Can sulfa antibiotics ie. bactrim (sulfamethoxazole and trimethoprim) affect oral birth control?

Theoretical: This is talked about much more than it really happens. But to be on the safe side you can use condoms as a back up while you are on the antibiotics.

Yes: Any antibiotic can cause absorption issues with ocp's and render them ineffective. One should always ask about medications use with ocp's and the medication's effect on the ocp. If in doubt, use a back up method (comdon, foam, film etc) and talk to your pcp/gyn about it. Don't risk it! the price may be too high to pay!

Yes: Antibiotics that have been shown to interact with birth control pills include Rifampin (brand name rifadin), and to a lesser extent, penicillin (veetids), Amoxicillin (amoxil), Ampicillin (omnipen), sulfamethoxazole/trimethoprim (septra (sulfamethoxazole and trimethoprim) or bactrim), tetracycline (sumycin), Minocycline (minocin), Metronidazole (flagyl), and Nitrofurantoin (macrobid or macrodantinhttp://www.Drugstore.Com/ask/do-anti.