Short-term acetaminophen consumption enhances the exercise-induced increase in Achilles peritendinous IL-6 in humans

Through an unknown mechanism, the cyclooxygenase inhibitor and antipyretic acetaminophen (APAP) alters tendon mechanical properties in humans when consumed during exercise. Interleukin-6 (IL-6) is produced by tendon during exercise and is a potent stimulator of collagen synthesis. In nontendon tissue, IL-6 is upregulated in the presence of cyclooxygenase inhibitors and may contribute to alterations in extracellular matrix turnover, possibly due to inhibition of prostaglandin E2 (PGE2). We evaluated the effects of APAP on IL-6 and PGE2 in human Achilles peritendinous tissue after 1 h of treadmill exercise. Subjects were randomly assigned to a placebo (n = 8, 26 ± 1 yr) or APAP (n = 8, 25 ± 1 yr) group. Each subject completed a nonexercise and exercise experiment consisting of 6 h of microdialysis. Drug (APAP, 1,000 mg) or placebo was administered in a double-blind manner during both experiments. PGE2 and IL-6 were determined via enzyme immunoassay and APAP via high-performance liquid chromatography. In sub...