Abstract
Plasma protein binding of ibuprofen was measured by equilibrium dialysis on 406 plasma samples collected from 15 normal volunteers following doses of 400, 800, and 1200 mg of ibuprofen as tablets (N=102, 100, 104, respectively) and 420 mg as an aqueous solution (N=100). Individual subject bound concentration at dialysis equilibrium (Cbd) vs. free concentration at dialysis equilibrium (Cfd) were well fitted via computer to the Scatchard equation with one class of binding sites. The binding capacity averaged 1231 μM (range 848–1658 μM), and the association constant averaged 1.76 × 105M−1 (range 1.15 × 105 to 2.73 × 105M−1). Distributional analysis was performed on the free fraction (fd) and bound/free ratios (Cbd/Cfd=1/fd−1) at dialysis equilibrium for each treatment. Using pooled data of all four treatments, distributional analysis was also performed on the free fractions (f) and bound/free ratios (Cb/Cf=1/f−1) corresponding to the plasma drug concentrations in blood as it was withdrawn from the subjects. The bound/free ratios were normally distributed, whereas the distributions of the free fractions were skewed towards higher values.
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This work was supported by a contract from The Upjohn Company.
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Lockwood, G.F., Albert, K.S., Szpunar, G.J. et al. Pharmacokinetics of ibuprofen in man—III: Plasma protein binding. Journal of Pharmacokinetics and Biopharmaceutics 11, 469–482 (1983). https://doi.org/10.1007/BF01062206
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DOI: https://doi.org/10.1007/BF01062206