Intoxication with pyrazolones

1 About 50 severe or fatal (mostly accidental) cases of intoxication in children by pyrazolones have been reported in the German literature of the past 59 years. 2 Characteristic symptoms are impaired consciousness progressing to coma and convulsions. In addition, sudden apnoea and cardiac arrest may occur. Hepatic lesions may develop after a latent period of 12-24 hours. 3 Haemoperfusion seems to be the only therapeutic measure which is able to reduce the total body load of all pyrazolones to a toxicologically relevant extent. Actual clinico-toxicological data from poisoned patients are not available as yet; however, distribution volumes, plasma half-lives and endogenous plasma clearances as well as removal kinetics in vitro of aminophenazone (aminopyrine), propyphenazone, metamizole (dipyrone), phenylbutazone and oxyphenbutazone as point to the efficacy of haemoperfusion with amberlite XAD-4 resin.