A method of treating a disease, disorder, or condition associated with metachromatic cell activation in a subject, said method comprising administering to a subject in need thereof a therapeutically effective amount of a composition comprising an NK-1 receptor inhibitor and an inhibitor of metachromatic cell activation, wherein the NK-1 receptor inhibitor is not a compound encompassed by Formula I, or Casopitant/GW679769 ((2R,4S)-4-(4-acetylpiperazin-1-yl)-N-{(1R)-1-[3,5-bis(trifluoromethyl)=phenyl]ethyl}-2-(4-fluoro-2-methylphenyl)-N-methylpiperidine-1-carboxamide).