Antibiotics Cuts Effect of Birth Control?

For a long time the antibiotics were considered the great villains of women taking the pill. The lack of scientific studies exclusively developed to research the interaction between antibiotics and the pill, combined with occasional reports of oral contraceptive failure after the use of certain antibiotics, have helped to create, even within the medical profession, the myth that not could mix antibiotics and hormonal contraceptives.

Antibiotics and birth control pills
Antibiotics and birth control pills

Many doctors today feel uncomfortable to prescribe some antibiotics, such as amoxicillin, metronidazole and tetracycline, for women of childbearing age and use of hormonal contraceptives.

This alleged risk, however, was never based on robust scientific evidence, but in uncontrolled studies and unproven theories. For example, antibiotics such as ampicillin and amoxicillin were considered dangerous for those who took the pill just because there was a theoretical risk of a change in intestinal bacterial flora that would cause a reduction in the absorption of the hormones estrogen and progesterone by the intestines. Despite the theoretical risk, no studies had researched what really happened with the women taking the pill and amoxicillin together. For more than a theory makes sense, it must prove in practice that it is correct.

In recent decades this has changed, as the evidence-based medicine has gained ground in relation to what we call "theory-based medicine". Since the 1990s, the number of published works on women using antibiotics along with the pill increased exponentially, and currently we have a lot more security to issue opinions on the risks of antibiotic association with hormonal contraceptives, whether under form of pills, implants, patches or injections.

Based on extensive scientific literature, only one type of antibiotic can actually be considered responsible for reducing the efficacy of hormonal contraceptives: Rifampicin (and its derivative rifabutin). Off Rifampicin, no - yes, no - another antibiotic presented to several studies, any sign that can cut the effects of the contraceptive pill.

Therefore, from a strictly scientific point of view, there is no evidence that the vast majority of antibiotics cut the contraceptive effect of hormonal contraceptives, including the morning after pill.

Antibiotics list

This means that there is currently no scientific basis to indicate any additional care for the patients using hormonal contraceptives that must be addressed to the following antibiotics:
  • Amoxicillin (with or without clavulanate)
  • Azithromycin
  • Cephalexin
  • Cefazolin
  • Cefotaxime
  • Clarithromycin
  • Clindamycin
  • Ciprofloxacin
  • Doxycycline
  • Fosfomycin
  • Levofloxacin
  • Metronidazole
  • Minocycline
  • Moxifloxacin
  • Nitrofurantoin
  • Norfloxacin
  • Ofloxacin
  • Penicillin
  • Tetracyclines
  • Trimethoprim-sulfamethoxazole (bactrim)

The above list is not complete, it shows only the most commonly prescribed antibiotics.

It is noteworthy that women with an infection and antibiotics may have missed period. But this does not mean that the antibiotic is directly influencing the hormonal system in order to decrease the effectiveness of birth control pills.

Some women may experience vaginal bleeding escape during the use of antibiotics. This is not a pill fault indication or relevant reduction in circulating hormone levels. Studies show that these women have breakthrough bleeding have higher risk of becoming pregnant unintentionally.

Other antimicrobial drugs with action as antiviral or antifungal also show no evidence cut the effects of oral contraceptives, including acyclovir, valacyclovir, ketoconazole, fluconazole, miconazole, nystatin, etc.

The only exception to this rule are the antiretrovirals used to treat AIDS. Drugs such Nelfinavir, Nevirapine, Ritonavir, among others, relate to a reduced effectiveness of the pill. For obvious reasons, patients with HIV should not have sex without using condoms, so this question is being minimized.

Currently, none of the main gynecological associations and Midwifery world, not even the World Health Organization, indicate the use of any contraceptive protection supplement for women who use hormonal contraception and need to take an antibiotic other than rifampicin or rifambutina.

The women who need to take rifampicin or rifambutina should use an alternate non-hormonal contraceptive method throughout the duration of treatment with these antibiotics. The hormonal contraceptive may be returned first day of the menstrual cycle longer without the use of antibiotics.

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