Methods and findings in experimental and clinical pharmacology
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Methods Find Exp Clin Pharmacol · Nov 2005
Ondansetron does not block tramadol-induced analgesia in mice.
Tramadol is a weak opioid agonist and an inhibitor of the reuptake of noradrenaline and serotonin. This study was undertaken to assess a possible pharmacological interaction of ondansetron, a serotonin-3 (5-hydroxytryptamine-3, 5-HT3) antagonist, and tramadol in an animal model for acute pain. Sixty-three male albino mice were randomly given saline, tramadol (10, 20, and 40 mg kg(-1)), ondansetron (1, 2, and 4 mg kg(-1)), or ondansetron (1, 2, and 4 mg kg(-1)) and tramadol (20 mg kg(-1), given 10 min after ondansetron injection) intraperitoneally. ⋯ Tramadol (20 mg kg(-1)) and ondansetron (1, 2, and 4 mg kg(-1)) increased pain threshold levels at all doses (p < 0.001 for 1 and 2 mg kg(-1) ondansetron and p < 0.01 for 4 mg kg(-1) ondansetron). The pain threshold levels of mice given tramadol (20 mg kg(-1)) alone or tramadol and ondansetron (p > 0.05 for 1, 2, and 4 mg kg(-1)) were similar. Our results indicate that ondansetron-a 5-HT3 selective antagonist-does not decrease the analgesic effectiveness of tramadol in mice, which may be the result of different mechanisms involving 5-HT3 receptors.