Some opioids can trigger the release of histamine from mast cells.
Manifestations:
(1) flushing
(2) decreased blood pressure
(3) increase in heart rate
(4) pruritis
(5) sweating
Factors:
(1) opioid administered - some opioids release more histamine than others
(2) dose of the opioid - the higher the dose, the greater the effect
(3) sensitivity of the patient
Opioids less likely to release histamine: oxycodone, oxymorphone, fentanyl
Differential diagnosis:
(1) IgE-mediated hypersensitivity reaction, including anaphylaxis
(2) hypersensitivity to another drug or excipient
