Acute non-hypersensitivity adverse reactions following intravascular administration of contrast agents in adult patients.

Acute adverse drug reactions (ADR) to contrast agents have historically been divided in Type A (toxic/physiologic) reactions and Type B (hypersensitivity) reactions. Acute Type A adverse reactions are relatively uncommon after administration of iodine-based contrast media and gadolinium-based contrast agents, and rare after ultrasound contrast agents. Most acute Type A reactions are transient, mild, and of limited clinical consequence. Across all types of contrast agent (CA) classes, nausea and vomiting are the most frequently reported Type A reactions. In most cases, these reactions are caused by chemotoxicity and/or hyperosmolarity. Management of mild to moderate Type A reactions to contrast agents is often symptomatic and supportive, however, more severe Type A reactions need specialist treatment. We critically examined acute Type A ADR and nonspecific reactions following CA administration (labelled "physiologic" in the American College of Radiology classification) and propose a classification into three reaction types: acute non-hypersensitivity ADR, delayed Type A ADR, and Type B (hypersensitivity) ADR. This can facilitate accurate assessment and reporting of ADR to contrast agents.