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.

Determination of an oral aflatoxin dose that acutely impairs hepatic function in domestic pigeons (Columba livia).

Aflatoxin B1 is a common hepatotoxin in birds. The goal of this study was to establish an acute model for hepatotoxicosis and decreased hepatic function in the white Carneaux pigeon (Columba livia) via oral administration of this mycotoxin. Aflatoxin B1 was orally administered at a dose of 3 mg/kg dissolved in dimethyl sulfoxide to 3 groups of pigeons every 24 hours for 2, 4, and 6 consecutive days, respectively. Diagnostic modalities used to evaluate hepatic damage and impaired hepatic function pre- and postaflatoxin administration included liver enzyme activity, bile acid levels, scintigraphy, and histopathologic evaluation of liver biopsy specimens. Deaths occurred in all groups, increasing with the number of consecutive days the aflatoxin B1 was dosed. Significant histopathologic lesions were seen on evaluation of hepatic tissue from each group after accumulated aflatoxin exposure (P < .05); therefore, an oral aflatoxin B1 dose of 3 mg/kg given for 2 consecutive days was selected for the purpose of inducing acute hepatic damage while minimizing mortality. However, although increased liver enzyme activity indicated hepatocellular damage at this dosage, bile acids testing and hepatobiliary scintigraphy did not show significantly decreased hepatic function.

Effects of dietary milk thistle on blood parameters, liver pathology, and hepatobiliary scintigraphy in white carneaux pigeons (Columba livia) challenged with B1 aflatoxin.

Milk thistle (Silybum marianum) has been used in humans for the treatment of liver disease because of its antioxidant properties and its ability to stabilize cell membranes and regulate cell permeability. To investigate possible hepatoprotective effects in birds, standardized extracts (80%) of silymarin from milk thistle were tested in white Carneaux pigeons (Columba livia). Pigeons were separated into 3 groups and fed diets formulated to provide milk thistle at a level of 0, 10, or 100 mg/kg body weight per day. After acclimation, the birds were challenged with B1 aflatoxin (3 mg/kg body weight for 2 consecutive days) by oral gavage. Liver function then was assessed by hematologic testing and plasma biochemical analysis, liver histopathology, and hepatobiliary scintigraphy. Results of histopathology and hepatobiliary scintigraphy showed no protective effects from milk-thistle administration. Aflatoxin challenge resulted in hepatic inflammation and necrosis, biliary-duct hyperplasia, and lymphocyte infiltration. All hepatobiliary scintigraphy elements increased significantly after aflatoxin challenge. Bile acid levels and plasma enzyme concentrations of aspartate aminotransferase, lactate dehydrogenase, alanine aminotransferase, and creatine phosphokinase all increased after aflatoxin exposure and were mostly unchanged with consumption of milk thistle. Only birds fed 10 mg/kg body weight milk thistle showed significant reductions in lactate dehydrogenase, alanine aminotransferase, and creatine phosphokinase concentrations after aflatoxin exposure. Our results show that consumption of milk thistle is not associated with hepatoprotective effects against acute B1 aflatoxin exposure in pigeons.

Pharmacokinetics and egg residues after oral administration of a single dose of meloxicam in domestic chickens (Gallus domesticus).

OBJECTIVE To determine the pharmacokinetics of meloxicam in domestic hens and duration and quantity of drug residues in their eggs following PO administration of a single dose (1 mg of meloxicam/kg). ANIMALS 8 healthy adult White Leghorn 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, egg whites (albumen), and egg yolks were analyzed by high-performance liquid chromatography. RESULTS The half-life, maximum concentration, and time to maximum concentration of meloxicam in plasma samples were 2.8 hours, 7.21 µg/mL, and 2 hours, respectively. Following meloxicam administration, the drug was not detected after 4 days in egg whites and after 8 days in egg yolks. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that meloxicam administered at a dose of 1 mg/kg PO in chickens appears to maintain plasma concentrations equivalent to those reported to be therapeutic for humans for 12 hours. The egg residue data may be used to aid establishment of appropriate drug withdrawal time recommendations.