Antibiotics and Birth Control Pills

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Antibiotics and Birth Control Pills

When taking Birth Control Pills and antibiotics, it is generally not necessary to use any form of back-up contraception.

Years ago, researchers discovered that women on BCPs who were taking antibiotics had small but measurable reductions in their blood hormone levels. It was felt that the use of antibiotics may have lead to altered intestinal flora and ultimately to changed levels of hormone in the patient's blood stream. This observation led some authorities to suggest the use of back-up contraception, believing that the changed levels of hormone might diminish the effectiveness of the BCP. This was their theory, based on the reduced blood levels of hormone and not on any studies of human population pregnancy rates.

In controlled studies, this theory has not been proven, and in the case of tetracycline and chlortetracycline, no increased risk of pregnancy was found.

If taking antibiotics has any effect at all on pregnancy rates, the effect must be very small and is not likely to have much clinical relevance in an operational setting.

For these reasons, women taking BCPs who need antibiotics should not avoid the combination for fear of pregnancy.

This information is provided by The Brookside Associates. The Brookside Associates, LLC. is a private organization, not affiliated with any governmental agency. The opinions presented here are those of the author and do not necessarily represent the opinions of the Brookside Associates or the Department of Defense. The presence of any advertising on these pages does not constitute an endorsement of that product or service by either the US Department of Defense or the Brookside Associates. All material presented here is unclassified.

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