Do Antibiotics Affect Birth Control Pills? the Risks

I would like to ask if antibiotics can affect birth control pills?

I have been taking oral contraceptives for over a year.
My last menstrual period was on March 9.
On March 17, I visited a gynecologist due to discomfort in my lower abdomen, and the doctor prescribed erythromycin.
I had sexual intercourse on March 19.
I found online that erythromycin can affect the effectiveness of oral contraceptives, so I would like to know how high the chance of pregnancy is in this situation.
Additionally, I developed gastroenteritis on March 20 and went to the emergency room for IV fluids.
On March 21, I returned for diarrhea, and the doctor prescribed anti-nausea and anti-diarrheal medications.
Will this affect the effectiveness of my oral contraceptives? Thank you for your response.

S, 10~19 year old female. Ask Date: 2017/03/21

Dr. Liao Huiling reply Pharmacology

1.
There is currently no definitive literature reporting that erythromycin affects the efficacy of contraceptive pills and the potential risk of pregnancy.
2.
To confirm whether there are interactions between medications, please provide all drug components or names.
3.
If there are concerns about the impact of medications on the effectiveness of contraceptive pills during the treatment period, it is advisable to consider alternative contraceptive methods.

Reply Date: 2017/03/21

More Info

When it comes to the interaction between antibiotics and birth control pills, it is essential to understand the nuances involved. The concern that antibiotics may reduce the effectiveness of hormonal contraceptives, such as birth control pills, has been a topic of discussion among healthcare providers and patients alike.

The most commonly cited antibiotic that is known to potentially interfere with the effectiveness of birth control pills is rifampin, which is used to treat tuberculosis and some other infections. Rifampin can induce liver enzymes that metabolize hormones, leading to decreased levels of contraceptive hormones in the bloodstream. However, most other antibiotics, including erythromycin (the antibiotic you mentioned), do not have this effect. Studies have shown that the majority of antibiotics do not significantly impact the efficacy of birth control pills.

In your case, since you were prescribed erythromycin, the likelihood of it affecting your birth control pill's effectiveness is low. However, it is always prudent to consult with your healthcare provider about any medications you are taking, especially when it comes to contraceptive methods.

Regarding your sexual activity on March 19, if you were taking your birth control pills consistently and correctly before starting the antibiotic, the risk of pregnancy remains low. However, if you missed any doses or took the pills inconsistently, that could increase the risk of unintended pregnancy.

As for your gastrointestinal issues, medications for nausea and diarrhea can also have implications for the absorption of birth control pills. If you experienced vomiting within two hours of taking your pill, it is advisable to take another pill as soon as possible. Diarrhea can also affect absorption, particularly if it is severe or prolonged. If you are experiencing diarrhea, it is recommended to use backup contraception (such as condoms) until you are sure that your birth control pills are being absorbed effectively again.

In summary, while rifampin is a known antibiotic that can affect the efficacy of birth control pills, erythromycin is not typically associated with this issue. Your risk of pregnancy from the encounter on March 19 is likely low if you have been taking your pills correctly. However, gastrointestinal disturbances can complicate this situation, so monitoring your symptoms and consulting with your healthcare provider is crucial. If you have any further concerns about your contraceptive method or potential pregnancy, it is best to seek advice from a healthcare professional who can provide personalized guidance based on your medical history and current situation.

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