Abstract
Summary
Effect of nonsteroidal antiinflammatory drugs on plasma protein-thyroxine interaction was studied by measuring muscle or resin uptake of labeled thyroxine in vitro or by measuring plasma PBI and fecal loss of thyroxine in thyroidectomized rats treated with stable and labeled thyroxine. All 9 nonsteroidal antiinflammatory drugs tested displaced thyroxine from the binding sites of plasma protein in vitro. Mefenamic acid and flufenamic acid had the strongest, oxyphenbutazone, indomethacin and phenylbutazone had the intermediate and sulpyrine, acetyl salicylate, sodium salicylate and bucolome had the least effect. Six nonsteroidal antiinflammatory drugs depressed plasma PBI and increased fecal loss of thyroxine by displacing thyroxine from the binding sites of plasma protein in vivo. The magnitude of in vivo thyroxine displacing activity correlated well with that of in vitro displacing activity.
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