Hepatic to 2-amino-3-acetylamino-6-(para-fluorobenzylamino) pyridine (which has 20-30% the analgesic potential of its parent compound), para-fluorohippuric acid[3] and a mercapturic acid metabolite, presumably formed from a glutathione adduct[4]
Flupirtine is an aminopyridine that functions as a centrally acting non-opioidanalgesic that was originally used as an analgesic for acute and chronic pain[5] but in 2013 due to issues with liver toxicity, the European Medicines Agency restricted its use to acute pain, for no more than two weeks, and only for people who cannot use other painkillers.[6] In March 2018, marketing authorisations for flupirtine were withdrawn following a European Medicines Agency recommendation based on the finding that the restrictions introduced in 2013 had not been sufficiently followed in clinical practice, and cases of serious liver injury still occurred including liver failure.[7]
^Narang PK, Tourville JF, Chatterji DC, Gallelli JF (January 1984). "Quantitation of flupirtine and its active acetylated metabolite by reversed-phase high-performance liquid chromatography using fluorometric detection". Journal of Chromatography. 305 (1): 135–143. doi:10.1016/S0378-4347(00)83321-6. PMID6707137.
^Methling K, Reszka P, Lalk M, Vrana O, Scheuch E, Siegmund W, et al. (March 2009). "Investigation of the in vitro metabolism of the analgesic flupirtine". Drug Metabolism and Disposition. 37 (3): 479–493. doi:10.1124/dmd.108.024364. PMID19074524. S2CID5661841.