Effect of clonidine on plasma beta-endorphin, cortisol and growth hormone secretion in opiate-addicted subjects

The effect of clonidine on plasma beta-endorphin, cortisol and growth hormone was studied in nine opiate-addicted subjects and seven control subjects aged 15 to 37 years. Clonidine, 0.15 mg, was administered orally in the morning, 18 to 24 h after the last administration of opioid drugs. Basal morning beta-endorphin levels were lower in the addicted than in the control subjects (3.76 +/- 0.8 vs. 7.42 +/- 1.2 pmol/l). Following the clonidine, there was an increase to normal values in the addicted subjects, but in the control subjects there was no change. Basal morning levels of cortisol were higher in the addicted subjects than in the controls (21.0 +/- 3.6 micrograms/dl vs. 13.0 +/- 1.2 microgram/dl, mean +/- SE). In control subjects clonidine induced a decrease of 50% in plasma cortisol, whereas in addicted subjects the decrease was not significant. It is hypothesized that in addicted subjects there is impaired activity of endogenous opioid peptides, leading to alteration in beta-endorphin and cortisol secretion.