Intraspinal opiates and itching: A new reflex?

Abstract

Facial itching is a common, unwelcome, and unexplained side effect of intraspinal opiates. Opiates release histamine from mast cells in body tissues, but it is not known whether histamine is wholly or even partly to blame for the itching referred so constantly and so specifically in the distribution of the trigeminal nerve. There is mounting evidence in favour of a central, enkephalinergic mechanism for some kinds of itch. Itching induced by butorphanol, a morphine-like analgesic that does not raise blood histamine concentrations, can be prevented by naloxone. Naloxone has also proved successful in the treatment of generalised itch in patients with liver disease. The authors report on three patients in whom facial itching provoked by intrathecal opiate responded to intravenous naloxone.