Postinor

Also called the emergency contraceptive pill or the “morning after pill”

Postinor is an emergency contraceptive pill (ECP) to prevent pregnancy. Find out how to take it safely and possible side effects. Postinor is also called levonorgestrel.

What is Postinor ?

Postinor is an emergency contraceptive pill (ECP) used to prevent pregnancy, for example if you have unprotected sex, if your regular method of contraception fails (eg, a burst condom) or you forgot to take your regular contraceptive pill.

Postinor is a high dose of the progestogen hormone called levonorgestrel. You have to take 1 or 2 pills within 72 hours of having sex. Postinor has about 98% success rate for those of average weight. It may not work for heavier people.

You can buy Postinor from a pharmacist or get it from the family planning clinics or your healthcare provider on prescription. Read more about where to get Postinor below.

How do I take Postinor?

Postinor is approved to be taken up to 72 hours after sex (within 3 days). However, for most people it is still effective up to 4 days after sex.

  • If you weigh up to 70kg, take 1 pill within 72 hours of unprotected sex.
  • If you weigh over 70kg, Postinor is not the preferred choice to prevent pregnancy. A copper IUD is most effective. If you want to take Postinor, 2 pills together may be more effective, although there is no proof of this yet.

You may feel sick after taking Postinor so it helps to take it with food. If you vomit within 3 hours of taking your dose you will have to get another.

  • Postinor can be taken at any time in your menstrual cycle. 
  • Swallow the tablet whole with water – do not chew.
  • Don't delay taking the tablet, make sure you take the tablet within 72 hours. The tablet works best the sooner you take it after having unprotected sex.
  • If you are already using a regular method of contraception such as the contraceptive pill, you can continue to take this at your regular times.

Who should not take Postinor?

The use of the Postinor is not advised if you have:

  • a condition that affects your small bowel (such as Crohn’s disease) because the medicine might not be absorbed 
  • severe liver problems
  • a history of ectopic pregnancy (where the baby develops somewhere outside the womb)
  • had a disease called salpingitis (inflammation of the fallopian tubes).

A previous ectopic pregnancy or previous inflammation of the fallopian tubes increase the risk of a new ectopic pregnancy.

How does Postinor work?

Postinor works in a few ways to prevent pregnancy by:

  • Stopping or delaying the release of an egg from your ovaries. 
  • Preventing the sperm from fertilising an egg by changing the way the sperm moves in your body.
  • Delaying ovulation, but there is a risk of pregnancy if you have unprotected sex later in your cycle. It doesn’t work once the egg has been released and fertilised. 

There is no evidence that Postinor will affect the unborn baby if you do become pregnant. It doesn’t harm you or the developing embryo. 

How effective is Postinor?

It has a success rate of 98% for those of average weight when taken within 4 days of unprotected sex.

If you weigh more than 70kg

Postinor may not work so well if you weigh more than 70kg, or have a body mass index (BMI) over 26 kg/m2. In this situation, a copper IUD is recommended. If you decide you want to take Postinor, you may be advised to take a double dose – 2 pills together.

If you are taking other medicines

Tell your healthcare provider about any other medicines you are taking including prescribed, over-the-counter, from a supermarket or health food shop.  

Some medicines may prevent Postinor from working well. Postinor may be less suitable for you if you have used any of the following medicines during the last 4 weeks:

  • Medicines to treat epilepsy such as phenytoin, carbamazepine, phenobarbitone.
  • Medicines used to treat tuberculosis such as rifampicin, rifabutin.
  • Treatment for HIV (eg, ritonavir or efavirenz) or Paxlovid for COVID-19
  • A medicine used to treat fungal infections (griseofulvin).
  • Herbal remedies containing St John’s Wort (Hypericum perforatum).

In these situations, a copper IUD is recommended. If you decide you want to take Postinor, talk to your healthcare provider. They may recommend to take a double dose – 2 pills together.

What can I expect after taking Postinor?

  • Some women may notice bleeding or spotting and you may have an early or later start to your next menstrual period.
  • Even if you have a period, it's important to have a pregnancy test 3–4 weeks after taking Postinor to make sure you are not pregnant.

Where can I get Postinor?

  • Most community pharmacies
  • Your GP clinic (or find a GP)
  • Accident and emergency clinics
  • Sexual health clinics
  • Family planning clinics.

To make sure Positinor is right for you, your healthcare provider will usually ask you questions about:

  • your usual means of contraception
  • why you need emergency contraception
  • the number of hours since you last had unprotected sex
  • your period
  • whether you have had a pregnancy test recently
  • existing medical conditions such as unexplained vaginal bleeding or Crohn’s disease
  • other medicines you are taking, including those prescribed or bought over-the-counter, or from a supermarket or health food shop
  • health symptoms such as burning or pain when passing urine, lower abdominal pain, pain during or after sex, unusual vaginal discharge and irregular vaginal bleeding or spotting.

This information helps your healthcare provider decide if this type of emergency contraception is safe and suitable for you.

Possible side effects of Postinor

Like all medicines, Postinor can cause side effects, although not everybody gets them.

Very common (may affect more than 1 in 10 people)

  • feeling sick (nausea)
  • some irregular bleeding until your next period
  • lower abdominal pain
  • tiredness
  • headache.

Common (may affect up to 1 in 10 people)

  • Being sick (vomiting). If you vomit within 3 hours of taking Postinor you will have to get another.
  • Your period might be different. Most people will have a normal period at the expected time, but some may have their period later or earlier than normal. You might also have some irregular bleeding or spotting until your next period. If your period is more than 5 days late or is unusually light or unusually heavy, you should contact your doctor as soon as possible.
  • You might have tender breasts, diarrhoea or feel dizzy after taking this medicine.

Very rare (may affect up to 1 in 10,000 people)

  • Rash, hives, itching, swelling of the face, pelvic pain, painful period.

Tell your doctor or pharmacist if you notice anything that is making you feel unwell.

Learn more

Emergency contraceptive pill Family Planning NZ
Emergency contraception Family Planning NZ

References

  1. Levonorgestrel (contraception, emergency) New Zealand Formulary
Credits: Health Navigator Editorial Team. Reviewed By: Angela Lambie, Pharmacist, Auckland Last reviewed: 20 Oct 2022