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Title: Isobolographic analysis of the analgesic interactions between ketamine and tramadol
Authors: Chen, Y.
Chan, S.Y. 
Ho, P.C. 
Issue Date: 2002
Citation: Chen, Y., Chan, S.Y., Ho, P.C. (2002). Isobolographic analysis of the analgesic interactions between ketamine and tramadol. Journal of Pharmacy and Pharmacology 54 (5) : 623-631. ScholarBank@NUS Repository.
Abstract: Owing to different mechanisms of analgesia, we hypothesized that the combination of ketamine and tramadol could produce synergistic or additive antinociceptive effects. Swiss albino mice were administered intraperitoneally with ketamine, tramadol, a combination of ketamine and tramadol, or saline, and the resulting antinociceptive effects were tested in the mouse tail-flick and formalin tests. The potencies of the two drugs alone or in combination were obtained by fitting data to the Sigmoid Emax equation. Isobolographic analysis was performed to evaluate the interaction. CNS depression was also monitored. Results showed that tramadol exhibited apparent dose-dependent effects in the tail-flick test, and in phase 1 and phase 2 of the formalin test. Ketamine dose-dependently inhibited the phase 2 responses, but failed to modify the phase 1 and tail-flick responses. Combination of tramadol and ketamine produced significant synergistic interactions only in phase 2 of the formalin test (P < 0.05). The synergistic combinations also displayed less CNS depression than when an equianalgesic dose of ketamine was administered alone. We conclude that in the acute thermal or chemical pain model, ketamine is not effective and the net effect of ketamine and tramadol in combination was simply additive after systemic administration. However, the coadministration produced synergistic antinociception in the chemical-induced persistent pain model.
Source Title: Journal of Pharmacy and Pharmacology
ISSN: 00223573
DOI: 10.1211/0022357021778934
Appears in Collections:Staff Publications

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