REVIEW Dipyron hydrate (metamizole), is an non-opioid analgesic (pain reliever) and antipyretic (fever reducer) and is one of the most frequently used painkillers in the world. Metamizole sodium is marketed under various trade names, including Algozone, Algocalmin, Algopyrin, 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 linked with a small risk of causing agranulocytosis, a potentially fatal condition. Those results have been disputed in meta-analyses conducted in the 2000s. Regardless, several national medical authorities have withdrawn metamizole from the market altogether or have restricted it to be available only with a prescription, although it remains available over the counter in many countries.
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