Have you heard the theory that antibiotic use can lessen the effectiveness of your birth control pill? Though there is some truth to this theory, it’s fortunately NOT true for most commonly prescribed antibiotics.
Pharmacologic studies evaluating hormonal levels during antibiotic use have shown decreased hormonal levels (leading in theory to potential decreased effectiveness) with only one type of antibiotic, Rifampin (an anti-tuberculosis medication) whose use is fairly uncommon. Women taking this particular antibiotic should not rely on their hormonal birth control (OCP, DepoProvera, or implant) solely for contraception during its use. Use of a non-hormonal form of back-up birth control is recommended in these women.
Other antibiotics have NOT been proven to affect the pharmacologic levels of hormonal contraception. Some of the more commonly used antibiotics, metronidazole, ampicillin, tetracycline, doxycycline, ciprofloxacin, or diflucan have not shown to decrease oral contraceptive levels in pharmacologic studies.
For women taking antibiotics (other than Rifampin) with birth control pills, back-up contraception is therefore, not required.
If you are sick, requiring antibiotic use or not, considerations for decreased effectiveness of your birth control pill may be due to missed pills, or due to vomiting, in which case back-up birth control would be recommended.