4-Formylaminoantipyrine is an excreted metabolite of aminophenazone. Aminophenazone is a pyrazolone with analgesic, anti-inflammatory, and antipyretic effects in vivo[1].
[1]. M Levy, et al. Impairment of the metabolism of dipyrone in asymptomatic carriers of the hepatitis B virus. Clin Pharmacol Ther
[2]. A Noda, et al.Formation of 4-formylaminoantipyrine as a new metabolite of aminopyrine. II. Enzymatic demethylation and oxidation of aminopyrine and 4-monomethylaminoantipyrine. Chem Pharm Bull (Tokyo).1976 Dec;24(12):3229-31.
[3]. David do C Malvar, et al. Dipyrone metabolite 4-MAA induces hypothermia and inhibits PGE2 -dependent and -independent fever while 4-AA only blocks PGE2 -dependent fever. Br J Pharmacol. 2014 Aug;171(15):3666-79.