Abstract
Sulfadimethoxine was administered intravenously and orally to five swine. More than 75% of the dose was excreted into urine as the acetyl metabolite with 4–6% excreted unchanged. Plasma and urine data were not consistent when a linear pharmacokinetic model was used to describe the data. Sulfadimethoxine has a high affinity for plasma protein, and the data were subsequently fitted to a nonlinear model, which included saturable protein binding. The choice of a nonlinear model was further supported by a minimum value for the Akaike information criteria. The protein binding constant obtained was 2.8× 104 M−1 and the total protein binding site concentration in plasma was 4.6×10−4 m. Both values are comparable with in vitrodata. This result suggests that the nonlinear model involving protein binding can be successfully applied to pharmacokinetic data. The apparent biological half-life of Sulfadimethoxine (free and bound) in plasma was 14 hr; however, the half-life of elimination of free drug was 1.25 hr. Following oral administration, all of the dose was absorbed with an apparent absorption half-life of 2.9 hr.
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Supported in part by FDA contract 74–178. Presented at the APhA Academy of Pharmaceutical Sciences 25th National Meeting, Hollywood, Fla, November 12–16, 1978.
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Bevill, R.F., Koritz, G.D., Rudawsky, G. et al. Disposition of sulfadimethoxine in swine: Inclusion of protein binding factors in a pharmacokinetic model. Journal of Pharmacokinetics and Biopharmaceutics 10, 539–550 (1982). https://doi.org/10.1007/BF01059036
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DOI: https://doi.org/10.1007/BF01059036