Metamizole is a pyrazole with a methyl(sulfomethyl)amino group at C-4, and its sodium salt, metamizole sodium, was a potent analgesic and antipyretic used widely until the 1970s. It was withdrawn from many markets due to the risk of agranulocytosis. It functions as an antipyretic, antirheumatic drug, non-narcotic analgesic, peripheral nervous system drug, prodrug, COX-3 inhibitor, and anti-inflammatory agent. It belongs to pyrazoles and amino sulfonic acids, and is functionally related to antipyrine. It is the conjugate acid of metamizole(1-).
