Do Antibiotics Affect Birth Control Pills? Your Options - Obstetrics and Gynecology

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Emergency contraceptive pills and antibiotics?


I have been taking the oral contraceptive pill continuously for five months.
Today is the fourth pill of my new pack, but due to an upper respiratory infection, I have taken other medications, including PHENEXPECTACETAMOLLYSOZYMEBPPAMOXYCILLIN (eight pills over two days).
Will these medications affect the efficacy of my contraceptive pill? If I stop taking these medications, will it take a week to restore the effectiveness of the oral contraceptive, or has its contraceptive effect already been lost?

Shirley, 20~29 year old female. Ask Date: 2019/06/17

Dr. Huang Jianzhong reply Obstetrics and Gynecology


I have been taking the oral contraceptive pill for five consecutive months.
Today is the fourth pill of my new pack, but due to an upper respiratory infection, I have taken other medications, including PHENEXPECTACETAMOLLYSOZYMEBPPAMOXYCILLIN (eight pills over two days).
Will these medications affect the efficacy of my contraceptive pill? Answer: These medications will not affect the efficacy of the contraceptive pill.
If I stop taking these medications, will it take a week to restore the efficacy of the contraceptive pill, or has the contraceptive effect already been lost? Answer: These medications do not affect the efficacy of the contraceptive pill.

Reply Date: 2019/06/17

More Info


When it comes to the interaction between antibiotics and birth control pills, it's essential to understand the nuances involved. Generally, most antibiotics do not significantly affect the efficacy of hormonal contraceptives like birth control pills. However, there are exceptions, and the specific medications you mentioned warrant a closer look.

The primary concern with antibiotics and birth control pills arises from the potential for certain antibiotics to reduce the effectiveness of hormonal contraceptives. The most commonly cited antibiotic in this context is rifampin, which is used to treat tuberculosis and other serious infections. Rifampin can induce liver enzymes that metabolize hormonal contraceptives, leading to reduced levels of these hormones in the bloodstream and, consequently, a decreased contraceptive effect. However, the antibiotics you mentioned—phenylephrine, acetaminophen, lysozyme, and amoxicillin—are not known to have this effect.

Amoxicillin, a commonly prescribed antibiotic for bacterial infections, has been studied extensively, and the consensus is that it does not significantly interfere with the effectiveness of birth control pills. The same applies to other antibiotics that are not in the rifampin class. Therefore, if you have taken amoxicillin for your upper respiratory infection, it is unlikely that it will affect your birth control pill's efficacy.

Regarding the timing of when to resume full contraceptive effectiveness after stopping antibiotics, since the antibiotics you mentioned do not interfere with hormonal contraceptives, you do not need to wait a week after stopping them to regain full contraceptive protection. You can continue taking your birth control pills as directed without concern for reduced efficacy due to the antibiotics you've taken.

It is important to note that while antibiotics may not affect hormonal contraceptives, other factors can influence their effectiveness. For example, if you experience vomiting or diarrhea as a side effect of the antibiotics or due to the infection itself, this could potentially impact the absorption of the birth control pill. In such cases, it is advisable to use a backup method of contraception, such as condoms, until you are sure that your birth control pill is being absorbed effectively.

In summary, the antibiotics you mentioned are not known to affect the efficacy of your birth control pills. You can continue taking your contraceptives as prescribed without needing to wait for a week after stopping the antibiotics. However, always consult with your healthcare provider if you have specific concerns or if you are prescribed a new medication, as they can provide personalized advice based on your medical history and the medications you are taking.

Lastly, if you have any further questions or concerns about your birth control method or the medications you are taking, do not hesitate to reach out to your healthcare provider for clarification and guidance. They can help ensure that you have the most accurate and relevant information for your situation.

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