antinociception

noun

an·​ti·​no·​ci·​cep·​tion ˌant-i-ˌnō-si-ˈsep-shən, ˌan-ˌtī- 

: the action or process of blocking the detection of a painful or injurious stimulus by sensory neurons

Compared with systemic narcotic analgesia, intraspinal narcotic antinociception has a longer duration.

—Dennis W. Coombs, The Journal of the American Medical Association

antinociceptive

-ˌnō-si-ˈsep-tiv 

adjective

… the antinociceptive action of morphine and endogenous opiates apparently proceeds by opening of the same class of neuronal potassium channels blocked by apamin.

—David Gurwitz, The Lancet