Therapeutic effect of cocaine
The local anaesthetic effect of cocaine has been known for some time and it was previously used in dentistry and ophthalmology. Cocaine prevents action potential generation by physically blocking sodium channels via two alternative mechanisms. The uncharged species reaches the blocking site within the channel via the membrane (hydrophobic pathway), while the charged species reaches the site via the open channel gate (hydrophilic pathway). The blockade prevents voltage-dependent Na+ conductance, which results in local nerve block.
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References
Local anaesthetics and other drugs that affect ion channels. In: Pharmacology, 4th edition. Rang HP, Dale MM and Ritter JM. Edinburgh, UK: Harcourt Publishers Ltd, 2001:634–645.