Will This Antibiotic Interfere With My Birth Control?

Almost every day, pharmacists are asked whether taking antibiotics will interfere with birth control.

The issue of whether or not antibiotics interfere with the effectiveness of birth control has been a controversial topic for many years. To provide a quick review, there are many forms of birth control that contain both an estrogen and a progestin – pharmacists call these combined hormonal contraceptives.

Combined hormonal contraceptives include:

• The pill (Yaz, Tri-Sprintec, Cryselle, Heather, etc.)
• The patch (Ortho Evra)
• The ring (NuvaRing)

Combined hormonal contraceptives use multiple mechanisms to reduce the possibility of pregnancy. Estrogen suppresses the release of hormones from the pituitary. Progestin suppresses ovulation and thickens cervical mucus to prevent sperm from entering the upper genital tract. Progestin provides most of the contraceptive effects in hormonal contraceptive methods.

Broad-Spectrum Antibiotics and Common Antifungals = OK

Antibiotics routinely used to fight illnesses are the “broad-spectrum” antibiotics. These drugs are called “broad-spectrum” because they can be used to treat a variety of infections caused by many different organisms. These antibiotics include:

• Amoxicillin
• Azithromycin
• Clarithromycin
• Metronidazole
• Quinolones (ciprofloxacin, ofloxacin)
• Doxycycline

Common antifungal agents frequently used to treat vaginal yeast infections include:

• Fluconazole
• Miconazole

The Centers for Disease Control and Prevention (CDC) classifies broad-spectrum antibiotics and antifungals as category 1 interactions with contraceptives. This means that the CDC has determined that when using a broad-spectrum antibiotic or antifungal, there is no restriction to using them in combination with combined hormonal contraception. Many groups agree with the CDC, including the American College of Obstetricians and Gynecologists. Broad-spectrum antibiotics have not been found to reduce the concentration of hormones in the combined hormonal contraceptives to a sub-therapeutic level that could increase the risk of pregnancy. Therefore, a backup method of birth control is not required for women using combined hormonal contraceptives and broad-spectrum antibiotics. Even patients who may be on a long-term antibiotic, such as erythromycin for acne, will not require a backup method of birth control when taking both the antibiotic and their normal form of birth control.

Enzyme Inducers = Use a backup method

It is still important to ask your pharmacist about whether or not your antibiotic is considered “broad-spectrum,” because there are some antibiotics that do significantly interact with combined hormonal contraceptives.

Antibiotics that are known to definitely affect the efficacy of combined hormonal contraceptives are called “enzyme inducers” because they essentially make your body chew up the hormones in the birth control faster than normal. These types of antibiotics include the following:

• Rifampin (including some combination antibiotics that contain rifampin)
• Rifabutin
• Griseofulvin (used to treat fungal infections)

Rifampin, Rifabutin and griseofulvin are antibiotics known to reduce the levels of hormones in the pill, the patch or the ring. People on these antibiotics who also use combined hormonal contraception should use a backup method of birth control while they are taking these antibiotics. The CDC has classified these antibiotics as category 3 interactions with combined hormonal contraceptives because when used together, the effectiveness of the birth control is reduced and pregnancy risk is increased.