Clarithromycin prescribed for: Clarithromycin is effective against susceptible bacteria causing infections of the middle ear, tonsillitis, throat infections, laryngitis, bronchitis, pneumonia, and skin infections. It is also used in treating infections caused by mycobacterium avium, an organism closely related to the bacteria that causes tuberculosis. Clarithromycin has been used in combination with omeprazole, omeprazole/sodium bicarbonate (Prilosec) in treating H. Pylori bacteria that causes stomach ulcers.