The metabolism of [carboxyl-14C]aspirin in man.

1. [carboxyl-14C]Aspirin has been orally administered to four male volunteers and the urinary metabolites examined by paper chromatography, t.l.c., h.p.l.c. and mass spectrometry. 2. 14C Radioactivity was eliminated rapidly in the urine, 94 to 98% of the dose in the first 24 h and approx. 1% in 24-48 h. 3. The major urinary metabolite was salicyluric acid (56-68% dose). In addition, free salicylic and gentisic acids were also detected as were both the acyl and phenolic glucuronides of salicylate. 4. A phenolic glucuronide of salicyluric acid has also been identified. The importance of this metabolite in relation to analytical methods for salicylphenolic glucuronide determination is discussed. 5. The presence of other di- and tri-hydroxybenzoic acids or gentisuric acid could not be demonstrated.