Antibiotics and The Pill: What’s The Truth?

Reviewed: October 4, 2021
antibiotics and the pill
Another million dollar question many women find themselves asking. If you are on contraception and find yourself prescribed antibiotics, you might wonder whether one might affect the other.

It’s a tiny pill that packs a mighty contraceptive punch. But what happens when the pill and antibiotics interact? Let’s take a look at the effects of the interaction on the pill as a contraceptive.

TL;DR: what’s the lowdown?

  • Most (but not all) antibiotics are non-enzyme-inducing which means your contraceptive pill will continue to work just fine
  • But… some can cause vomiting or diarrhoea which you might also experience due to the illness itself – this can affect the absorption of your pill
  • Enzyme inducing antibiotics such as rifampicin or rifabutin can make some forms of contraception including the pill less effective
  • Before starting a new medicine ask the health professional that prescribed it whether it will impact upon your pill⁠
  • In the rare case you are prescribed an enzyme inducing antibiotic, to make sure you’re protected you could switch to an IUD, IUS or the injection – or temporarily use barrier methods such as condoms
  • Once you have completed your course of these antibiotics, you must continue to use any alternative contraceptive method for 28 days

 

The routine nature of the pill means taking it daily can be a well-versed habit and a somewhat subconscious ritual. So much so that, if we find ourselves needing other medication, we often don’t even think of the pill as meds we are already taking. 

But it’s important to remember that just like any other drug, over the counter or prescription, there are always possibilities of interactions. Antibiotics are no exception and an unplanned pregnancy as a side effect is possibly one we’d rather avoid! 

So, it’s important to be clued up on the facts about antibiotics and the pill, and most importantly, the effects they can have on the pill’s ability to prevent pregnancy.

What are antibiotics and why are they prescribed?

Antibiotics are used in the treatment of bacterial infections. Generally speaking, they are prescribed for infections that are severe in nature, where there is a risk of more serious complications, in patients where symptoms are unlikely to improve on their own, or where there is a risk of infecting others. Antibiotics are not used to treat viral infections; for this they are ineffective.

Antibiotics can be prescribed for many common conditions; persistent UTIs, acne, or genital herpes can all require their use. They can also be used as a preventative step where there is a future risk of infection. This can include certain types of surgery, such as the removal of the appendix or breast implant surgery, or a bite or wound that has a high chance of becoming infected. Less common illnesses, such as tuberculosis, will also use antibiotics in prevention and treatment.

I’m taking antibiotics; will they affect my pill?

To answer this we need to look a little more closely at the science. Rifampicin and rifabutin are two antibiotics known as enzyme-inducing antibiotics. This means they can increase the enzymes in your body. Subsequently, this increases the metabolism of oestrogens and progestogens, the hormones contained within the combined pill that work to prevent pregnancy. The result is a direct hit on its efficacy.

All other antibiotics are non-enzyme-inducing, and these will not have any effect on the pill. There is no compromise in efficacy and no other precautions regarding contraception are required. The good news is most antibiotics commonly prescribed are non-enzyme-inducing, and your pill will continue to work just fine. Phew!

It is worth noting, however, that while these antibiotics may not directly impact the efficacy of the pill, other side effects may create issues. Antibiotics of any type can cause vomiting or severe diarrhoea. You may also be experiencing these symptoms due to the illness itself. 

If this happens, and you are sick within 2 hours of taking the pill, absorption of the contraceptive pill may be affected and it will be necessary to take another pill right away. Sickness or diarrhoea lasting more than 24 hours will impact the level of protection against pregnancy and it is important to remember the validity of the pill as a contraceptive cannot be guaranteed. Each day of sickness or diarrhoea should be counted as a missed pill day. If possible, try to continue to take your pills as normal and use condoms as an extra form of contraception.

Whether you’re taking antibiotics or not, this information is important to remember. Vomiting with any cause, due to illness or as the result of an almighty hangover, can still impact the absorption of the pill!

Do antibiotics affect the mini-pill?

The progestogen-only pill, or mini-pill, will be affected in the same way as the combined pill, as will the implant, patch and vaginal ring. Rifampicin or rifabutin – enzyme-inducing antibiotics – will compromise the efficacy of the mini-pill due to the increase in the metabolism of the progestogen. All other antibiotics (non-enzyme-inducing) will not affect the mini-pill.

So, my antibiotics are affecting my pill. What should I do?

First off, don’t panic; there are multiple options available. Depending on personal preference and duration of the course of antibiotics, there are several choices. The progestogen-only injection, an intrauterine system (IUS), and an intrauterine device (IUD) are all unaffected by enzyme-inducing antibiotics. 

You can switch to one of these methods temporarily, or you may wish to make a change on a more permanent basis. The Lowdown’s contraception reviews are a great way to assess these alternatives and make an informed decision. With options to search for reviews based on side effects, both positive and negative, it’s an excellent way to access real-world responses to a variety of contraceptives. You can also find out more about switching contraception in this guide.

Condoms are also an alternative that can be used alongside the pill. If you wish to continue using your current hormonal contraception and the course of antibiotics is less than 2 months, it is important to discuss this with your doctor. You may be advised to take the pill in a different way, whilst also using condoms.

How long do enzyme-inducing antibiotics affect the pill?

Once you have completed the course of these antibiotics, you must continue to use any alternative contraceptive method for 28 days. You may wish to switch back to your previous method, but be sure to continue with a method unaffected by antibiotics for those full 4 weeks before doing so.

Can you take the morning-after pill while on antibiotics?

The emergency contraceptive pills Levonelle and ellaOne both work to prevent pregnancy by stopping or delaying ovulation, the process in which an egg is released from the ovaries. For those taking commonly used antibiotics, the morning-after pills will work just fine. 

But, just as the combined pill, mini-pill and other hormonal contraceptives are affected by enzyme-inducing antibiotics, the morning-after pill will be, too. It’s not recommended that you use the morning-after pill if you are taking rifabutin or rifampicin, due to the impact on its ability to prevent pregnancy. 

There is, however, an alternative to the morning-after pill. An intrauterine device (IUD) can be used as a form of emergency contraception. This has no interaction with antibiotics and the IUD is actually more effective than emergency contraceptive pills, with less than 1% of women becoming pregnant whilst using the IUD.

One last thing about antibiotics and the pill

Enzyme-inducing antibiotics are not commonly prescribed. They are used in the treatment and prevention of tuberculosis and meningitis. Most antibiotics used for common conditions, such as chest infections or UTIs, will be non-enzyme-inducing and will therefore have no bearing on the efficacy of your contraception. 

Patient Information Leaflets (PIL) can be contradictory with their advice and may relay information that is outdated in regards to this issue. So, it’s important to remember which antibiotics will affect your contraception and the options available to you. If you are ever in doubt, speak with your doctor or pharmacist.

Sources:

FSRH:

https://www.fsrh.org/blogs/myth-antibiotics-stop-combined-hormonal-contraception-from/

NHS:

https://www.nhs.uk/conditions/contraception/antibiotics-contraception/

https://www.nhs.uk/conditions/antibiotics/uses/

https://www.nhs.uk/conditions/contraception/emergency-contraception/

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