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Dipyrone, a pirazolone derivative, is a known analgesic drug with minor toxic effects associated with its administration. The aim of the present study was to determine the analgesic and antiinflammatory effects of dipyrone in a model of chronic inflammation (adjuvant-induced arthritis in rats). Hind-paw hyperalgesia was detected in arthritic rats from the 10th to the 16th day of observation. Edema development was maximum (twofold increase) at the 14th day of observation compared to control animals and reduced at the 16th day of observation. Dipyrone (1-50 mg/kg) dose-dependently reduced both hind-paw hyperalgesia and edema from arthritic rats. However, it was shown to be more potent as analgesic than antiinflammatory in the present model. In contrast, indomethacin (2 mg/kg) and dexamethasone (0.4 mg/kg) completely inhibited hind-paw hyperalgesia and edema development. Our results indicate that dipyrone reduced the hyperalgesia and edema in arthritic rats by a mechanism not involving release of prostaglandin-like substances. The possibility of dipyrone inducing analgesia in arthritic rats through a peripheral action supports the use of dipyrone as an alternative choice drug for the treatment of pain associated with arthritislike diseases in selected cases.

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Dipyrone, a non-steroidal anti-inflammatory agent, was anticonvulsant in three experimental epilepsy models. At a dose of 300 mg/kg i.p., dipyrone blocked the maximal hind limb extension in the electroshock model in Wistar rats, the tonic-clonic component of acute sound-induced seizures and the limbic component of audiogenic kindling in genetically susceptible Wistar-derived rats, all in 100% of the animals. In the electroshock model higher doses (400 and 500 mg/kg) were also effective but lower doses (100 and 200 mg/kg) were not. In this model dipyrone had no effect on the recovery of the righting reflex and intensified the postictal antinociception in a dose-dependent manner. Other non-steroidal anti-inflammatory agents such as indomethacin, diclofenac and aspirin had no anticonvulsant effect in the electroshock-induced seizures.