The antinociceptive activity of drugs with sodium channel-blocking effect has been shown in a variety of studies. Flecainide, a sodium channel blocker, is an anti-arrhythmic agent belonging to IC class. Although the antinociceptive effects of flecainide have been demonstrated in a few animal pain models and clinical trials, the proarrhythmic effect of systemic flecainide has limited its usage while its role in nociceptive transmission at the spinal level has not been evaluated. The purpose of this study was to evaluate the effect of intrathecal flecainide on antinociception and hemodynamics. Flecainide was administered via an intrathecal catheter. Formalin test was used as an animal pain model, and blood pressure and heart rate were measured using an intra-arterial catheter in the tail artery. Intrathecal flecainide reduced pain behaviors in a dose-dependent fashion in both phase 1 and phase 2 in the formalin test only when administered before the formalin injection. In contrast, after the formalin injection intrathecally-administered flecainide did not produce a reduction in pain behaviors in phase 2 at the highest dose. In addition, intrathecal flecainide did not cause any significant hemodynamic changes in the rats.

KeywordsAntinociception; Intrathecal flecainide? Sodium -channel blocker; -Formalin- test; Hemodynamics; Sprague-Dawley rat