Clarithromycin is used to treat certain bacterial infections, such as pneumonia (a lung infection), bronchitis (infection of the tubes leading to the lungs), and infections of the ears, sinuses, skin, and throat.Clarithromycin is as potent and effective as any other antibiotic when taken in a dosage of 500mg. With its very mild side effects, Clarithromycin is available both as a liquid and a pill to fight an array of bacterial infections.