DEVELOPMENT OF TOLERANCE TO ANTIINFLAMMATORY EFFECT OF MORPHINE

Opioid drugs, typified by morphine, are primarily used for their pain relieving properties, however, they produce a host of other effects due to the wide distribution of opioids and their receptors in both the brain and the periphery. The capacity of morphine in attenuation of inflammation and inflammatory pain has already been demonstrated. In addition, there has been evidence showing the systemic efficiency of morphine against some inflammatory diseases and reversal of such effects by naloxon.1 In the present study, after confirming the antiinflammatory effect of morphine against carrageenan-induced hind paw edema in mice (data not shown), we tried to assess the probable development of tolerance, a somehow troublesome phenomenon which extends to most effects of morphine, to its antiinflammatory effect in chronic administration.