What is a local anesthetic and what is the link with cocaine?
A local anesthetic is a substance that inhibits pain (anesthesia) locally by blocking nerve messages (nerve conduction) and therefore stopping the excitement of the nerve ending with pain receptors. Cocaine, found indigenously in The Andes, West Indies and Java, was the first local anesthetic to be discovered. It is also the only naturally occurring local anesthetic. 

All subsequent local anesthetics are synthetically derived using Cocaine as a template; the idea being to reduce or eliminate adverse effects of cocaine whilst maintaining or increasing the anesthetic effect and the time of anesthesia.

Examples of synthetic local anesthetics include Procaine (sold under the name Novocaine) and Lignocaine or Lidocaine (sold under the name Xylocaine).
