The idea has long been that antibiotics reduce the effect of the birth control pill, which has led many women to be alerted by health professionals, advising them to use condoms during treatment.
However, recent studies show that most antibiotics do not interfere with the effect of these hormones, as long as they are taken correctly, every day and at the same time.
- Recent studies show that rifampicin and rifabutin are the only antibiotics that interfere with contraceptive action.
These antibiotics are generally used to fight tuberculosis, leprosy and meningitis and as enzyme inducers increase the rate of metabolism of certain contraceptives, thus reducing the amount of these hormones in the bloodstream, committing their therapeutic effect.
While these are the only antibiotics with proven pharmacological interaction, there are others that can alter intestinal flora and cause diarrhea, and there is also a risk of reducing contraceptive absorption and not benefiting from its effect; however, they only reduce the effect of the medicine if diarrhea occurs within 4 hours of taking the contraceptive.
In addition, although this is inconclusive and although there are no studies to prove it, it is also thought that tetracycline and ampicillin can interfere with the contraceptive, reducing its effect.
If you are being treated with rifampicin or rifabutin, to avoid an unwanted pregnancy, an additional method of contraception, such as a condom, should be used during the period during which the woman is on treatment and up to 7 days after stopping treatment.
In addition, if there are episodes of diarrhea during treatment, condoms should also be used, provided diarrhea stops, up to 7 days later.
If you have unprotected sex in any of these situations, it may be necessary to take the morning-after pill. Find out how to take this medicine.