What medications interfere with birth control pills?

Birth control pills or oral contraceptive pills are a popular and effective form of contraception used by millions of women worldwide. However, it is essential to be aware that certain medications can interfere with the effectiveness of birth control pills, potentially leading to unintended pregnancies. In this article, we will explore the medications that can interfere with birth control pills and discuss the implications for women who are taking these medications.

Understanding Birth Control Pills

Before delving into the medications that can affect birth control pills, let’s first understand how these pills work. Birth control pills are a form of hormonal contraception that contains synthetic versions of the hormones estrogen and progestin. These hormones work in combination to prevent pregnancy by suppressing ovulation, thickening the cervical mucus to prevent sperm from reaching the egg, and thinning the lining of the uterus to make it less receptive to implantation. There are two types of birth control pills: combination pills and progestin-only pills.

Combination pills contain both synthetic estrogen and progestin hormones. These pills work by suppressing ovulation, thickening cervical mucus to prevent sperm from reaching the egg, and thinning the lining of the uterus to make it less receptive to implantation.

Progestin-only pills, also known as mini-pills, only contain the progestin hormone. These pills primarily work by thickening cervical mucus and altering the lining of the uterus to prevent fertilisation and implantation.

Medications that interfere with Birth Control Pills

It is crucial to be aware that certain medications can interfere with the effectiveness of birth control pills, potentially reducing their contraceptive efficacy. These medications can either increase the metabolism of the synthetic hormones in birth control pills or interfere with their absorption, rendering them less effective in preventing pregnancy.

Enzyme-inducing medications

One category of medications that can interfere with birth control pills is enzyme-inducing medications. Enzyme-inducing medications speed up the processing of contraceptive hormones in the body, leading to lower hormone levels and reduced effectiveness of birth control pills. Some common examples of enzyme-inducing medications include:

• Rifampicin-like antibiotics, such as rifampin, rifabutin, and rifapentine. These antibiotics are commonly used to treat various infections, including tuberculosis. It’s believed that these antibiotics increase the liver’s production of enzymes, which can accelerate the breakdown of hormones in the birth control pill, reducing concentrations of estrogen in the blood
• Anticonvulsant medications, which are used to treat conditions such as epilepsy, can also interfere with birth control pills. Drugs like phenytoin, carbamazepine, and phenobarbital have been shown to increase the liver’s production of enzymes, potentially reducing the levels of hormones in the body and making birth control pills less effective
• Antiretroviral drugs used in the treatment of HIV, such as efavirenz and nevirapine, can interact with birth control pills. These medications can increase the liver’s production of enzymes, leading to a potential decrease in the levels of hormones in the body and reducing the effectiveness of birth control pills
• St. John’s Wort is a popular herbal supplement used to treat depression and anxiety. However, it can also interfere with birth control pills. This herbal remedy has been found to induce liver enzymes, which can decrease the levels of hormones in the body and reduce the effectiveness of birth control pills

If you are taking any of these medications while using birth control pills, it is essential to consult your healthcare provider. They can guide you on alternative forms of contraception or recommend adjusting your medication regimen to ensure effective contraception.

Medications that affect absorption

Another group of medications that can interfere with the effectiveness of birth control pills are those that affect their absorption. These medications can alter the gastrointestinal environment or decrease the absorption of the synthetic hormones in birth control pills, potentially rendering them less effective in preventing pregnancy. Examples of such medications include:

• Some medications used to reduce levels of bile acid, such as cholestyramine
• Weight loss drugs such as orlistat, which can cause diarrhoea and affect the absorption of birth control pills

If you are taking any of these medications, it is crucial to discuss the potential interactions with your healthcare provider. They can guide you on how to ensure effective contraception while taking these medications, such as using additional forms of contraception or adjusting the timing of pill administration.

Other medications and considerations

In addition to enzyme-inducing medications and those that affect absorption, some other medications and considerations may impact the effectiveness of birth control pills. These include:

• Antibiotics: There is a common misconception that all antibiotics interfere with birth control pills. While some antibiotics, such as rifampin, do interact with birth control pills, most other antibiotics such as amoxicillin, trimethoprim and erythromycin do not have a significant impact on their effectiveness. However, it is always advisable to consult your healthcare provider for personalized advice
• Medications that affect liver enzymes: Certain medications that affect liver enzymes, such as some antifungal medications such as griseofulvin and nystatin and protease inhibitors used to treat HIV, may interact with birth control pills. It is important to discuss these potential interactions with your healthcare provider
• Individual variations: It is worth noting that individual variations in metabolism can also affect the effectiveness of birth control pills. Some women may naturally metabolize the synthetic hormones in birth control pills more rapidly, potentially reducing their contraceptive efficacy. If you have concerns about the effectiveness of your birth control pills, consult your healthcare provider for further evaluation

Ensuring effective contraception

To ensure effective contraception while taking medications that may interfere with birth control pills, consider the following:

• Consult your healthcare provider: Always consult your healthcare provider if you are starting any new medication or have concerns about potential interactions with your birth control pills. They can provide personalised advice based on your specific situation
• Use additional forms of contraception as a backup method: If you are taking medications that may interfere with birth control pills, using additional forms of contraception, such as condoms (barrier method) or a non-hormonal intrauterine device (IUD), which can provide an extra layer of protection against unintended pregnancies
• Timing and consistency: It is crucial to take your birth control pills at the same time every day and follow the prescribed regimen consistently. This helps maximize their effectiveness, even in the presence of potential interactions with other medications
• Consider alternative methods: If you are unable to use birth control pills due to medication interactions or other reasons, discuss alternative contraceptive methods with your healthcare provider. There are various options available, including long-acting reversible contraceptives (LARCs) like the contraceptive implant or IUDs

Conclusion

While birth control pills are a highly effective form of birth control, it’s important to be aware of potential drug interactions with other medications. Antibiotics, anticonvulsants, antiretroviral drugs, and St. John’s Wort are some examples of medications that can interfere with the effectiveness of birth control pills. Speak to a pharmacist or doctor who can help you decide which method of birth control is best for you. It is crucial to consult your healthcare provider if you are taking any of these medications, sharing any medical conditions, particularly high blood pressure and over-the-counter medications you may be taking. By being proactive and informed, you can make the best decisions for your reproductive health and well-being. Speak to a pharmacist or doctor who can help you decide which method of birth control is best for you.

Sources

• Which medicines affect my contraception? – NHS
• Contraceptives, interactions | Treatment summaries – BNF – NICE