days. This reduces the chance of return to ovarian activity and therefore may decrease the risk of contraceptive
failure, e.g. if pills are missed.1
A tailored regimen can be recommended to patients who are starting or already using a COC (Table 4).
There is an additional cost associated with requiring more pill packs per year, i.e. if used continuously, a six-month
prescription will last 18 weeks instead of 24 weeks. However, this cost may be offset by savings made from not having to
purchase sanitary products.
Table 4: Examples of different regimens for COC use1
||Duration of hormone pills (days)
||Hormone-free interval (days)
|Shortened hormone-free interval
||63 or 84, i.e. 3 or 4 packets of pills
||4–7 (every 3–4 packets of pills)
||Continuous use of active pills
Ensure that patients understand how to follow the tailored regimen correctly
Tailoring a COC regimen requires deviation from the instructions on the COC packaging which may lead to medicine errors.
Discuss the regimen options with the patient and ensure that they understand how to omit the hormone-free interval, i.e.
by discarding the unused placebo pills and starting on the next pack of active pills.
For further information on initiating an oral contraceptive, including changing from another method of contraception,
refer to the New Zealand Formulary: www.nzf.org.nz/nzf_4163
Patient information on how to take a pill continuously can be found here:
Adverse effects and risks associated with COC use depend on dosing and formulation
Lower doses of oestrogen are associated with lower risks. Research has shown that doses of 20 micrograms
of ethinylestradiol, daily, are associated with lower risks of VTE, stroke, and myocardial infarction than doses of 30
micrograms and above, daily, but more risk of breakthrough bleeding.1
The choice of progestogen may influence risks: Evidence regarding the safety of different progestogens
is conflicting but suggests that COCs containing levonorgestrel or norethisterone may be associated with lower rates of
VTE (Table 5), stroke, and myocardial infarction than COCs containing the newer generation progestogens.1 In
addition, discontinuation rates due to adverse effects such as headache, breast tenderness and nausea are lower for levonorgestrel-containing
than norethisterone-containing COCs.16
Table 5: VTE risk according to COC formulation9, 10
||Risk of VTE per 10,000 females per year
|Low-dose* COC with levonorgestrel or norethisterone
|Low-dose* COC with drospirenone, desogestrel, cyproterone
|High-dose† COC with levonorgestrel
* Low dose = 20–35 micrograms ethinylestradiol
† High dose = 50 micrograms ethinylestradiol
COCs are associated with a reduced risk of several cancers including endometrial, ovarian and colorectal cancers, but
an increased risk of breast and cervical cancers.1
A longitudinal study conducted in the United Kingdom which followed females* for up to 44 years estimated
that COC use resulted in the prevention of:17
- 19% of colorectal cancers
- 34% of endometrial cancers
- 34% of ovarian cancers
COC use was associated with an estimated:
- 25% of cervical cancers†
- 3% of breast cancers
The increased risk of breast and cervical cancer was only present in current and recent users; the risk was no longer
present in this study five years after stopping the COC.17
* Average age at recruitment was approximately 28 years; 82% had at least one child at the
time of recruitment
† Human papillomavirus (HPV) infection is necessary for the development of cervical cancer.
It is not certain whether the COC itself increases the risk of cervical cancer, or whether its use
is associated with an increase in HPV infection rates due to sexual activity without a condom. COC
use for more than five years is associated with a small increase in the risk of cervical cancer,
but the risk reduces over time.1
Evidence of an association between COC use and changes in mood is variable. In one study of over 600 females, 16% reported
a deterioration in mood while 12% reported an improvement in mood with use of COCs.18 COCs should be used with
caution if there is a history of depression and all patients should be monitored for abnormal changes in mood.5
Weight gain due to use of COCs is unlikely
A 2014 Cochrane review covering 49 studies concluded there was no convincing evidence that use of COCs affects body
weight or composition, and if any effect exists it is likely to be small.19
Managing breakthrough bleeding associated with COC use
Some patients may experience breakthrough spotting or bleeding while taking COCs. This is more common within the first
three months of initiation and typically settles over time.1
When prescribing a COC, inform patients about the possibility of breakthrough bleeding and provide reassurance that
this does not reduce the contraceptive effectiveness of the COC. Patients should also be reminded that missing a pill
increases the risk of breakthrough bleeding and, depending on when in the pack it is missed, may reduce the contraceptive
If bleeding does not settle after three months and other causes have been excluded, consider the following strategies
to improve breakthrough bleeding:1 ,2
Increasing oestrogen dose: changing to a formulation with a higher dose of ethinylestradiol (to a maximum
of 35 micrograms)
Changing progestogen type: limited evidence suggests that a levonorgestrel-containing COCs may be preferable
over a formulation containing norethisterone, and that desogestrel may be preferable to levonorgestrel
Smoking cessation: breakthrough bleeding is more common in COC users who smoke although the mechanism for
this is not well defined
If the first instance of breakthrough bleeding is more than three months following the initiation of the COC or bleeding
is persistent consider whether there might be another clinical explanation, e.g. missed pills, sexually transmitted infection,
pregnancy, cervical pathology.
Progestogen-only formulations are a suitable alternative for those who wish to use an oral contraceptive but have contraindications
to oestrogen use or prefer not to use a COC.
POPs thicken cervical mucus to inhibit sperm penetration and may also prevent ovulation (50% of cycles).20 The
desogestrel-only formulation consistently inhibits ovulation (97% of cycles), but is not subsidised in New Zealand (Table
POPs can be initiated on any day of the menstrual cycle, however, if starting six or more days after the onset of menses,
condoms should be used for the first two days (48 hours) of hormone pills.
Which POPs are available in New Zealand?
There is currently one fully subsidised POP available in New Zealand (Table 6). Although robust
head-to-head studies are not available, evidence suggests that when used correctly the different formulations of POPs
available in New Zealand are equally effective in preventing pregnancy.20
Table 6: POP formulations available in New Zealand 5
|Progestogen type and dose
|Desogestrel 75 micrograms
|Levonorgestrel 30 micrograms
|Norethisterone 350 micrograms
Cautions and contraindications to POP use
POPs should not be used in patients with current breast cancer. They may be considered with caution, i.e. only if there
are no other suitable options, if cancer has been in remission for more than five years.21 POPs, as with COCs,
should be used with caution in patients with systemic lupus erythematosus who are positive for antiphospholipid antibodies,
and in those with some liver diseases, e.g. decompensated cirrhosis.21
Correct and consistent use is essential for POPs to provide effective contraception
POPs are taken continuously, i.e. an active pill each day. Advise patients considering a POP that regular adherence
is essential for these medicines to be maximally effective. Norethisterone and levonorgestrel-only pills must be taken
within three hours of the regular dosing time each day. Desogestrel-only pills have a wider window for error and must
be taken within 12 hours of the regular dosing time.
POPs offer the same level of contraceptive effectiveness as COCs and can be used in clinical situations where COCs are not recommended.20
POPs may be used when breastfeeding and can be initiated at any time post-partum, unlike COCs which should not be used in the first six
weeks if breastfeeding (see: “Cautions and contraindications: when to avoid COCs”).1
Bleeding patterns may be unpredictable, due to the variable inhibition of ovulation; it is estimated that
50% of patients using a POP will continue to have a normal menstrual cycle, 40% an irregular menstrual cycle and 10% no
menstrual cycle.22 Up to 70% of patients using POPs report breakthrough bleeding and 10% report frequent
bleeding, i.e. more than five episodes in 90 days.20, 23
Problematic bleeding does not always settle over time. Changing to a different POP, e.g. a desogestrel-only pill, may
improve bleeding regularity in some patients.20 An alternative method of contraception may be required in
N.B. There is no convincing evidence that POPs cause weight gain.24
The effectiveness of COCs and POPs can be reduced by interactions with medicines that induce hepatic metabolism by the
CYP3A4 enzyme, e.g. rifampicin, rifabutin, carbamazepine, oxcarbazepine, nevirapine, phenytoin, phenobarbital, primidone,
ritonavir, St John’s wort and topiramate.25 COC or POP absorption may be reduced by concurrent use of laxatives
if they cause diarrhoea or are used excessively or inappropriately.
Interactions between oral contraceptives and other medicines can be checked here: www.nzf.org.nz/nzf_1
Managing patients taking enzyme-inducing medicines 25
Patients who are taking an oral contraceptive and an enzyme-inducing medicine short-term, i.e. less than two months,
should be advised to use condoms for the duration of treatment with the enzyme-inducing medicine and for a further four
weeks after stopping.*
* Using a high-dose COC, e.g. 50 micrograms of ethinylestradiol, has been suggested to counteract
the change in hepatic metabolism, however there is no data on the contraceptive effectiveness of this approach.26
If the enzyme-inducing medicine is required long-term, recommend an alternative contraceptive, e.g. medroxyprogesterone
injection or an intrauterine device.
For further information on the use of antiepileptic medicines in females, see:
Most broad-spectrum antibiotics do not interact with oral contraceptives
Most antibiotics, aside from rifampicin and rifabutin, do not have a clinically relevant interaction with oral contraceptives
and patients do not need to take extra precautions as long as they are taking their contraceptive consistently and correctly.1 However,
if the antibiotic or the illness it is treating causes vomiting or diarrhoea, additional contraceptive precautions might
be required (see: “Recommendations for missed COCs or POPs”).
Recommendations for missed COCs or POPs1, 5
A missed COC pill is when ≥ 24 hours have passed since the regular dosing time. The missed pill should
be taken as soon as it is remembered, and the next pill taken at the usual time, even if that means taking two pills at
once. No extra contraceptive precautions are necessary.
If two or more COC pills are missed, one active pill should be taken as soon as it is remembered, and
the normal regimen then resumed. Condoms should be used, or sex avoided, until seven consecutive hormone pills have been
taken. For patients using a standard COC regimen, additional precautions depend on when in the regimen the pills are missed:
- Week 1 (after hormone-free interval) – if unprotected sex has occurred during the hormone-free interval or week 1,
consider use of emergency contraception
- Week 3 (prior to hormone-free interval) – omit the hormone-free interval
Theoretically, up to eight consecutive pills could be missed during week 2 or 3 of a standard regimen or at any time
during a continuous regimen, before additional contraceptive precautions would be required (provided the hormone-free
interval is omitted if the missed pills are in week 3 of a standard regimen, and seven hormone pills were taken consecutively
before the missed pills). However, evidence is lacking on the outcomes of this practice therefore there is currently a
lack of consensus on this recommendation.
For POPs, a missed pill is if more than three hours have passed since the regular dosing time for norethisterone
or levonorgestrel-only pills or more than 12 hours for desogestrel-only pills. The missed pill should be taken
as soon as it is remembered. If more than one pill has been missed, only one should be taken. The next pill should be
taken at the regular dosing time and condoms should be used, or sex avoided, for the next 48 hours. If unprotected intercourse
has occurred after the missed pill and within 48 hours of restarting the POP, emergency contraception should be used.
Vomiting and diarrhoea may interfere with the absorption of COCs and POPs. If vomiting occurs and less
than two hours have passed since taking a COC or POP, another pill should be taken as soon as possible. If the replacement
POP is taken more than three hours after the regular dosing time (12 hours for a desogestrel-only pill), additional contraceptive
precautions will need to be taken during the illness and until two consecutive hormone pills have been taken.
If vomiting or diarrhoea is persistent, i.e. lasting more than 24 hours, an additional contraceptive method should be
used during the illness and until:
- Seven consecutive hormone pills have been taken if using COCs
- Two consecutive hormone pills have been taken if using POPs
Reminder: accredited pharmacists can supply selected oral contraceptives without a prescription
The reclassification of selected oral contraceptives in 2017 allows accredited pharmacists to supply the following formulations
without a prescription to medically eligible patients:27
- COCs with ≤ 35 micrograms of ethinylestradiol combined with levonorgestrel or norethisterone (can be supplied to patients
aged 16 – 39 years)
- POPs with levonorgestrel, norethisterone or desogrestrel alone (can be supplied to patients aged 16 – 52 years)
Registered pharmacists must complete an approved training programme to be able to supply these oral contraceptives.
A comprehensive assessment is required to determine whether the patient meets the requirements for the pharmacist-supply
of the COC or POP. The selected oral contraceptive must have been prescribed by a medical practitioner in
the last three years, the patient must have had at least one further appointment with a medical practitioner since initiating
the oral contraceptive and the patient must see a medical practitioner at least once every three years (to assess continued
suitability of the oral contraceptive and for a sexual health check). The pharmacist must supply the same formulation
of oral contraceptive that the patient was originally prescribed (refer to the Practice Guidelines for some exceptions
to this). With consent from the patient, the pharmacist should notify the patients medical practitioner that they are
supplying their COC or POP.
The practice guidelines for the pharmacist-supply of selected oral contraceptives is available here:
Thank you to Dr Beth Messenger, National Medical Advisor, Family Planning New Zealand for expert review of this article
N.B. Expert reviewers are not responsible for the final content of the article.
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