The anti-inflammatory effects of Ph CL28A, a potentiator of prostacyclin output and inhibitor of leukotriene (LT) synthesis, were assessed in two models of acute inflammation. In paw oedema induced by carrageenan in rats, Ph CL28A (10-100 mg/kg), given i.p. at the same time as the carrageenan, inhibited oedema for up to 4 h. When indomethacin or Ph CL28A was given locally into the paw with carrageenan, indomethacin inhibited oedema formation but Ph CL28A potentiated the oedema for up to 4 h. As Ph CL28A does not inhibit cyclo-oxygenase, its anti-inflammatory effects in this model may reflect its ability to increase prostacyclin output. In pleurisy induced by carrageenan in rats, there were increases in leukocytes, LTB4, thromboxane B2 (TxB2) and 6-oxo-prostaglandin F1 alpha (6-oxo-PGF1 alpha) in the pleural fluid over 3 h. In this model, Ph CL28A (30 mg/kg) given i.p. decreased leukocyte numbers and LTB4 but did not affect TxB2 or 6-oxo-PGF1 alpha. Indomethacin decreased both prostanoids but did not affect leukocyte accumulation. The beneficial effects of Ph CL28A in two different models of acute inflammation suggests that it may have potential as an anti-inflammatory agent.231237-42