Opioid-induced itching: morphine sulfate and hydromorphone hydrochloride

We describe a case of severe morphine-induced itch unrelieved by antihistamines, which responded to a change to hydromorphone. The possible mechanisms of opioid-induced itch are briefly discussed. It is unclear if it is due to histamine release, an opioid-receptor mediated effect, or idiosyncratic drug reaction.