Clarithromycin, sold under the brand name Biaxin, is an antibiotic used to treat various bacterial infections. This includes strep throat, pneumonia, skin infections, H. pylori infection, and Lyme disease, among others. Clarithromycin can be taken by mouth as a pill or liquid. Common side effects include nausea, vomiting, headaches, and diarrhea. Severe allergic reactions are rare. Liver problems have been reported. It may cause harm if taken during pregnancy. It is in the macrolide class and works by stopping the making of protein by some bacteria. Clarithromycin was developed in 1980. It is on the World Health Organization's List of Essential Medicines the most important medications needed in a basic health system. Clarithromycin is available as a generic medication. The wholesale cost in the developing world is between 0.13 and 0.79 USD per dose. In the United States it is moderately expensive at 50 to 100 USD for a course of treatment. It is made from erythromycin and is chemically known as 6-O-methylerythromycin.