RESUMO
There are reports about a possible weak local anaesthetic activity of nicorandil, a potassium channel agonist (PCA). In addition, modification of local anesthetic activity of lignocaine by PCA is not clearly defined. The objective of the present study is to evaluate local anesthetic activity of nicorandil and to evaluate the influence of nicorandil on the efficacy and duration of local anesthesia by lignocaine. A total number of 84 albino rats of either sex were divided into 14 groups of 6 animals each. Two methods, sciatic nerve blockade and tail clip method were applied for the study. Control group received 0.2ml normal saline, whereas the study group received 0.2ml of 1% drug solution (lignocaine or nicorandil) combined with 0.9% sodium chloride. The results showed weak local anaesthetic activity with the higher dosages of nicorandil (10 mg/kg, 100mg/kg). Combination of nicorandil (1mg/kg, 10mg/kg and 100mg/kg) and lignocaine (5mg/kg) yielded synergistic results like decreased onset latency and prolonged reaction time. To conclude unquestionably there are multiple mechanisms involved for causation of local anesthetic effect by drugs like lignocaine. PCAs like nicorandil will influence the activity of these drugs as observed in the present study. Mechanism of this may be complex. Nicorandil may increase the plasma membrane permeability to potassium causing hyper polarization and moves the membrane potential away from the threshold required to generate an action potential.