Pharmacology
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Comparative Study
Synergic antinociceptive interaction between tramadol and gabapentin after local, spinal and systemic administration.
The possible interaction between tramadol and gabapentin on formalin-induced nociception in the rat was assessed. Tramadol, gabapentin or a fixed-dose ratio combination of gabapentin and tramadol were administered peripherally, spinally and orally to rats, and the antinociceptive effect was determined in the 1% formalin test. Isobolographic analyses were used to define the nature of the interactions between drugs. ⋯ Although efficacy was not improved, local peripheral administration resulted in the highest increase in potency, being about tenfold. Spinal and systemic administration increased potency threefold. Data indicate that low doses of the tramadol-gabapentin combination can interact synergistically to reverse formalin-induced nociception and may represent a therapeutic advantage for clinical treatment of inflammatory pain.