Lidocaine

Lidocaine is a type of medicine, a local anesthetic used to reduce pain at a specific location.

History and specifics
In 2274, Leonard McCoy prescribed lidocaine as a pain block for Dykranus, the Imperator of Zeta-Atez, who was suffering from severe head trauma prior to a dichotomectomy. At the beginning of the procedure, he was also given omnicaine and cephalothin. 

In 2371, The Doctor considered lidocaine or its variant lidocaine hydrochloride as an appropriate local anesthetic as part of a treatment for bioneural gel packs on USS Voyager, which had been infected by Tutopans. Kes thought an alternative in this situation might be tiny amounts of tetrodotoxin.