Pharmacokinetic study of clazuril (Appertex®) in eggs and plasma from laying hens after single or multiple treatments, using a new HPLC method for detection

Abstract

1. Anticoccidials are widely used as food additives to prevent and treat coccidiosis. They are licensed for use in a prescribed concentration and during a specific time interval with broilers and pullets, but not for laying hens. 2. This study was set up to develop a new high pressure liquid chromatography (HPLC) method to detect clazuril (CZ: (±)-2-chloro - (4-chlorophenyl)-4- (4,5-dihydro-3,5-dioxo-1,2,4-triazin-2(3H)-yl)-benzeneacetonitrile) in egg yolk and albumen and in plasma; to investigate both the presence of residues of CZ in eggs and its pharmacokinetic behaviour in laying hens. 3. A single oral dose (3mg/kg BW) and multiple oral doses (3mg/kg BW for 5d) were investigated. The analytical method gave very good recovery (64 to 74%) in the three different matrices (yolk, albumen and plasma); precision and accuracy were within 11%. 4. After a single dose no residue was detected in eggs collected for up to 10d, while following multiple dose treatment, CZ residues were detected until 10d after the end of treatment. The concentration of the drug was higher in yolk than in albumen with a maximum ratio of 10:1. 5. Pharmacokinetics of CZ in laying hens after a single dose showed a detectable concentration of the drug up to 24h. It reached a steady state after the third administration in multiple dosing. 6. Although further studies are necessary, these results indicate that a single oral dose of CZ could be used as an anticoccidial for laying hens due to the lack of residues in eggs.