Can antibiotics reduce the effectiveness of birth control pills?

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New research shows that antibiotics can reduce the effectiveness of birth control pills. So should a backup method of birth control (such as condoms) be used while you are taking antibiotics and a hormonal contraceptive?

1. Will antibiotics affect the effectiveness of birth control pills?

For years, women have been advised that their birth control might become less effective if they also take a course of antibiotics at the same time. The usual advice from doctors is to add another form of birth control to birth control (such as a condom), and possibly for 7 days after finishing antibiotics, to help prevent pregnant.
Today, most studies state that antibiotics, with the exception of the tuberculosis drug rifampicin (also known as Rifadin and Rimactane) and possibly other rifamycins such as rifabutin, do not change the effectiveness of the drugs. Hormonal form of birth control such as the pill. However, the scientists argue that many studies lack data on drug interactions and therefore are unlikely to detect occasional interactions.
In contrast, a large observational database study from BMJ Evidence-Based Medicine published in August 2020 found a possibility of pregnancy with a combination of birth control and antibiotics. However, this study could not demonstrate cause and effect based on the retrospective design and limitations of the study.
Because many current studies are conflicting, you should discuss this topic with your doctor if you are prescribed antibiotics while you are using a form of hormonal birth control.

2. Current studies on the effect of antibiotics on oral contraceptives

According to Dr. Mitchell Kramer, of Northwell Health's Huntington Hospital in Huntington, New York, some antibiotics will affect the metabolism of contraceptive hormones. Therefore, they recommend that patients who are taking oral contraceptives use additional methods of contraception, such as condoms or spermicides, for the duration of the antibiotic period as a precaution. . In August 2020, researchers from the United Kingdom published an observational study in the BMJ Journal of Evidence-Based Medicine, arguing that previous studies on interactions between antibiotics and oral contraceptives pregnancy has yielded mixed results. To clarify, Ferner and his team followed up on reports of adverse drug events that were reported by healthcare professionals and patients to the UK's Medicines and Medical Devices Regulatory Authority. Older brother. Specifically, they compared the number of unintended pregnancies to about 75,000 adverse events for antibiotics in general, about 33,000 for enzyme inducers, and more than 65,500 other drugs. There were 46 unintended pregnancies in antibiotic adverse drug reports (incidence 62 per 100,000), 39 in enzyme inducer reports (119 per 100,000), and 6 in reports on other drugs. The researchers found that people taking antibiotics were seven times more likely to have an unwanted pregnancy than other unrelated drugs. Unintended pregnancies were also 13 times more common in reports of enzyme inducers, including some antibiotics. The researchers emphasize that calculating absolute risk from the data is not possible, and that risk exposure will vary from woman to woman, depending on her circumstances and psychophysiological status. However, most agree that if a woman is using hormonal contraceptives and an antibiotic, she should take extra precautions when taking a short course of an oral contraceptive. bacteria.

In clinical experience, health professionals believe that only one antibiotic - rifamycin (brand names: Rifadin and Rimactane) and to a lesser extent rifabutin - has been shown to make birth control pills less effective. than. Rifampicin reduces effectiveness by decreasing levels of birth control hormones (ethinyl estradiol and progesterone) in women taking oral contraceptives. This is the level of hormone needed to prevent ovulation. In addition, Rifampicin is an enzyme inducer in the liver, causing the breakdown of estrogen faster than normal. Decreasing hormone levels can decrease the effectiveness of your birth control. Rifampin may also decrease the effectiveness of the transdermal patch (Ortho Evra) and vaginal ring (NuvaRing), so a different form of birth control should be used with these products. A non-drug method of birth control - eg condoms, diaphragms or copper IUDs, for example, if used concomitantly with rifampin is recommended. Depo-Provera, the birth control pill, may be another option. A 2018 review published in the American Journal of Obstetrics and Gynecology concurs with this information. The researchers completed a review of multiple studies that met the criteria, seeking to determine whether interactions between non-rifampicin antibiotics and hormonal contraceptives would decrease or increase effectiveness. toxicity of either therapy. The authors found no evidence supporting the existence of drug interactions between hormonal contraceptives and antibiotics (excluding rifamycins). Of these, two studies found no difference in pregnancy rates among women using oral contraceptives with and without antibiotics. No difference in ovulation suppression or breakthrough bleeding was seen in any of the studies that combined hormonal contraceptives with any antibiotics. No significant reduction in the pharmacokinetic parameters of progestin or ethinyl estradiol occurred with the use of any of the antibiotics. From this, the authors concluded that most women did not experience a reduction in contraceptive efficacy when hormonal contraceptives and antibiotics were used concurrently (with the exception of rifamycins). A review from the Journal of the American Academy of Dermatology states that pharmacokinetic evidence demonstrates that oral contraceptive steroid levels do not change with the use of a combination of antibiotics, including: ampicillin, ciprofloxacin, clarithromycin, doxycycline, metronidazole, ofloxacin, roxithromycin, tetracycline

With the exception of rifampicin, the effect of other antibiotics on birth control pills has not been clearly proven, so if you are taking any antibiotics, use condoms as a backup method. room. Talk to your doctor about switching to another method of birth control (for example, a copper IUD or diaphragm) if you will be using antibiotics for a long time. You also need to know that the main reason why women get pregnant when using birth control pills is because they don't take them correctly. Birth control pills fail in at least 1% of cases under perfect conditions and up to 9% of cases using conventional pills, so take the pill as directed or stick to reliable birth control methods is the key to effective contraception. Other events, such as vomiting or diarrhea for more than 48 hours after taking the pill can also reduce the pill's effectiveness in preventing pregnancy.
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