Novel approach to control sulfamethazine misuse in food-producing animals by hair analysis.

The presence of sulfamethazine residues in pig and calf hair was compared with the residual levels encountered in the corresponding edible tissues (liver and muscle) as a consequence of drug administration. Sulfamethazine up to 84.7 mg kg-1 was found in calf hair samples after a pharmacological treatment, with a significant effect of hair pigmentation. High concentrations of the parent drug were detected in calf hair for 4 weeks after administration, when sulfamethazine residues were no longer detectable in the corresponding edible tissues. In a similar way, pig hair also accumulated sulfamethazine residues up to 40.5 mg kg-1, which was more than the amount detected in the corresponding muscle and liver samples at slaughter. Hair analysis seems a suitable tool to improve the efficacy of regulatory controls, and thus the safety of the food chain and to discourage the improper use of sulfamethazine in animal farming.