Faropenem 300 mg ER (extended release) works by releasing the medicine slowly over time, whereas the regular 300 mg tablet is absorbed more quickly after you take it. Because they act differently in the body, they are not usually interchangeable. Switching to the extended-release version without medical advice could make the treatment less effective. The right form depends on the type of infection and how often the medicine needs to be taken. It is best to follow your doctor’s prescription as given. If you cannot find the prescribed version, check with your doctor before making any change, as they can suggest the correct alternative and dosing for your condition.