Breed differences in the pharmacokinetics of orally administered meloxicam in domestic chickens (Gallus domesticus).

OBJECTIVE: To determine the pharmacokinetics of meloxicam in Wyandotte hens and duration and quantity of drug residues in their eggs following PO administration of a single dose (1 mg of meloxicam/kg [0.45 mg of meloxicam/lb]) and compare results with those previously published for White Leghorn hens. ANIMALS: 8 healthy adult Wyandotte hens. PROCEDURES: Hens were administered 1 mg of meloxicam/kg, PO, once. A blood sample was collected immediately before and at intervals up to 48 hours after drug administration. The hens' eggs were collected for 3 weeks after drug administration. Samples of the hens' plasma and egg whites (albumen) and yolks were analyzed with high-performance liquid chromatography. RESULTS: Mean ± SD terminal half-life, maximum concentration, and time to maximum concentration were 5.53 ± 1.37 hours, 6.25 ± 1.53 µg/mL, and 3.25 ± 2.12 hours, respectively. Mean ± SD number of days meloxicam was detected in egg whites and yolks after drug administration was 4.25 ± 2 days and 9.0 ± 1.5 days, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Compared with White Leghorn hens, meloxicam in Wyandotte hens had a longer terminal half-life, greater area under the plasma concentration-versus-time curve from time 0 to infinity, a smaller elimination rate constant, and a longer mean residence time-versus-time curve from time 0 to infinity, and drug persisted longer in their egg yolks. Therefore, the oral dosing interval of meloxicam may be greater for Wyandotte hens. Results may aid veterinarians on appropriate dosing of meloxicam to Wyandotte hens and inform regulatory agencies on appropriate withdrawal times.

Pharmacokinetics and Drug Residue in Eggs After Multiple-Day Oral Dosing of Amoxicillin-Clavulanic Acid in Domestic Chickens.

This study examined the pharmacokinetics of orally administered amoxicillin and clavulanic acid tablets (Clavamox, 125 mg/kg PO q12h for 9 doses) in domestic hens and examined both amoxicillin and clavulanic acid concentrations in eggs. Therapeutic plasma concentrations (0.5 µg/mL) of amoxicillin were not reached at any time point, and no amoxicillin was detected in plasma after 2 hours. Pharmacokinetic parameters could not be calculated. The clavulanic acid half-life was 1.1 hours and it was detected up to 8 hours after dosing. No amoxicillin was detected in eggs 4 days postdosing, nor was clavulanic acid detected in any eggs during the same time period. On the basis of these results, orally dosing hens with amoxicillin and clavulanic acid tablets at 125 mg/kg PO q12h does not reach therapeutic plasma concentrations. Additional studies are needed to examine different doses and formulations of medication to determine better dosing and withdrawal recommendations for domestic chickens.