The local antinociceptive actions of nonsteroidal antiinflammatory drugs in the mouse radiant heat tail-flick test.

BACKGROUND: While many preclinical models detect the analgesic activity of nonsteroidal antiinflammatory drugs (NSAIDs), the radiant heat tail-flick response has repeatedly been insensitive to this class of drugs. As the tail-flick test involves nociceptive processing at spinal circuits with supraspinal modulation, it seems reasonable to assume that the NSAIDs should not modify strong nociceptive stimuli, since the primary site of action of NSAIDs is likely to be in the periphery. METHODS: We injected 3-300 mug of diclofenac, dipyrone, ketorolac, lysine acetyl salicylate, and sodium salicylate intradermally into mice tails and evaluated the tail-flick response to radiant heat. These results were compared with intraperitoneally injected controls. We also evaluated the ability of naloxone to reverse the observed effects. RESULTS: Intradermal injection of each NSAID produced a dose-dependent increase in tail-flick latency. Intraperitoneal NSAIDs injection produced no antinociceptive effects. Naloxone pretreatment had no effect on the antinociceptive effects of intradermal diclofenac, ketorolac, lysine acetyl salicylate, and sodium salicylate. Naloxone completely blocked the antinociceptive effects of intradermal dipyrone. CONCLUSIONS: Local, but not systemic, administration of NSAIDs produced antinociception in the tail-flick thermal assay. The endogenous opioid system contributes to the peripheral antinociceptive effects of dipyrone, but not to that of diclofenac, ketorolac, lysine acetyl salicylate, or sodium salicylate, suggesting differences in the mechanisms of action among the NSAIDs.

Airway smooth muscle relaxations induced by dipyrone.

BACKGROUND: Dipyrone differs from other nonsteroidal anti-inflammatory drugs with a distinctive spasmolytic effect; however, the mechanism of action is not clear yet. The possible mechanism behind this effect was investigated on airway smooth muscle tone in vitro. METHOD: The effect of dipyrone on inositol phosphate (IP) accumulation was evaluated on guinea pig trachea smooth muscle. Changes in intracellular free calcium levels and IP accumulation were evaluated in LTK8 cells. RESULTS: Dipyrone (0.01, 0.1, 1 mmol/l) had a relaxing effect on histamine (0.02 mmol/l)- and adenosine triphosphate- (ATP) (0.01 mol/l)-induced contractions, but not potassium chloride (KCl)-stimulated contractions. This relaxing effect was not observed with indomethacin. Indomethacin did not inhibit the relaxation response of dipyrone. In isolated tracheal smooth muscle, histamine- (0.02 mmol/l) and ATP (0.01 mmol/l)-induced IP accumulation was significantly inhibited by dipyrone (1 mmol/l). ATP (0.01 mmol/l)-induced IP accumulation was also significantly inhibited by dipyrone (0.01 mmol/l) in LTK8 cells. Dipyrone inhibited ATP-induced (0.01 and 0.1 mmol/l) intracellular calcium increase in LTK8 cells. CONCLUSION: Inhibition of the release of intracellular Ca(2+) may play a role in the smooth muscle relaxing effect of dipyrone. The inhibitor effect of dipyrone on IP accumulation may be due to direct inhibition of phospholipase C (PLC) or impairment of the activation of PLC by G protein-coupled receptor (GPCR).

Does dipyrone have any effect on respiratory function in COPD patients?

OBJECTIVE: Dipyrone (Novalgin) is an effective analgesic, antipyretic agent also with spasmolytic effects on various types of smooth muscles. It has recently been reported that dipyrone relaxes tracheal smooth muscle of guinea pig. In this present study, we aimed to investigate whether this and previously reported in vitro results have any consequences on the respiratory function of normal healthy volunteers and chronic obstructive pulmonary disease (COPD) patients. METHODS: In this one-centered, non-randomized, non-comparative, open labelled study, 15 normal healthy volunteers and 15 stable COPD patients, with partially reversible bronchospasm, diagnosed according to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) criteria were enrolled in the study at the time they had any indication of dipyrone use. The spirometric tests were performed by a portable notebook and Medikro Spiro2000 spirometry programme-software 1.6 version, before 30, 60, 90, and 120 min after 20 mg/kg of orally dipyrone intake. Groups were compared with the General Linear Model Repeated Measures analysis of variance. RESULTS: None of the spirometric parameters evaluated showed any significant differences when compared with the baseline values in both groups. CONCLUSION: While dipyrone had no bronchodilator effects on either COPD patients or normal volunteers, it also did not impair the spirometric parameters. Since COPD is a disease characterized by a progressive and largely irreversible airflow limitation, dipyrone has no observable bronchodilator effect. However, since dipyrone does not impair the pulmonary function, it can be used safely in COPD patients when there is an indication.