Phenazone ( INN and BAN ; also known as phenazon , antipyrine ( USAN ), or analgesine ) is an analgesic , a nonsteroidal anti-inflammatory drug (NSAID) and an antipyretic . It was first synthesized by Ludwig Knorr in 1887.   :26–27 Phenazone is synthesized  by condensation of phenylhydrazine and ethyl acetoacetate under basic conditions and methylation of the resulting intermediate compound 1-phenyl-3-methylpyrazolone  with dimethyl sulfate or methyl iodide . It crystallizes in needles which melt at 156 °C. Potassium permanganate oxidizes it to pyridazine tetracarboxylic acid. Phenazone has an elimination half life of about 12 hours.  Indication: Used to relieve pain and fever. Antipyrine is often used in testing the effects of other drugs or diseases on drug-metabolizing enzymes in the liver.