THE ANALGESIC EFFECT OF PREGABALIN, A COMPARATIVE STUDY WITH MORPHINE

Abstract

this study was designed to assess and compare the effects of pregabalin and morphine on acute thermal pain and on nerve injury associated pain (chronic neuropathic pain). Methods: 72 male albino rats were divided into two major groups: group I (acute pain group) 30 rats divided into 5 equal subgroups (1)control, (2) pregabalin 30 mg/kg, (3)morphine 0.5 mg/kg, (4) pregabalin 60 mg/kg, (5)morphine 1mg/kg, and group II(chronic pain group) 42 rats were divided into 7 equal subgroups (1)sham operated, (2)control normal, (3) control postoperative, (4) pregabalin 30mg/kg, (5) morphine 0.5 mg/kg, (6) pregabalin 60 mg/kg, (7) morphine 1mg/kg. For acute pain the reaction times, which indicate the tolerability of the animals to acute thermal pain, was measured using analgesia meter. However chronic neuropathic pain was induced in experimental animals by unilateral ligation of the sciatic nerve in the thigh. Results: The result of the present study revealed that neither 30 nor 60 mg/kg pregabalin produced any significant effects on the tolerability of rats to acute thermal pain. On the other hand, pregabalin (30 and 60 mg/kg) markedly reversed allodynia and hyperalgesia in rats subjected to sciatic nerve ligation. The effect of pregabalin 30 mg/kg was noticed after 60 minutes and persist for 90 minutes but the higher dose (60 mg/kg) produced analgesic effect all over the experiment. On the other hand morphine 0.5 and 1 mg/kg significantly increased the tolerability of normal and sciatic nerve ligated rats to thermal nociception. The analgesic effect of morphine was more significant than that of pregabalin all over the experiments.
Conclusion: in contradiction to morphine, pregabalin was not effective for treatment of acute pain. Both pregabalin and morphine produced significant analgesic effect in neuropathic pain. The effect of morphine was more significant than that of pregabalin. Key words: Pregabalin, chronic neuropathic pain, morphine, sciatic nerve ligation.