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Do antibiotics make birth control pills less effective?
Early data about 20 years ago seemed to indicate that when antibiotics were taken along with birth control pills, more women got pregnant than you would normally expect. Drugs like ampicillin and tetracycline were suspected to interfere with OCPs (3). However, all of the recent studies that have looked at this, have shown that antibiotics do not increase the pregnancy rate at all (4) and they point out that the old data was not reliable enough to draw conclusions about pregnancy rates on any of the antibiotics (5).
Some antibiotics have been studied and shown not to affect the metabolism of OCPs. Ciprofloxcin (Cipro ®) is one that does not seem to alter metabolism (6). Fluconazole (Diflucan ®) does not decrease estrogen levels in pill users; if anything, it raises estrogen levels (7).
