Effect of misoprostol on concentrations of prostaglandins in synovial fluid

The effect of misoprostol, a synthetic analogue of prostaglandin E, on prostaglandin concentrations in synovial fluids was investigated in a randomised placebo controlled, double blind study. The synovial fluid concentrations of prostaglandin E1, 6-keto-prostaglandin F1 alpha, and thromboxane B2 were measured at the beginning and end of a 24 hour period in 25 patients with effusions of the knee joint. During this period the patients were treated with diclofenac (50 mg every eight hours) and either misoprostol (400 micrograms) or placebo every 12 hours. The concentrations of prostaglandin E and 6-keto-prostaglandin F1 alpha were not significantly altered during treatment. There was an unexpected significant reduction in thromboxane B2 concentrations in the group treated with misoprostol (within group analysis). Although the mean concentration with misoprostol was about half the mean concentration with placebo, this difference was not statistically significant in the between group analysis. These results indicate that misoprostol is unlikely to exert a proinflammatory effect or to interfere with the prostaglandin mediated effects of non-steroidal anti-inflammatory drugs. The significant decrease in thromboxane B2 concentrations in the misoprostol treated group suggests that misoprostol may exert an anti-inflammatory effect.