Used primarily as an antimalarial medication to treat and prevent malaria, particularly in regions where the disease is resistant to other treatments. It works by interfering with the growth of parasites in the red blood cells. Additionally, it is sometimes prescribed for nocturnal leg cramps due to its muscle relaxant properties. In some cases, it is utilized in small doses as a flavoring agent in beverages, providing a bitter taste. However, its use is carefully regulated due to potential side effects such as cinchonism, which includes symptoms like tinnitus, headache, and nausea.