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More than 75 million X-ray examinations are being performed annually using radiocontrast media (RCM). Contrast agents have been used for the imaging of anatomic boundaries and to explore normal and abnormal physiologic findings. RCMs are currently classified based on ion content, and in clinical practice, nonionic RCMs are preferred because they have a lower risk for hypersensitivity reactions. Adverse reactions to radiocontrast media range from itching associated with hives, to a life-threatening emergency such as anaphylaxis.
RCM reactions may be:
• Hypersensitivity reactions to monomeric ionic radiocontrast media
• Severe reactions
• Hypersensitivity reactions to nonionic radiocontrast media
Types of radiocontrast agents
• High osmolality ionic – Diatrizxoate Sodium (Hypaque); Iothalamate meglumine (Conray)
• Low osmolality ionic – Ioxaglate meglumine (Hexabrix)
• Low osmolality nonionic – Gadodoamide (Omniscan); Gadoteoridol (ProHance); Iodixanol (Visipaque); Iopamidol (Isovue); Iopromide (Ultravist); Ioversol (Optiray)
Contrast agents with higher osmolality are more likely to cause adverse reactions of all types. Renal toxicity is more often associated with exposure to high osmolality agents. Low osmolality agents are associated with less discomfort, and less hypersensitivity or anaphylactic type reactions.
Guidelines have been developed by the American College of Radiology for the use of low-osmolality nonionic agents. Based on these guidelines, nonionic agents should be used in patients who are at increased risk of adverse reactions, such as patients with asthma, multiple allergies, or diseases that could be aggravated by contrast material.
Risk factors for hypersensitivity reactions to radiocontrast media
• Female Gender
• Severe Cardiovascular Disease
• Previous reactions to RCM
• Drug Allergy
Types of hypersensitivity reactions to radiocontrast media
• Immediate – Ig-E mediated or non Ig-E mediated
• Non-immediate (Delayed)
Signs and symptoms of adverse reactions to radiocontrast media
• Acute reaction – within an hour of receiving contrast agent, severe reactions usually anaphylaxis
• Pain on injection
• Bradycardia and hypotension
• Rash, Urticaria
• Cough, Dyspnea, Bronchospasm
• Delayed reaction – occurs between 1 hour to 1 week after receiving contrast agent
• Rash and pruritus
• Severe skin reactions eg. Stevens Johnson syndrome
• Contrast Induced Nephropathy – direct renal toxicity
• Increased serum creatinine (>25 percent) within 3 days after receiving contrast agent
• Avoid use of ionic monomers, if possible, for those with risk factors.
• Consider alternate imaging techniques that do not require contrast agent use.
• Pretreatment with corticosteroids and antihistamines for prophylaxis of reactions to radiocontrast media as follows: (Modified from Greenberger and Patterson)
• Adequate hydration.
• Plasma Tryptase and Histamine
• Skin Testing
• Drug Provocation tests
• Symptomatic treatment.
• Antiemetics for nausea and vomiting.
• Corticosteroids and antihistamines for rash and pruritus.
• Intravenous fluids for hypotension.
• Epinephrine for anaphylaxis.
There are still many issues that need to be addressed and require further research to improve knowledge in this field of Radiocontrast media hypersensitivity reactions, including diagnostic tools, to achieve improved quality in patient’s care.
• Sanchez-Borges, M. MD etal. Controversies in Drug Allergy: Radiographic Contrast Media. JACI, Vol 7, 1: Jan 2019, 61-65.
• Clement, Olivier MD etal. Immediate Hypersensitivity to Contrast Agents. EClinical Medicine (Lancet) Vol 1, July 2018, 51-61
• Pasternak, Jeffrey J. MD; Williamson, Eric, MD. Clinical Pharmacology, Uses and Adverse Reactions of Iodinated Contrast Agents. Mayo Clinic Proc.
• Maddox, Thomas MD. Adverse Reactions to Contrast Material. Am Family Physician