Effect of fenoprofen on thyroid function tests.
We observed that a few patients taking the anti-inflammatory drug fenoprofen showed increases in total and free T3 serum levels without convincing evidence of an associated thyrotoxicosis. To confirm these findings, two volunteers were given fenoprofen for two weeks. Within this time total T3 levels almost doubled and free T3 levels increased threefold. Administration of fenoprofen did not have any measurable effect on T4 or TSH estimations. Cross-reactivities of fenoprofen and 4'-hydroxyfenoprofen were studied with antisera from various total and free T3 assays. Results show that the metabolite cross-reacts with the antisera from Amerlex total and free T3 assay kits. A lesser degree of interference was observed with the Corning total and free T3 assays. 4'-hydroxyfenoprofen had no effect on an 'in house' total T3 assay. Laboratories should therefore be aware of the possibility that their assay may be subject to interference by fenoprofen or its metabolites while clinicians should be aware of this interference in order that they may avoid unnecessary and harmful treatment.
D000328:Adult; D000368:Aged; D005189:False Positive Reactions; D005260:Female; D005279:Fenoprofen / Q000494:pharmacology*; D006801:Humans; D007118:Immunoassay; D008297:Male; D008875:Middle Aged; D010666:Phenylpropionates / Q000494:pharmacology*; D011933:Reagent Kits, Diagnostic; D013972:Thyrotropin / Q000097:blood; D013973:Thyrotropin-Releasing Hormone; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood*
D010666:Phenylpropionates; D011933:Reagent Kits, Diagnostic; D014284:Triiodothyronine; D013973:Thyrotropin-Releasing Hormone; D013972:Thyrotropin; D013974:Thyroxine; D005279:Fenoprofen