Amoxicillin, a penicillin antibiotic that fights bacterial infection, can make birth control pills less effective, according to Drugs.com. If you are concerned about preventing pregnancy, talk to your doctor about alternative, reliable forms of birth control to use during a course of antibiotics.
Drugs.com explains that amoxicillin is prescribed for a wide variety of bacterial infections, including sinus infections, ear infections, pneumonia and bladder infections. WebMD says that amoxicillin works by stopping the growth of the bacteria causing an infection. Before using amoxicillin, tell your doctor if you have ever had an allergic reaction to a penicillin or cephalosporin antibiotic. In order to prevent antibiotic resistance or a return of the infection, take all of the medication exactly as prescribed, even if you begin to feel better before you have finished all the medication.