Does Cephalexin Affect the Effectiveness of Yaz Birth Control?

Yuezi and Antibiotics

Hello, I am currently taking the oral contraceptive Yaz (I am on the eighth pill of this pack) and have recently been diagnosed with a urinary tract infection.
I am taking the antibiotic cephalexin.
I would like to know if taking this antibiotic will reduce the effectiveness of Yaz.
If it does reduce its effectiveness, I have engaged in unprotected intercourse during what seems to be my fertile window in the past couple of days.
What remedial measures can I take? Thank you!

Lucy, 20~29 year old female. Ask Date: 2021/12/27

Dr. Zhang Kunmin reply Obstetrics and Gynecology

Hello,
The medications that may interact with oral contraceptives include:
1.
Antibiotics (Penicillin, Cephalosporins, Erythromycin, Sulfonamides, Bactrim, Chloramphenicol).
Doxycycline can reduce the effectiveness of oral contraceptives, and when taking doxycycline, alternative contraceptive methods should be employed, as it may decrease the gut flora that aids in absorption, thereby reducing the effectiveness of the contraceptive.
2.
Sedatives (Barbiturates) - increase the metabolism of contraceptives, reducing their effectiveness.
3.
Antiepileptic drugs (Primidone, Phenytoin, Carbamazepine) - increase the metabolism of contraceptives, reducing their effectiveness.
4.
Tuberculosis medications (Rifampicin, Isoniazid).
5.
Antidiabetic medications (Rosiglitazone).
6.
Acetaminophen and Ascorbic acid (Vitamin C) - may inhibit the metabolism of estrogen, potentially increasing its concentration in the body and leading to a higher incidence of side effects.
7.
Oral contraceptives can affect the action of anticoagulants.
8.
Smoking - increases the metabolism of contraceptives, reducing their effectiveness.
It is recommended to consider emergency contraception for added protection.
If there is no expected withdrawal bleeding, pregnancy should be suspected.

Thank you! Wishing you peace and health.

Dr.
Zhang

Reply Date: 2021/12/27

More Info

When it comes to the interaction between antibiotics like Cephalexin and hormonal contraceptives such as Yaz, it's important to understand how these medications work and their potential effects on each other. Yaz is a combination oral contraceptive that contains estrogen and progestin, and it is designed to prevent ovulation, thicken cervical mucus, and thin the uterine lining to prevent pregnancy.

The concern about antibiotics affecting the effectiveness of birth control primarily stems from the interaction of certain antibiotics with the liver enzymes that metabolize hormonal contraceptives. However, Cephalexin, which is a cephalosporin antibiotic, has not been shown to significantly impact the effectiveness of hormonal contraceptives like Yaz. Most studies indicate that common antibiotics, including Cephalexin, do not reduce the effectiveness of birth control pills.

That said, there are a few important considerations to keep in mind:
1. Gastrointestinal Issues: If you experience gastrointestinal side effects from Cephalexin, such as vomiting or diarrhea, this could potentially affect the absorption of Yaz. If you vomit within two hours of taking your birth control pill, it may not be fully absorbed, and you may need to take another pill.

2. Timing and Consistency: It's crucial to take your birth control pill at the same time every day to maintain its effectiveness. If you miss a dose or take it late, this could increase the risk of unintended pregnancy, regardless of whether you are taking antibiotics.

3. Emergency Contraception: If you have had unprotected intercourse during what you believe to be a "dangerous" period (the time when you are most fertile), and you are concerned about the effectiveness of your birth control, you may consider using emergency contraception. Options include Plan B (levonorgestrel) or Ella (ulipristal acetate), which can be taken after unprotected sex to help prevent pregnancy.

4. Consult Your Healthcare Provider: It is always best to discuss any concerns about medication interactions with your healthcare provider. They can provide personalized advice based on your medical history and current medications.

In summary, while Cephalexin is not known to reduce the effectiveness of Yaz, it is essential to be aware of how gastrointestinal side effects can impact absorption. If you have concerns about potential pregnancy due to unprotected intercourse during this time, consider consulting your healthcare provider for further guidance and possible emergency contraception options. Always prioritize open communication with your healthcare provider regarding any medications you are taking and their potential interactions.

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