Last week I had three patients tell me they became pregnant while taking an antibiotic when using the birth control pill. I was impressed they felt like having sex while under the weather! When asked if they knew that some antibiotics lower the effectiveness of the pill, all three responded the exact same, “Well I know that now!”
While there are no long-term or large focus studies on the subject, it is true that some medications get in the way of your birth control pill doing its job to protect you from pregnancy. Only one, rifampin, has been absolutely studied. However, there is a list of others to consider:
• Penicillin
• Amoxicillin
• Sulfonamide
• Ampicillin
• Cotrimoxazole
• Tetracycline
• Griseofulvin
• Minocycline
• Phenobarbitol
• Metronidazole
• Nitrofurantoin
The thought process behind this involves your liver. Antibiotics speed up an enzyme that rapidly breaks down the pill, moving it out of your system much faster than normal.
Bottom line is to use a back-up method (such as a condom) when you have to take antibiotics to be safe. Also, if you are taking the very low dose pill, you are at more risk because your levels are already lower than other traditional pill amounts.