The Collaborative International Dictionary of English v.0.48:

Devitalize \De*vi"tal*ize\, v. t.
   To deprive of life or vitality. -- De*vi`tal*i*za"tion, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

devitalize
    v 1: sap of life or energy; "The recession devitalized the
         economy" [syn: devitalize, devitalise] [ant:
         vitalise, vitalize]

Moby Thesaurus II by Grady Ward, 1.0:

51 Moby Thesaurus words for "devitalize":
   abate, afflict, attenuate, blunt, castrate, cramp, cripple, damp,
   dampen, deaden, debilitate, demasculinize, deprive, derange, desex,
   desexualize, disable, disorder, dry up, dull, effeminize,
   emasculate, enervate, enfeeble, etiolate, eviscerate, exhaust,
   extenuate, gruel, hospitalize, incapacitate, indispose, invalid,
   lay low, lay up, mitigate, rattle, reduce, sap, shake, shake up,
   sicken, soften up, sterilize, unbrace, undermine, unman, unnerve,
   unstrengthen, unstring, weaken