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When it comes to preventing pregnancy through oral contraceptives, people can worry that taking all antibiotics can cancel out/nullify the protection offered by birth control....
When it comes to preventing pregnancy through oral contraceptives, people can worry that taking all antibiotics can cancel out/nullify the protection offered by birth control. However, in reality, only certain antibiotics of the Rifamycin family (which are often used to treat tuberculosis) significantly lower the effect of birth control. They do this by increasing the activity of liver enzymes and breaking down the hormones in the contraceptive that provide protection from pregnancy.
While other antibiotics don’t necessarily act in this way and reduce the effectiveness of birth control, they may cause severe vomiting or diarrhoea (Lasting more than 24hours) in rare cases. Oral contraception taken during this time would hence be rendered ineffective due to being removed from the body before it could be absorbed. In these situations, it is best to treat it as a “Missed pill” situation.
Aside from antibiotics, there are other medicines such as; anti-seizure medication or anti-HIV medication, which can impact the effectiveness of birth control. If you are on any type of birth control and starting a new medicine (including antibiotics), please consult with your doctor regarding unintended drug interactions.
You can now buy General Health Medicines (such as antibiotics) or Female Health medicines (such as contraceptive pills) from Meds For Less and expect easy, reliable and confidential delivery to your home address within 24 hours.
The interaction between antibiotic and birth control is important because certain antibiotics can lower the effectiveness of hormonal birth control by increasing their breakdown. This increases the risk of an unwanted pregnancy.
Most hormonal contraceptive options like the patch, pill, ring work by increasing hormone levels of oestrogen, progesterone or both in the body. These contraceptive options prevent pregnancy by:
Most antibiotics do not interfere with contraception and its effectiveness, however some antibiotics such as rifampicin (which are used to treat tuberculosis) and other similar antibiotics speed up how the liver breaks down contraceptive hormones. This lowers the necessary hormone levels in the body and hence reduces the efficacy of contraception.
The overall effect of this lowering of this hormonal imbalance is a chance of breakthrough ovulation and hence unwanted pregnancy.
A common misconception is that all antibiotics lower the efficacy of contraception. The main types of antibiotics that lower contraceptive efficacy are rifampin type drugs such as Rifampicin or Rifabutin. These antibiotics are normally used for the treatment of tuberculosis and related infections.
If you are concerned about antibiotics birth control pills interaction and the impact on the effectiveness of your hormonal contraception, then please consult with your healthcare provider.
Only a very small group of specific antibiotics have been proven to reduce the effectiveness of hormonal birth control. The main antibiotics which do so are described in the table below:
| Antibiotic | Used for | How these antibiotics reduce birth control effectiveness |
| Rifampicin | Tuberculosis and infections by other related bacteria (in the same myobacterial family)
Some infections by meningococcal bacteria (such as meningitis) |
Induces certain liver enzymes such as CYP3A4 and hence increases the breakdown of the hormones raised by the contraceptive pill. |
| Rifabutin | Tuberculosis and other related infections
(Especially in immunocompromised patients) |
|
| Rifapentene | Tuberculosis |
Some important points to clarify include the following:
If you are taking hormonal contraceptives and considering starting on/being started on any new medicines – please consult your healthcare provider about your full medication history (including contraception).
The following is an overview of how to avoid unintentional pregnancy while using antibiotics (especially enzyme inducing ones).
To start off with , you may wish to identify the antibiotic you are using and the level of risk it has at lowering hormonal contraceptive effectiveness. The risk is slightly higher with Rifampicin, rifabutin or rifapentin and lower with almost all other antibiotics (aside from the indirect effects of vomiting or diarrhea).
If you feel that you are at high risk of unplanned pregnancy with the antibiotics you are taking, then it may be advisable to use condoms or other barrier methods of contraception during your antibiotic treatment and for 4 weeks afterwards.
If the antibiotics you are taking are not high risk, but there has been episodes of vomiting and diarrhea (especially 1-2 hours after taking oral contraceptives) – treat it like a missed pill situation.
During your antibiotic use period, you may also wish to consider long term non-hormonal contraceptive options such as the Copper IUD, the Hormonal IUS or the Depo Injection. These methods of contraception bypass normal body metabolism and hence don’t rely on the Liver. This in turn reduces the chance that they would be affected by liver inducing antibiotics.
It is advisable to always check how any new medicine will interact with any contraception you are taking. The best source of advice and help would be your regular healthcare provider.
For most antibiotics, you will not need to stop and restart the pill after antibiotics, you can just continue taking it as scheduled. The only time that stopping/ restarting would be necessary is with Rifamycin type antibiotics (like Rifabutin, Rifampicin or Rifapentene).
If the antibiotic you are taking is not a Rifamycin type antibiotic, keep taking your contraceptive pill at the same time everyday. Avoid restarting or stopping your pack of contraceptive pills abruptly as this can disrupt the hormonal cover and lead to unintentional pregnancy. If you experience any vomiting or diarrhoea for more than 24 hours, or within 1-2 hours of taking your contraceptive pill, it is best to treat it like a missed pill situation.
If the antibiotic you are taking is a Rifamycin type antibiotic, keep taking your pill as scheduled and consider using backup contraceptive options like the male condom or the female diaphragm over the course of your antibiotic prescription and for 4 additional weeks afterwards.
If you are unsure about a medicine (antibiotic or not) interacting with your birth control, you can do some of the following things to ensure the safest approach.
Consult with your pharmacist or regular healthcare provider (usually GP) regarding your birth control method and how any new medications you are considering starting will interact with the contraception.
Additionally, you may also consider using back-up contraceptive alternatives such as condoms while taking antibiotics. This avoids any gaps in protection offered by the pill if the antibiotic does lower the pill’s effectiveness.
If there is any drug you are considered about/ know will interact with hormonal contraception, consider switching to a non-interacting contraceptive method long term, such as:
These methods bypass the metabolic pathway affected by enzyme inducing drugs (such as rifampin type antibiotics) and have lower chances of affecting contraception efficacy.
When you are on hormonal birth control and about to start taking antibiotics, it is natural to have some questions regarding the drug interaction and overall hormone effectiveness.
Some questions you could ask your doctor or pharmacist before starting antibiotics include:
This list is by no means exhaustive – if you have any questions of your own, please ask your doctor to ensure you are satisfied with the medicines you are taking and their interactions with one another.