drugs that block nerve conduction when applied locally to nerve Tissue in appropriate concentrations. They act on any part of the nervous system and on every type of nerve fibre. In contact with a nerve trunk, these anaesthetics can cause both sensory and motor paralysis in the innervated area. Their action is completely reversible. Nearly all local anaesthetics act by reducing the tendency of voltage-dependent sodium channels to activate. They are commonly used not only in the peripheral nervous system, but also for spinal anaesthesia. The many drugs that have local anaesthetic actions as a side effect but are not used for their local anaesthetic action are not included here.