Anaphylaxis to intrathecal diamorphine

A 42-year-old male underwent a total hip arthroplasty under subarachnoid anaesthesia with intrathecal bupivacaine and diamorphine. Shortly after the start of surgery, he suffered an allergic reaction that, at first, was difficult to distinguish from the recognised side-effects of intrathecal diamorphine. Once the diagnosis was made, he was treated with adrenaline and made a full recovery. The serum concentration of mast cell tryptase approximately 1.5 h after the onset of the adverse incident confirmed an anaphylactic reaction. Skin prick testing several weeks later identified diamorphine as the likely causative agent, a drug overlooked initially as a potential cause. We believe this is the first report of intrathecal diamorphine causing anaphylaxis.