The Collaborative International Dictionary of English v.0.48:

Narcosis \Nar*co"sis\ (n[aum]r*k[=o]"s[i^]s), n. [NL., fr. Gr.
   na`rkwsis. See Narcotic.] (Med.)
   Privation of sense or consciousness, due to a narcotic.
   [1913 Webster]

WordNet (r) 3.0 (2006):

narcosis
    n 1: unconsciousness induced by narcotics or anesthesia

Moby Thesaurus II by Grady Ward, 1.0:

43 Moby Thesaurus words for "narcosis":
   analgesia, anesthesia, callousness, catalepsy, coma, deadness,
   dullness, electronarcosis, encephalitis lethargica, high,
   impassibility, imperception, imperceptiveness, imperceptivity,
   impercipience, inconsiderateness, insensibility, insensibleness,
   insensitiveness, insensitivity, insentience, lethargy,
   narcohypnosis, narcolepsy, narcoma, narcotic stupor, narcotization,
   nod, numbness, obtuseness, pins and needles, sedation, shock,
   sleeping sickness, sopor, stupor, swoon, thanatosis, thick skin,
   trance, unfeeling, unfeelingness, unperceptiveness