Summary
The fluorometric method of Holt & Hawkins (1965) has been modified to permit determination of 50 ng indomethacin in 0.5 ml plasma, by measuring its fluorescence in a phosphate buffer at pH 11.6 instead of sodium hydroxide. The method has also been adapted to show the presence of salicylic acid and a column chromatographic method has been devised for its removal. The protein binding of indomethacin in human plasma was calculated to be about 90% from an association constant of 0.86×103 M−1 (M=molarity). The number of binding sites on albumin is about 15. The plasma levels of indomethacin in patients receiving continuous treatment with Indocid® were between 0.5 and 3 µg/ml during the 4–5 h immediately after the last dose of 25 mg. The disappearance of indomethacin from plasma appears to consist of a fast primary phase at plasma concentrations greater than 1 µg/ml (T 1/2 about 90 min.), and a slower secondary phase.
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Hvidberg, E., Lausen, H.H. & Jansen, J.A. Indomethacin: Plasma concentrations and protein binding in man. Eur J Clin Pharmacol 4, 119–124 (1972). https://doi.org/10.1007/BF00562508
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DOI: https://doi.org/10.1007/BF00562508