Mixed opioid--mixed message?

By exposing the mu-receptor (MOP-R) to more than one exogenous ligand, the administration during general anaesthesia of more than one opioid with principal action on the receptor may confound and lead to complications or unexpected outcomes. The giving of such a 'mixed message' can result in respiratory depression, excess sedation and delayed recovery to an unusual degree. We present a case of apparent extreme opioid sensitivity and discuss a possible mechanism. Such occurrences may be more common than previously realised.