Missed Birth Control Pill: Risk of Pregnancy and Antibiotic Effects

Missed a dose of the emergency contraceptive pill on the fifth day and took it more than 12 hours later?

I have been taking the contraceptive pill for over six months.
This month, I started a new pack, taking the first pill on December 28 at around 11:00 PM.
I missed the fifth pill on January 1 and took it the next day around 2:30 PM.
After that, I remembered to take the pills regularly.
On January 3, I had unprotected intercourse but there was no ejaculation inside.
I am also currently taking antibiotics for a dermatological issue.
I would like to know if there is a possibility of pregnancy in this situation and whether the antibiotics could affect the effectiveness of the contraceptive pill.
Thank you.

Ms. Li, 20~29 year old female. Ask Date: 2022/01/03

Dr. Zhang Kunmin reply Obstetrics and Gynecology

Hello, when you forget to take your birth control pill, you should take it as soon as you remember, and continue taking the next pill at the regular time.
If you miss taking an effective pill for more than 12 hours, in addition to taking the missed pill, it is advisable to use an additional barrier method of contraception for seven days.
If you miss more than 24 hours, you should stop taking the current birth control pills for seven days (including the days you missed) and then continue with the next cycle.
If you miss a pill and do not experience expected withdrawal bleeding during the subsequent pill-taking period, you should suspect the possibility of pregnancy.
Medications that may interact with oral contraceptives include:
1.
Antibiotics (Penicillin, Cephalosporins, Erythromycin, Sulfonamides, Bactrim, Chloramphenicol).
Doxycycline may reduce the effectiveness of oral contraceptives, as it can decrease the gut flora that aids in absorption, thereby reducing the effectiveness of the pills.
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, leading to increased serum levels and 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.
Thank you! Wishing you safety and health.
Dr.
Zhang

Reply Date: 2022/01/03

More Info

When it comes to missed birth control pills and the potential risk of pregnancy, it’s important to understand how hormonal contraceptives work and the implications of missing a dose. Birth control pills are designed to maintain consistent hormone levels in the body to prevent ovulation. If you miss a pill, especially during the first week of a new pack, the risk of ovulation increases, which can lead to pregnancy if you engage in unprotected intercourse.

In your case, you mentioned that you missed the fifth pill in your pack and took it the next day. According to most guidelines, if you miss a pill and take it within 24 hours, you should still be protected from pregnancy. However, since you had unprotected sex on January 3rd, it’s crucial to consider the timing of your missed pill. The general recommendation is that if you miss a pill in the first week and have unprotected sex, you may want to consider emergency contraception, especially if you are concerned about the risk of pregnancy.

Regarding the use of antibiotics, it’s a common misconception that all antibiotics interfere with the effectiveness of birth control pills. Most antibiotics do not affect hormonal contraceptives. However, there are exceptions, such as rifampin and rifabutin, which can reduce the effectiveness of birth control pills. If you are taking a different antibiotic, it is unlikely to impact your birth control. Nonetheless, it’s always wise to consult with your healthcare provider or pharmacist about specific medications you are taking to ensure there are no interactions.

In summary, while there is a potential risk of pregnancy due to the missed pill, taking it within 24 hours mitigates that risk significantly. The use of most antibiotics does not typically affect the efficacy of birth control pills, but it’s essential to verify the specific antibiotic you are using. If you have concerns about pregnancy or the effectiveness of your birth control, consider taking a pregnancy test if your period is late, and consult your healthcare provider for personalized advice.

Additionally, if you find yourself frequently missing pills, it may be worth discussing alternative contraceptive methods with your healthcare provider. Options such as the patch, ring, or long-acting reversible contraceptives (LARCs) like IUDs can provide more consistent protection without the need for daily adherence. Always prioritize open communication with your healthcare provider regarding any medications you are taking and any concerns you may have about your reproductive health.

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