Progesterone-only pill

There are two main types of pill which vary in hormone content and the way they work. The most widely used are the combined pills which have two hormones, oestrogen and progestogen. There are also progestogen-only pills which have progestogen only and no oestrogen.

There are two types of progestogen-only pills available in Ireland, Noriday and Cerazette, which differ in the way they work and instructions for what to do if you miss a pill. This Factsheet is about the progestogen-only pill.

How does it work?

The main action of progestogen-only pills is to thicken the mucus in the neck of the womb. This makes it difficult for sperm to reach the egg. The progestogen-only pill sometimes stops your ovaries from releasing an egg (prevents ovulation). This is the main action of one of the newer progestogen-only pills, Cerazette. This is the reason that there are different instructions if you take a pill late for Cerazette as compared with older types of the progestogen-only pill (Noriday is the only other progestogen-only pill available in Ireland).

How effective is it?

As with any contraceptive its effectiveness depends on how well the instructions are followed. With perfect use the progestogen-only pill is over 99% effective meaning that less than 1 woman in 100 will become pregnant in a year.

But with less careful and consistent use, more women will get pregnant.

This pill is even more effective in women over 40 years of age. To make the pill as effective as it can be, remember:

  • To take it regularly, and at the same time each day.
  • Use another contraceptive method as well if you miss a pill or are sick, have severe diarrhoea, or are taking medicines which may interfere with the pill.

Where do you get the progestogen only pill?

You can only get the pill from a doctor. Family Planning Clinics and most doctors will prescribe it.

You will have to pay a consultation fee and prescription cost. It is available on the GMS (Medical Card Scheme). The doctor will take a detailed medical and family history to make sure the pill is suitable for you. You should also have your blood pressure checked.

What are the advantages?

  • It is a very effective method when used correctly
  • It is easy to use and does not interrupt sex
  • There are no serious side-effects
  • May help with pre-menstrual tension and painful periods
  • You can use it if you are breastfeeding
  • You can use it at any age
  • You can use it if you are over 35 and you smoke (not advised with combined pill)
  • May be an alternative for women who cannot take the combined pill

What are the disadvantages?

  • You need to remember to take the pill daily and at the same time every day or it will not work.
  • The pill does not protect you against sexually transmitted infections.
  • Your period may change in a way unacceptable to you. Some women find their periods stop completely or become irregular, light or more frequent. This may settle down and is not harmful but you may find it annoying. Speak to your doctor as changing to a different brand might help.

Who is it suitable for?

Not everyone can use the progestogen-only pill so your doctor or nurse will need to ask you about your own and your family’s medical history to make sure the pill is suitable. Do mention any illnesses or operations you have had.

The following are some of the conditions which may mean the progestogen-only pill is not suitable for you:

  • You think you might already be pregnant
  • You take certain medications (only a small number of medications interfere with the progestogen-only pill)
  • You have liver disease or have recently recovered from liver disease
  • You have had heart disease or stroke
  • You have breast cancer or have had breast cancer in the past
  • You have systemic lupus erythematosus (SLE or Lupus)
  • You have irregular vaginal bleeding

However, if you are healthy and have no medical conditions which make it unsuitable for you, you can take the progestogen-only pill until menopause or age 55.

How is it taken?

You may start the progestogen-only pill at any time. Use another method of contraception if you have vaginal intercourse during the first 48 hours of pill use — protection will begin after two days.

Taking the progestogen-only pill at the same time each day is important. Be sure to follow the instructions on your pill package.

What if you forget a pill?

Take it as soon as you remember, and take the next one at the right time. This may mean taking two pills in one day. This is not harmful.

If you take the Noriday pill more than 3 hours late, you are not protected. Continue to take your pills as soon as possible and you will be protected after 2 days of taking your pill normally. Until then, either use condoms or abstain from sex.

If you are taking Cerazette, you will be unsafe (not protected against pregnancy) if you are more than 12 hours late in taking your pill. Again, your protection against pregnancy will return after 2 days of taking the pill normally.

If you vomit within two hours of taking the pill or if you have very severe diarrhea the pill may not be effective and you should use an extra method of contraception such as a condom during the stomach upset and for two days after.

Are there any side-effects?

When starting the pill some women may experience: breast tenderness, spotty skin, headaches, a bloated feeling, or have some breakthrough bleeding (bleeding between periods).

Although these can be a nuisance, they are not dangerous and should disappear within the first few months using this contraceptive.

Cysts on the ovary may occur in progestogen-only pill users, but are not dangerous. These may cause pain, but often there are no symptoms. These cysts usually disappear without treatment when you stop taking the pill.

Research about the risk of breast cancer, cervical cancer and hormonal contraception is complex and contradictory. Current research suggests that users of all hormonal contraception appear to have a small increase in risk of being diagnosed with breast cancer compared to non-users of hormonal contraception. Further research is ongoing. All risks and benefits should be discussed with your doctor.

What about other medications I am taking?

However, some other medicines may interfere with the way the pill works. These include some drugs that treat epilepsy, HIV and TB, as well as the ‘natural’ remedy St. John’s wort. You may have to use another method as well, such as the condom, while you are taking the medicines, and up to a further four weeks afterwards. If you are taking these medicines on a long term basis, oral contraceptives are probably not the best method for you. Always mention you are on the progestogen-only pill if you are prescribed any medicines.

Pregnancy and the progestogen-only pill

If I become pregnant

There is a very slight chance you will become pregnant even if you use the pill correctly. However, a missed period does not always mean you are pregnant, especially if you have used the pill correctly.ª Take the next packet as normal if you think you have put yourself at risk of pregnancy or if you miss a second period see your doctor at once.

It is unlikely that taking the pill during early pregnancy will increase the risk of defects in the fetus. However, the likelihood of ectopic pregnancy is greater if you become pregnant while taking the progestogen-only pill. Although it is rare, it can be dangerous. You should see your doctor straightaway if you have sudden unexplained lower abdominal pain.

If I want to become pregnant

You can try to get pregnant as soon as you stop taking the pill which you can stop taking at any time. It is helpful to stop the pill and then have at least one period before you try to get pregnant. You can use another method such as a condom for that time. This makes it easier to date when pregnancy more accurately and to start pre-pregnancy care such as taking folic acid.

However, if you do get pregnant immediately after stopping the pill, research to date has shown this is not harmful.

After childbirth

The Progestogen-only pill can be started any time after the birth. If you start the pill after day 21 you will need to use additional contraception for two days.

It is suitable for women who are breastfeeding as it does not reduce the milk flow.

A tiny amount of hormone enters the milk, but research suggests this will not harm the baby.

After an abortion or miscarriage

You can start taking the pill immediately after a miscarriage or abortion.