List of products in the National Drug Code with proprietary name . This medication is used to treat toenail infection caused by fungus. It works by stopping the growth of certain types of fungus. Efinaconazole belongs to a class of drugs known as azole antifungals. This medication treats only fungal infections. It will not work for other types of infection, such as those caused by bacteria. Unnecessary use or overuse of any drug used to treat infection can lead to its decreased effectiveness.