Metamizole sodium or dipyrone is a powerful analgesic and antipyretic. It is marketed under various trade names, including Algozone, Algocalmin, Analgin, Dipirona, Novalgin, Neo-Melubrina and Optalgin. Metamizole was first synthesized by the German company Hoechst AG (now part of Sanofi) in 1920, and its mass production started in 1922. It remained available worldwide until the 1970s, when it was discovered that the drug carries a small risk of causing agranulocytosis – a potentially fatal condition. Controversy remains regarding the level of risk. Several national medical authorities have banned metamizole either totally or have restricted it to be available only on prescription, while others have maintained its availability over the counter.