Opioid-induced hypersensitivity reactions – an update

Opioid analgesics have been used since ancient times in the treatment of chronic pain, nowadays also playing an important role in general anaesthesia. Usually, opioid analgesics are well tolerated substances; however, hypersensitivity reactions have been reported. These are more frequently observed during anaesthetic induction, despite their extensive use in chronic pain management. Allergy diagnosis includes a rigorous history, skin prick and intradermal tests using the adequate non-irritant concentrations, and subsequently a carefully supervised drug challenge test. Regarding the evaluation of a hypersensitivity reaction, the allergist must take into account the ability of these substances to degranulate mast cells and the structural similarities between members of the class that may make it difficult to select a therapeutic alternative. The lack of validated protocols and the risks of the procedure complicate the diagnostic approach and the choice of a suitable alternative, leading to overdiagnosis of opioid allergy and to ineffective pain management.