EFFECTS OF TRAMADOL ON IMMUNE-RESPONSES AND NOCICEPTIVE THRESHOLDS INMICE

Tramadol is a centrally acting analgesic drug with a dual mechanism of action: binding to Ir-opioid receptors and potentiation of the monoam inergic systems. In this study, we evaluated the effects of the acute and chronic administration of tramadol on nociceptive thresholds (by t he hot-plate lest) and on immune responses (by measuring Concanavalin A-induced splenocyte proliferation, IL-2 production and natural killer activity) in the mouse. After acute subcutaneous administration, tram adol induced antinociception starting from a dose of 20 mg/kg, whereas it significantly enhanced natural killer activity and IL-2 production at doses as low as 1 mg/kg and splenocyte proliferation starting from a dose of 10 mg/kg. After the chronic administration, the antinocicep tive effect of the drug was still present, whereas the immune modifica tions disappeared. Thus, the pharmacological profile of tramadol is to tally different from that of other drugs which bind mu-opioid receptor s. Our results suggest that tramadol could be a good choice for the tr eatment of pain in patients where immunosuppression may be particularl y contraindicated. (C) 1997 International Association for the Study of Pain. Published by Elsevier Science B.V.