Residue depletion of melamine and cyanuric acid in catfish and rainbow trout following oral administration

Reimschuessel, R., Evans, E., Andersen, W. C., Turnipseed, S. B., Karbiwnyk, C. M., Mayer, T. D., Nochetto, C., Rummel, N. G., Gieseker, C. M. Residue depletion of melamine and cyanuric acid in catfish and rainbow trout following oral administration. J. vet. Pharmacol. Therap.33, 172–182. The intentional addition of triazines such as melamine to animal feeds and the lack of information about residue accumulation in food animals caused global concerns for food safety during 2007 and 2008. We report the results of a good laboratory practices (GLP) study to determine melamine and cyanuric acid residues in catfish and trout filets harvested at 1, 3, 7, 14, 28, and 42 days after a single oral dose of 20 mg/kg body weight of melamine, cyanuric acid, or melamine and cyanuric acid together. Peak melamine concentrations were 12.73 mg/kg (ppm) in catfish (mean = 9.98), 12.26 mg/kg in trout (mean = 7.89) on day 1. Within 7 days (catfish) or 14 days (trout) residues were <2.5 mg/kg, a level in foods accepted by many risk assessors worldwide to be unlikely to pose health risks to consumers. Peak cyanuric acid residues also occurred on day 1, 0.68 mg/kg in catfish (mean = 0.46), 2.59 mg/kg in trout (mean = 0.86). Cyanuric acid muscle residues were <2.5 mg/kg by day 3. The half-lives for melamine and cyanuric acid ranged between 1 and 4 days. Renal crystals formed in fish given both melamine and cyanuric acid, persisting for weeks after the single dose.