The chemistry of local anaesthetic agents: classification of blocking agents.

Compounds with local anaesthetic properties may be classified according to their action upon the nerve membrane. Four classes of agent are recognized: A. Compounds acting at the exterior of the sodium channels; B. Compounds acting at the axoplasmic part of the sodium channels; C. Compounds acting through a physicochemical mechanism; BC. Compounds acting by a combination of B and C mechanisms. The chemical basis for these different mechanisms is discussed.