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If you've got to take antibiotics and the pill together then it's understandable to worry about potential side effects – especially if your risk of pregnancy is going to increase.
Find out what the risk of taking these 2 medications together is and whether you need to do anything to protect yourself from them.
In most cases it's not a problem – usually when you have an infection or are ill your doctor will prescribe standard antibiotics and there is no real need to worry about interactions between these and your Pill. Both the progestogen-only (mini pill) and the combined contraceptive pill can be taken with broad-spectrum antibiotics.
Antibiotics can indirectly affect the Pill – if your antibiotics cause you to vomit or to have severe diarrhoea then this can stop your Pill from working. If you are ill within a certain time of taking your Pill, then it may not have been absorbed in time. Therefore, you should read the patient information leaflet found in the medication packaging to see what to do.
Make sure to mention your other medications during your assessment – if your doctor is going to prescribe you with antibiotics, let them know you’re on the Pill. Tell them which one you take or if you can, take the box with you to your appointment, that way your doctor will be able to check for any possible interactions. They should then advise you about what you can do to prevent pregnancy, whether that is changing your contraception method or if possible changing the antibiotics they have prescribed.
There are two antibiotics which are known to affect the pill directly – they are:
These antibiotics are not prescribed often and are used to treat and prevent tuberculosis (TB), meningitis and MRSA.
What to expect when starting antibiotics – antibiotics are often prescribed for the treatment or prevention of some bacterial infections. They don’t usually work for coughs, colds or sore throats and many mild bacterial infections clear up on their own. Although broad-spectrum antibiotics shouldn’t interact with your contraceptive pill, you may experience side effects from the antibiotics. Side effects can include:
Be aware of getting sick – if you are sick or have diarrhoea, you should read the leaflet of your contraceptive pill to see if its function will be affected. It is likely that if you are ill shortly after taking your pill, then it will not have been absorbed by the body. Therefore, it may not work effectively – read the instructions on the leaflet about what you should do if this is the case.
What to expect when starting the pill – likewise, if you begin to take the pill whilst on antibiotics, you may experience some side effects from the Pill. Side effects of taking the pill may include:
What to do about side effects from either – if you experience side effects from either your antibiotics or your pill, speak to your doctor or nurse for advice. Wait to speak to them before stopping your treatment.
The Pill should be working, even after taking antibiotics (as long as you haven't been sick) – but if you have had sex and you experience the following symptoms it is advisable to take a pregnancy test:
If you suspect you may be pregnant make an appointment to see your doctor or nurse. If pregnancy is confirmed they will talk you through your options.
Antibiotics can take some time to work – antibiotics get to work straight away by killing the bacteria causing your infection. Usually, a course of antibiotics is taken for 7 or 14 days. It can take up to a week for the effects of your infection begin to clear up. If you finish your course of antibiotics and you still feel the same or worse, consult your doctor for advice. It may be that you need a stronger dose or a different type of antibiotic.It could be the one you started taking most recently – if you think you are experiencing side effects, it is very likely they are being caused by the medication you started taking most recently. For example, if you have been taking the pill for a while but have only just started a course of antibiotics, it is likely the antibiotics are causing the effects.
It's not always easy to tell – if you began taking them around the same time it can be difficult to distinguish between the two as the side effects can be similar. The table below shows the similarities and differences between the side effects of both the pill and antibiotics:
| The Pill | Antibiotics |
|---|---|
| Nausea (feeling sick) | |
| Being sick | |
| Abdominal pain | |
| Headaches | |
| Mood changes | Rash |
| Low libido (sex drive) | Bloating |
| Weight gain | Swollen, black, or hairy tongue |
| Bleeding between periods | Vaginal itching/discharge |
| Missed periods | Diarrhoea |
How to confirm where the side effects are coming from – if you think you may be experiencing side effects from your contraceptive pill, antibiotics or both, you should consult your doctor. The similarities between the side effects of both medications can make it difficult for you to determine the cause. Your doctor, however, will be able to distinguish between the two and provide a solution to make you feel better.
Yes it can be risky – alcohol can pose risks to your health if you are taking antibiotics, the contraceptive pill or both. If you have been prescribed antibiotics it is sensible to avoid alcohol altogether as it can make you feel unwell. However, if you drink in moderation while taking antibiotics it is unlikely you will have any significant problems.
When to avoid drinking altogether – there are some antibiotics which you should avoid drinking alcohol altogether. They are:
Drinking alcohol with either one of these antibiotics can cause the following side effects:
You should avoid alcohol for the duration of the course of these antibiotics and for 48 hours after you stop taking metronidazole and 72 hours after tinidazole.
Risk of drinking when you take your pill – if you drink and it makes you sick within two hours of taking your contraceptive pill, your body may not have absorbed the pill. Therefore, this can also increase your chance of getting pregnant. If you are planning to drink, consider these factors:
Remember condoms are the only form of contraception which protects you and your partner from STIs
What else can affect the Pill or antibiotics? – if you take antibiotics or the contraceptive pill they may interact with other medications and substances, such as:
| The Pill | Antibiotics |
|---|---|
| Alcohol | |
| Each other (for some antibiotics only) | |
| Carbamazepine | Methotrexate |
| Phenytoin | Heparin |
| Phenobarbital | Warfarin |
| Primidone | Antifungal medication |
| St John's Wart | Diuretics |
| Muscle relaxants | |
| Nutritional supplements | |
| Non-steroidal anti-inflammatory drugs | |
Hoffmann, K. et al (2015). Oral contraceptives and antibiotics. A cross-sectional study about patients’ knowledge in General Practice. Reproductive Health; 12(43).
British National Formulary. (2018). Contraceptives, Interactions. NICE. [online]. Available at: https://bnf.nice.org.uk/treatment-summary/contraceptives-interactions.html [accessed 1st August 2018].
Simmons, K. B. et al (2018). Drug interactions between non-Rifamycin antibiotics and hormonal contraception: a systematic review. American Journal of Obstetrics and Gynaecology; 218(1): 88-97.
