Phenylhydrazine

Endpoint summary

Additional information

Absorption 

Evidence from toxicokinetic and toxicity studies and from human experience indicates that phenylhydrazine is well absorbed by the inhalation, oral, and dermal routes in animals and humans.  

 

Distribution 

Once absorbed, phenylhydrazine appears to be rapidly taken up by red blood cells, where it binds readily to haemoglobin. There is little information available on tissue distribution.  

 

Metabolism 

Following absorption, phenylhydrazine distributes within the organism. Notably, the substance reacts with carbonyl groups, –C=O, common among biological molecules. It is therefore expected that direct binding to biological molecules would occur. Evidence from a number of studies in vitro and in vivo suggests that phenylhydrazine interacts with haemoglobin and cytochrome P-450 in an oxidation reaction (e.g., Itano et al., 1975; Valenzuela et al., 1977, 1981; Goldberg et al., 1979; Jain & Hochstein, 1979; Jonen et al., 1982; Hill, 1985; Marks, 1985; Di Cola et al., 1988, 1989; Maples et al., 1988). The main phase I reactions are hydroxylation of the aromatic ring to p-hydroxyphenylhydrazine (McIsaac et al., 1958). Following phase I metabolism phase II conjugation reactions with glucuronic acid, and production of phenylhydrazones, by reaction with natural keto acids are likely to increase excretion via urine (low molecular species) and faeces (high molecular weight species)  

 

Excretion

Excretion following a single dose application is primarily via the urine (McIsaac et al., 1958). A significant proportion of a single dose was excreted relatively slowly; 50% of the of phenylhydrazine was excreted within 4 days.