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Key value for chemical safety assessment

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Absorption and distribution

After oral application of phenazone (300 mg and 600 mg) plasma levels of 11 ug/mL and 21 ug/mL after 1 h to 3 h, respectively, and half life times ranging from 10 h to 13 h could be observed.


The predominant biotransformation step of phenazone is hydroxylation with two main metabolites 4-hydroxy-phenazone and 3 -hydroxymethyl-phenazone and subsequent glucuronidation. Conjugates (glucoronides and sulphates) of the hydroxylated intermediates will be excreted with the urine.


Excretion of phenazone after oral application is predominantly with the urine (more than 99 % in 5 days).