Lexorin

Lexorin was a drug utilized during the late 23rd century that was developed to alleviate symptoms of malaise and/or multiple personality disorder in those who experienced a Vulcan mind meld, or who carried a Vulcan katra prior to its placement on Mount Seleya.

James T. Kirk administered a dose of lexorin to Leonard McCoy to help him feel well enough to travel with Spock's katra to Vulcan.