The effect of non-steroidal anti-inflammatory therapy on plasma neuropeptide concentrations in patients with osteoarthritis.

Plasma levels of the endogenous opioid peptides beta-endorphin and [Met]enkephalin were estimated in 10 osteoarthritic patients during treatment with a sustained-release indomethacin preparation (Osmosin). Significant diurnal variation of beta-endorphin levels was evident both on and off treatment (p less than 0.05, respectively), but the therapy was nevertheless accompanied by decreased morning levels of this peptide; no such changes were recorded for [Met)enkephalin. Whilst the treatment was associated with a reduction of pain, particularly in the evening (p less than 0.02), no correlation was evident between pain and beta-endorphin levels, nor between the patients' perception of pain relief and changes in beta-endorphin levels. The results suggest either that prostaglandins may be involved in the synthesis/release of beta-endorphin, or that the alleviation of stress may in turn reduce the need for continued beta-endorphin production in these patients.