Amoxicillin is a penicillin antibiotic that fights bacteria. It is used to treat many types of infections such as tonsillitis, bronchitis, pneumonia, and others. Amoxicillin: learn about side effects, dosage, special precautions, and more on MedlinePlus Find patient medical information for Amoxicillin (Amoxil and others) on WebMD including its uses, side effects and safety, interactions, pictures, warnings, and user ratings Learn what amoxicillin 500mg treats, how to take it safely, and what side effects to watch for, including tips on allergies and finishing your course. Amoxil (amoxicillin) is a penicillin antibiotic used to treat many different types of infections caused by bacteria. Includes Amoxil side effects, interactions, and indications. For most adults, the standard amoxicillin dose is 500 mg every 8 hours or 875 mg every 12 hours. Most courses run 7 to 10 days, though the exact length depends on the type of infection. Amoxicillin is used to treat bacterial infections in many different parts of the body (ear, lungs, nose, sinus, skin, urinary tract). It is also used with other medicines (eg, clarithromycin, lansoprazole) to treat H. pylori infection and duodenal ulcers.