Melanex

Melenex is an anesthetic carried in 2260s Starfleet medkits.

In 2269, Doctor McCoy used melenex to make Spock appear ill, fooling the computer which controlled the Shore Leave Planet. McCoy described the effects of melenex as, "brief unconsciousness and temporary skin discoloration", adding that "it looks worse than it is."

Once the doctor had dosed the Spock with 10 ccs of melenex by hypospray, McCoy told Spock that it took ten seconds to take affect, before rendering the Vulcan unconscious for less than five minutes. (TAS: "Once Upon a Planet")