Reduction of prostaglandin E2 concentrations in synovial fluid of patients suffering from rheumatoid arthritis following tiaprofenic acid or indomethacin treatment.

Prostaglandin E2 (PGE2) is a potent stimulator of inflammation, and the inhibition of its synthesis is one possible mechanism of action of non-steroidal anti-inflammatory drugs (NSAIDs). We have investigated patients suffering from rheumatoid arthritis to determine how synovial fluid levels of PGE2 are affected by tiaprofenic acid or indomethacin medication. Ten patients suffering from rheumatoid arthritis were studied, with 5 patients receiving tiaprofenic acid and 5 indomethacin for a 1-week period. Synovial fluid and serum samples were collected over an 8-hour period on days 1 and 8; these were then assayed for PGE2 and active drug concentrations. The concentration of PGE2 in the synovial fluid fell consistently as the concentration of each drug rose, and low levels of PGE2 persisted on continuation of the medication. Tiaprofenic acid appeared to cause a faster onset of inhibition of PGE2 synthesis than indomethacin.