Development of a physiologic-based pharmacokinetic model for estimating sulfamethazine concentrations in swine and application to prediction of violative residues in edible tissues.
OBJECTIVE
To develop a flow-limited, physiologic-based pharmacokinetic model for use in estimating concentrations of sulfamethazine after IV administration to swine.


METHODS
4 published studies provided physiologic values for organ weights, blood flows, clearance, and tissue-to-blood partition coefficients, and 3 published studies provided data on plasma and other tissue compartments for model validation.


METHODS
For the parent compound, the model included compartments for blood, adipose, muscle, liver, and kidney tissue with an extra compartment representing the remaining carcass. Compartments for the N-acetyl metabolite included the liver and the remaining body. The model was created and optimized by use of computer software. Sensitivity analysis was completed to evaluate the importance of each constant on the whole model. The model was validated and used to estimate a withhold interval after an IV injection at a dose of 50 mg/kg. The withhold interval was compared to the interval estimated by the Food Animal Residue Avoidance Databank (FARAD).


RESULTS
Specific tissue correlations for plasma, adipose, muscle, kidney, and liver tissue compartments were 0.93, 0.86, 0.99, 0.94, and 0.98, respectively. The model typically overpredicted concentrations at early time points but had excellent accuracy at later time points. The withhold interval estimated by use of the model was 120 hours, compared with 100 hours estimated by FARAD.


CONCLUSIONS
Use of this model enabled accurate prediction of sulfamethazine pharmacokinetics in swine and has applications for food safety and prediction of drug residues in edible tissues.
Buur
Jennifer L
JL
Food Animal Residue Avoidance Databank, Center for Chemical Toxicology Research and Pharmacokinetics, Department of Population Health and Pathobiology, College of Veterinary Medicine, North Carolina State University, Raleigh 27606, USA.
Baynes
Ronald E
RE
Craigmill
Arthur L
AL
Riviere
Jim E
JE
D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D007275:Injections, Intravenous / Q000662:veterinary; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008954:Models, Biological; D018482:Muscle, Skeletal / Q000378:metabolism; D013418:Sulfamethazine / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D013552:Swine / Q000378:metabolism*; D014018:Tissue Distribution
D013418:Sulfamethazine