The local anaesthetic activity of a benzotriazinium salt.

1 The local anaesthetic properties of 2-n-propyl-4-p-tolylamino-1,2,3-benzotriazinium iodide (TnPBI) were compared with those of lignocaine hydrochloride on intact and desheathed sciatic nerves of the frog, on the phrenic nerve-hemidiaphragm preparation of the rat, and by the intradermal wheal test in the guinea-pig. 2 Both TnPBI and lignocaine were more potent on desheathed than on intact sciatic nerves. The potency of TnPBI was affected more than that of lignocaine by the presence of the sheath in intact nerves. 3 Both drugs inhibited conduction in the rat phrenic nerve, as shown by the reduction in twitch tension of the diaphragm elicited by nerve stimulation. TnPBI also caused an initial augmentation of the twitch tension of the diaphragm when applied directly to the muscle. 4 TnPBI was shown to be approximately twice as potent as lignocaine by the guinea-pig intradermal wheal test. 5 These results are discussed in view of the known effects of TnPBI on intracellular calcium storage.