Introduction

Antibiotics and birth control are two commonly prescribed medicines that are crucial in maintaining health and well-being. Antibiotics, a class of drugs used to manage bacterial infections, including respiratory infections, Urinary Tract Infections, sexually transmitted diseases, and dental infections, have altered dramatically since their discovery. Thousands of antibiotics have been discovered, and providing an exact number is challenging.¹

On the other hand, birth control, particularly pills, contraceptive patches, birth control rings and implants, empowers individuals with reproductive choices. They alter the hormonal levels in women, including oestrogen and progesterone, which can significantly change the probability of pregnancy.²

While these medications serve a crucial purpose at an individual level, concerns have been raised regarding their potential when used in conjunction.

The question now lingers: "Can antibiotics affect the reliability of your birth control pills?". The answer is contingent on several factors, which we will discuss later in this article, and isn’t simply one-size-fits-all.

Grasp a regular situation where your doctor prescribes you a particular medication. They often do inquire about concomitant drugs that you're taking for a good reason. Some medicines may not work well when taken together. The same principle applies to hormonal birth control and antibiotics, which might affect their effectiveness. To minimise the risk of unintended pregnancies, researchers suggest taking extra precautions.

Concerns regarding the potential impact of antibiotics, specifically broad-spectrum antibiotics that target a wide range of bacteria, on hormonal contraceptives' efficacy have been present since 1973.³ The majority of antibiotics do not interfere with contraception. As outlined in a research study featured in the Journal of the American Academy of Dermatology, the consumption of widely prescribed antibiotics, such as ciprofloxacin, clarithromycin, doxycycline, metronidazole, roxithromycin, and temafloxacin, in conjunction with birth control pills does not lead to notable changes in hormone levels. The study implies that when these antibiotics are taken concurrently with oral contraceptives, there is no disruption to the crucial hormonal balance necessary for the effectiveness of birth control.⁴

Which antibiotics can impact the effectiveness of hormonal birth control?

Certain antibiotics influence hormonal birth control, while others do not. Yet, recent understanding and studies suggest that only a specific category of antibiotics, termed enzyme-inducing antibiotics, interacts with hormonal contraception, thus potentially reducing its effectiveness. Such examples include Rifampicin and rifabutin (up to some extent).⁴ These antibiotics fall into the same category and are commonly used to treat tuberculosis and meningitis.

If you find yourself taking "enzyme-inducing antibiotics" while using hormonal contraception, you need to take precautions to prevent unintended pregnancy.⁵ Hormonal contraception includes:

• The patch
• The implant
• The vaginal ring
• The pill⁷

Rifampin does not impact the effectiveness of certain contraceptives, including: 

• Progestogen-only injection
• Intrauterine device (IUD)
• Intrauterine system (IUS)

Rifampicin

Rifampin, classified as a rifamycin antibiotic and commonly prescribed for tuberculosis treatment, has the potential to diminish the effectiveness of birth control by lowering oestrogen and progestin hormone levels.

Rifabutin

Rifabutin (Mycobutin) is a rifamycin antibiotic. Commonly, rifabutin is included in a combination medication to treat stomach ulcers caused by Helicobacter pylori (H. pylori). It might also be used off-label for tuberculosis. While rifabutin can slightly lower oestrogen and progestin levels, reducing the effectiveness of birth control to some extent, this risk is generally lower compared to rifampin.

Mode of action

The major mechanism involved in the interaction includes the induction of cytochrome P450 enzyme in the liver. This leads to an elevated process of hepatic hydroxylation of estrogens. Rifampin and Rifabutin diminish the efficacy of oral contraceptives by reducing the levels of the birth control hormones, namely ethinyl oestradiol and progestin, which are crucial for preventing ovulation in women using these contraceptives.⁸ This decline in hormone levels is attributed to the drug’s ability to induce liver enzymes, hastening the breakdown of estrogen at an accelerated rate. Consequently, the lowered hormone levels can compromise the effectiveness of birth control.

Factors influencing the risk of pregnancy

Several factors can contribute to the risk and eventually impact the effect of antibiotics.⁹ This includes:

1. Type of Birth control pill
   1. The formulation of birth control pills plays a significant role in determining the potential risk. Specifically
   2. Low-Dose Pills: Birth control pills with lower hormone levels may present a slightly elevated risk compared to their higher-dose counterparts
2. Duration of Antibiotic Use
   1. The duration for which antibiotics are administered can influence the degree of impact on contraceptive efficacy. This includes two types of antibiotics
   2. Short-Term Use: Antibiotics prescribed for short-term treatments, such as infections, generally exhibit a lower impact on contraceptive effectiveness
   3. Long-Term Use: Prolonged antibiotic use, as seen in treatments like acne, introduces a different set of considerations and may pose a comparatively higher risk
3. Individual Health Factors
   1. Individual health factors can contribute to the overall risk equation. Considerations may include
   2. Metabolism and Absorption: Variations in metabolism and absorption rates among individuals can influence how antibiotics impact contraceptive efficacy
   3. Medical History: Pre-existing health conditions or a history of hormonal imbalances may influence how an individual responds to the combination of antibiotics and contraceptives
4. Personal Experience and Comfort Levels
   1. Personal experiences and comfort levels with contraceptives may influence decision-making:
   2. Past Pregnancy Incidents: Individuals with a history of getting pregnant while on birth control pills may opt for additional precautions when antibiotics are introduced
5. Specific Antibiotic Type:
   1. Different antibiotics interact with contraceptive methods in varying ways. Understanding the potential interactions associated with specific antibiotics is crucial
   2. Enzyme-Inducing Antibiotics: Certain antibiotics, such as rifampin and griseofulvin, are known to induce liver enzymes. This induction can accelerate the breakdown of hormonal components in birth control pills, potentially compromising their effectiveness

How can I avoid pregnancy while taking antibiotics?

Although the likelihood of pregnancy is generally low when combining antibiotics with birth control pills, it's challenging to determine individual risk levels.¹⁰ Newer birth control pills have fewer hormones to reduce side effects.

If you're on low-dose pills like-

• Alesse
• Aviane
• Cyclessa
• Levlite
• Loestrin 1/20
• Loestrin Fe 1/20
• Mircette

The pregnancy risk might be a bit higher when using antibiotics.

Some specific antibiotics need extra precautions, like using another birth control method or switching to a stronger pill.

If you're not comfortable with the pregnancy risk, especially if you've had bleeding or got pregnant while on pills before, add another birth control method (like condoms).

• For short-term antibiotics, like for an infection, use the second method during the antibiotic period and at least 7 days after
• If it's long-term, like for acne, use the extra method for at least two weeks after starting the antibiotics

The takeaway

In most cases, antibiotics don't seem to mess with birth control pills, except for one called rifampin. However, there's still uncertainty, and some doctors think more research is needed. To play it safe, it's a good idea to use a backup method like condoms while taking antibiotics, just to be extra sure. It's crucial to communicate openly with your healthcare provider about your contraceptive use and any medications you are taking. While antibiotics may generally pose little risk, being transparent about your overall medication regimen helps ensure optimal contraceptive protection and overall health. Remember to disclose all drugs, whether prescription, over-the-counter, or recreational, to your healthcare provider to facilitate informed and personalised medical decisions.

Summary

Antibiotics can potentially affect the effectiveness of birth control, but this is not typically the case for most antibiotics. The main concern is with "enzyme-inducing" antibiotics, like rifampin and, to a lesser extent, rifabutin, which can lower the levels of hormones in birth control pills by inducing liver enzymes that break down estrogen and progestin. This can reduce the effectiveness of hormonal contraceptives, such as pills, patches, and rings. However, methods like IUDs or progestogen-only injections are less effective. Factors like the type of birth control, duration of antibiotic use, and individual health conditions can influence the risk of pregnancy. To avoid unintended pregnancy, it’s recommended to use a backup contraceptive method, such as condoms, when taking antibiotics, particularly those known to induce liver enzymes. Always consult your healthcare provider to discuss your medications and contraceptive options.