Will antibiotics affect my contraceptive?
Rifampicin (Rifadin, Rimycin) and rifabutin (Mycobutin) are the only antibiotics that are thought to affect how well some hormonal contraceptives work. These antibiotics are usually only used to treat serious bacterial infections like tuberculosis and methicillin-resistant Staphylococcus aureus (MRSA), and for preventing meningitis (an infection around the brain or spinal cord).
Rifampicin or rifabutin can make contraceptives containing oestrogen and/or progestogen less effective by reducing the levels of these hormones in your bloodstream, which increases the chance of pregnancy.
Always ask a health professional for advice if you are using a hormone contraceptive and you will be taking rifampicin or rifabutin.
Which contraceptives may be affected?
Rifampicin or rifabutin may affect forms of hormone contraceptives including:
- combined pill (containing oestrogen and progestogen)
- progestogen-only pill
- implants (e.g. Implanon; a thin white plastic rod that releases progestogen when placed under the skin of upper arm).
- vaginal ring (e.g. NuvaRing; a soft plastic ring inserted into the vagina that releases oestrogen and progestogen).
Rifampicin or rifabutin is unlikely to affect the following forms of contraceptives:
- progestogen injection
- intrauterine device (IUD) (e.g. copper IUD devices, or Mirena, a small plastic device that releases progestogen)
- barrier methods (such as condoms or diaphragm).
Ask a health professional for advice as you may need to use extra contraceptive precautions while you are taking rifampicin or rifabutin (and after finishing the prescribed course) or you may need to change the type of contraceptive you are using.
What should I do if I am taking a hormone contraceptive?
If you are prescribed rifampicin or rifabutin and you’re taking a hormone contraceptive pill or using an implant or vaginal ring, you will need to use an extra contraceptive method (e.g. condoms or a diaphragm) while you are taking the antibiotic and for 28 days after finishing your prescribed course.
If you’re taking a contraceptive pill, you may be advised to keep taking an active pill throughout your course of rifampicin or rifabutin and for 7 days after you have finished taking your prescribed course.
If you need to take rifampicin or rifabutin for a long time (e.g. 2 months) your health professional may recommend that you use a contraceptive method that’s unlikely to interact with the antibiotic (e.g. IUD or progestogen injection). You will need to continue using this new method for at least 28 days after finishing your prescribed course.
What should I do if I have vomiting or diarrhoea?
If you are taking a hormone contraceptive pill and you have a stomach upset while you are taking an antibiotic or another medicine, ask your doctor or pharmacist for advice. This is because vomiting or severe diarrhoea that continues for 24 hours or longer may reduce the effectiveness of hormone contraceptives so you may need to use another contraceptive method.
If you vomit within 2 hours after taking an active contraceptive pill, take another active pill as soon as you can.
What should I do if I am taking rifampicin or rifabutin and need emergency contraception?
Ask a health professional for advice about a suitable emergency contraceptive method.
Phone for medicines information
Call the NPS Medicines Line on 1300 MEDICINE (1300 633 424) to get information about your prescription, over-the-counter and complementary medicines (herbal, ‘natural’, vitamin and mineral supplements) from a pharmacist. Your call will be answered by healthdirect Australia.
- Family Planning New South Wales: Antibiotics and the Pill
- Contraception: An Australian clinical practice handbook. Third edition. Published by Family Planning New South Wales, Family Planning Queensland, Family Planning Victoria. 2012.
- Faculty of Sexual and Reproductive Healthcare. Drug interactions with hormonal contraception. UK: FSRH, 2011.
- Rossi S, ed. Australian Medicines Handbook [online]. Adelaide:AMH. January 2012.