Do Antibiotics Affect Birth Control Pills? What to Know About Emergency Contraception

Is it necessary to take emergency contraception?

Hello, doctor.
I would like to ask if antibiotics can affect the effectiveness of birth control pills.
I am currently taking birth control pills due to a urinary tract infection, and I have not experienced severe diarrhea during the course of taking the medication.
However, sometimes the timing of taking the birth control pills and antibiotics does not have a significant gap of a few hours.
I would like to know if this could impact the contraceptive effectiveness.
My menstrual period started on February 11 and ended on February 17.
I was supposed to start the next pack on February 15, but I delayed it until February 20 to adjust my menstrual cycle.
I had unprotected intercourse on February 19.
Should I take emergency contraception? I am unsure if I can take both preemptive and emergency contraception together, or if the preemptive method is still effective and I can continue with the second pack of birth control pills until my next period.
Thank you.

shin, 20~29 year old female. Ask Date: 2018/02/20

Dr. Huang Jianzhong reply Obstetrics and Gynecology

Due to urinary tract infection, I have been taking birth control pills.
During the course of taking the medication, I did not experience severe diarrhea, but sometimes the timing of taking the birth control pills and antibiotics was not spaced out by several hours.
I would like to know if this affects the effectiveness of the contraception.

Answer: It will not affect the effectiveness of the contraception.
My menstrual period started on February 11 and ended on February 17.
I was supposed to start the next pack on February 15, but I delayed taking the second pack until February 20 to adjust my menstrual cycle.
I had unprotected intercourse on February 19.
Should I take emergency contraception?
Answer: There is no need to take emergency contraception.
I am unsure if taking both pre- and post-coital contraception together is effective, but it seems that the pre-coital contraception remains effective, and there is no need to take emergency contraception.
Should I just continue taking the second pack of birth control pills until my next menstrual period?
Answer: Yes, you should continue taking the second pack of birth control pills.

Reply Date: 2018/02/20

More Info

Antibiotics and their interaction with birth control pills is a common concern among women who rely on hormonal contraceptives for pregnancy prevention. The general consensus in the medical community is that most antibiotics do not significantly affect the efficacy of birth control pills. However, there are exceptions, and understanding these nuances is essential for effective contraceptive use.

The primary antibiotic that has been shown to potentially interfere with hormonal contraceptives is rifampin, which is used to treat tuberculosis and some other infections. Rifampin can decrease the effectiveness of birth control pills by increasing the metabolism of the hormones in the liver, leading to lower hormone levels in the bloodstream. Other antibiotics, such as amoxicillin or doxycycline, have not been shown to have a significant impact on the effectiveness of birth control pills, especially if there are no gastrointestinal side effects like severe diarrhea or vomiting.

In your case, since you mentioned that you have not experienced severe diarrhea while taking antibiotics, it is likely that your birth control pills remain effective. However, it is always a good practice to take medications at different times to minimize any potential interactions, even if the risk is low.

Regarding your menstrual cycle and the timing of your birth control pills, it is important to follow the prescribed regimen as closely as possible. If you started your second pack of pills later than the recommended time, it could potentially affect your contraceptive coverage. Since you had unprotected intercourse on February 19, and you were not on the pill as directed, there is a risk of pregnancy. In such cases, emergency contraception (EC) can be considered. EC is most effective when taken as soon as possible after unprotected intercourse, ideally within 72 hours, but some forms can be effective up to five days after.

You can take emergency contraception alongside your regular birth control pills. However, it is crucial to continue taking your birth control pills as scheduled after taking EC. The emergency contraceptive will not affect the ongoing effectiveness of your regular contraceptive method once you resume taking it correctly.

In summary, while most antibiotics do not affect the efficacy of birth control pills, it is wise to be cautious and take them at different times. Given your situation with unprotected intercourse, it would be prudent to consider taking emergency contraception to reduce the risk of unintended pregnancy. Always consult with your healthcare provider for personalized advice and to discuss any concerns regarding your medications and contraceptive methods. They can provide you with the most accurate information based on your specific circumstances and health history.

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