Diclofenac increases beta-endorphin plasma concentrations.

Plasma and ventricular cerebro-spinal fluid (CSF) Beta-endorphin concentrations were evaluated after chromatographic separation in patients carrying a ventricular shunt before and after the administration of diclofenac or placebo. In the same subjects the ventricular CSF concentrations of the serotonin and the catecholamine metabolites 5-hydroxyindole-acetic acid (5-HIAA), homovanillic acid (HVA) and MOPEG were also evaluated. Plasma, but not ventricular, Beta-endorphin concentrations increased significantly after diclofenac, while placebo was ineffective. No significant changes in ventricular 5-HIAA, HVA or MOPEG levels were observed. These data suggest a role for Beta-endorphin in the analgesic effect of diclofenac.