Comparative Tissue Absorption of Oral ¹⁴C‐Aspirin and Topical Triethanolamine ¹⁴C‐Salicylate in Human and Canine Knee Joints

Abstract: The local, articular, and systemic absorption of oral and topical salicylates was studied in dogs and humans using radioisotope techniques. Topical triethanolamine ¹⁴C‐salicylate was found capable of percutaneous absorption into the knee joint and surrounding tissues. In dogs, topical salicylate application resulted in higher salicylate concentrations than oral aspirin in a number of tissues, despite lower blood levels. In patients with rheumatoid arthritis, intraarticular ¹⁴C‐salicylate levels after triethanolamine ¹⁴C‐salicylate cream were 60 per cent of those obtained with oral aspirin. Four of six patients reported equal improvement in local discomfort after oral and topical salicylates. A potential role for topical salicylate cream in the treatment of localized rheumatic disorders is suggested. 1982 American College of Clinical Pharmacology