One or two weeks should be a minimal risk. I am in Mexico and the doctors opinions here differ anywhere from 7 days to 21 days. The amoxicillin is very effective against many forms of bacteria, but is limited by bacteria resistance patterns. The drug is usually used three times a day and not twice. Five hundred milligrams would be an adequate dose, as would 875 mg twice a day.
Sinus infections are notorious for taking long amounts of time to cure.
Why then would that be prescribed over the Amoxil. By the prescribed over the Amoxil. By the way this was prescribed for otitis media and slight bronchitis. Augmentin is a combination of Amoxicillin and Clavulanate potassium. Clavulanate potassium is technically the potassium salt of clavuligerus.