An anesthetic is a drug that causes anesthesia—reversible loss of sensation. These drugs are generally administered to facilitate surgery. A special anesthetic was used to sedate a symbiote that had infested Major Charles Kawalsky. (SG1: "The Enemy Within")
Stargate Command, the Atlantis expedition and the Destiny expedition all use some form of anesthetic in surgical situations. Dr. Carson Beckett used anesthetic on Ronon Dex when he was removing the Wraith tracker from him. (SGA: "Runner")