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 late?

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, consistently after 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 did not ejaculate inside.
I am also currently taking antibiotics for a dermatological condition.
I would like to know if there is a possibility of pregnancy and whether the antibiotics could affect the effectiveness of the contraceptive pill.
Thank you.

Ms. Li, 20~29 year old female. Ask Date: 2022/01/04

Dr. Zhang Kunmin reply Obstetrics and Gynecology

Hello, when you forget to take your contraceptive pill, you should take it as soon as you remember and continue taking the next pill at the usual 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 a pill for more than 24 hours, stop taking the current contraceptive pill and refrain from taking it for seven days (including the days you missed), then continue with the next cycle.
If you miss a pill and do not experience the 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 can reduce the effectiveness of oral contraceptives, as it may decrease the gut flora that aids in absorption, thereby lowering the contraceptive effect.
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 estrogen metabolism, leading to increased concentrations in the body and a higher incidence of side effects.
7.
Oral contraceptives may 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: 2022/01/04

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, which prevents ovulation. Missing a pill can disrupt this hormonal balance, potentially leading to ovulation and, consequently, an increased risk of pregnancy.

In your case, you missed a pill on January 1st and took it the next day at 2:30 PM, which is within 24 hours of the missed dose. Most combination birth control pills allow for a grace period of up to 24 hours for taking a missed pill without significantly increasing the risk of ovulation. Since you resumed taking your pills as scheduled after that, the risk of pregnancy remains low, especially since you had sexual intercourse on January 3rd, which was after you had taken the missed pill.

However, it’s crucial to note that the effectiveness of birth control pills can be influenced by certain medications, particularly antibiotics. While most antibiotics do not affect the efficacy of hormonal contraceptives, there are exceptions. For instance, rifampin and rifabutin, which are used to treat tuberculosis and other infections, can significantly reduce the effectiveness of birth control pills. On the other hand, common antibiotics like amoxicillin or doxycycline generally do not have a significant impact on the effectiveness of birth control pills.

If you are taking an antibiotic that is known to interact with hormonal contraceptives, it is advisable to use a backup method of contraception, such as condoms, for the duration of the antibiotic treatment and for at least seven days after completing the course. If you are unsure about the specific antibiotic you are taking and its potential effects on your birth control, it is best to consult with your healthcare provider or pharmacist for clarification.

In summary, based on the information provided, the likelihood of pregnancy is low due to the timely resumption of your birth control pill after missing one. However, if you have concerns about the antibiotic you are taking and its interaction with your birth control, or if you experience any unusual symptoms, it is always prudent to consult with your healthcare provider for personalized advice and reassurance. They can provide you with the most accurate information based on your specific situation and the medications you are using.

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