The antinociceptive effect of ribavirin, an antiviral drug, was studied after systemic injection using several pain tests in mice. In the hot-plate test of thermal pain, capsaicin-induced chemogenic pain, formalin test and abdominal stretching assay induced by the i.p. injection of 0.6% acetic acid, ribavirin produced a dose-related reduction in nociceptive responses. The visceral antinociceptive effect of ribavirin was unaffected by co-treatment with yohimbine, atropine or theophylline, but partially reversed by naloxone. Antinociception by ribavirin was augmented by treatment with prazosin, doxazosin, propranolol, guanethidine, glibenclamide, baclofen, indomethacin or cysteamine. Further, the ribavirin induced antinociception was enhanced by D2 receptor antagonists haloperidol, sulpiride, clozapine or domperidone and by the dopamine D2 receptor agonist bromocryptine. Ribavirin did not exhibit depression-like effect, nor it influenced the effect of amitriptyline in the forced swimming test. It did not impair cognitive performance in the Morris water Maze test. The present data demonstrate that ribavirin administered via systemic route possesses visceral and thermal anti-nociceptive properties. The ribavirin analgesic effect was partially reversed by naloxone, an opioid antagonist.