Pre-Medication Policy

Guidelines for Planned Administration of Contrast Agents

Category	Details
Previous reaction to same class of contrast agent to be given	Mild: No premedication needed
	Moderate: Consider premedication (see below)
	Severe: Do not routinely give contrast (see below)*
	For any severity of prior reaction to the same class, switch to a different contrast agent within that class if the inciting agent is known and an alternative is available.
Previous reaction to different class of contrast agent to be given	No premedication
Previous reaction to other allergens (e.g., shellfish, peanuts, medications, etc.)	No premedication

*Unless in the opinion of the responsible health care professional and supervising radiologist, the potential benefits outweigh the risks i.e. emergency situations. In these instances, clinical provider should accompany the patient to radiology suite (whenever feasible) to aid in management if a repeat reaction occurs and exam should only be done in hospital or ED setting. Premedication is advised and use of alternate contrast agent when contrast agent that caused prior reaction is known.

Premedication with steroids and an antihistamine is recommended only for patients who have had a hypersensitivity reaction (HSR) to contrast of a similar class (iodinated agents used during CT are one class, gadolinium-based agents used during MRI are separate class) to the one planned to be given. Prophylaxis for those with reactions to other allergens is not necessary. This guideline has been drawn up based on the following information:

• Current estimated overall reaction risk in the general population of children and adults is less than 1% (in range of 0.2-0.6%) (Wang et al., Dillman et al.)
• Patients with a prior reaction to the same class of contrast agent being administered are known to be at highest risk for repeat reaction, 3 – 11% overall reaction rate with 2% break-through reaction rate even with pre-medication during CT (Mervak et al. Lasser et al).
• The standard of care in the United States was to premedicate patients with steroids and diphenhydramine to decrease risk of repeat contrast reaction in patients who have had a reaction in the past to a similar class contrast agent. The 2025 consensus statement on hypersensitivity reactions from the ACR/AAAAI (Wang, et al.) recommends premedication for patients with a history of severe HSR when there is no acceptable alternative study (see table below for reaction severity). For a history of a moderate reaction, premedication may be considered but is NOT always needed (shared decision-making approach between ordering provider, patient, and radiologist when needed, weighing risks versus benefits from an individualized standpoint, is recommended).
• An IV steroid regimen (Recommended regimen below) is likely non-inferior compared to a longer PO regimen and is therefore recommended in the ED and in-patient setting to expedite imaging when needed (Mervak et al).

Exclusions

• In certain clinical circumstances the urgency of a contrast enhanced CT or MRI may outweigh the benefits and time needed to complete approved premedication protocol, necessitating that contrast medium be given in absence of premedication or with a variation in the pre-treatment protocol (such as antihistamine only). This determination should be jointly agreed upon by supervising radiologist and ordering clinician and potentially the patient (if feasible) with documentation in medical record.

Hypersensitivity Reactions¹:

Hypersensitivity Reactions categorized as Mild, Moderate, or Severe

Mild	Moderate	Severe
Limited urticaria² / pruritis²	Diffuse/rapidly spreading urticaria / pruritis²	Diffuse edema, or facial edema with dyspnea, hypoxia
Nasal congestion, sneezing / conjunctivitis / rhinorrhea	Facial edema without dyspnea	Diffuse erythema with hypotension
Limited “itchy”/“scratchy” throat	Throat tightness or hoarseness without dyspnea	Laryngeal edema with stridor and/or hypoxia Wheezing /bronchospasm, with hypoxia “Anaphylactic shock” (hypotension + tachycardia)

¹ Physiologic reactions like nausea, vomiting, feeling of warmth do NOT require premedication and are considered a side effect not hypersensitivity response.
² If the urticaria/pruritis required medical treatment, it should be considered moderate severity.
3According to the 2025 ACR/AAAAI consensus statement, anaphylaxis to ICM should be considered when the acute onset of illness occurs within minutes after IV ICM administration and in the absence of other known allergens or triggers. In such situations, anaphylaxis is considered likely if any two or more of these criteria are met:

• Involvement of skin or mucosal tissue, or both
• Respiratory compromise
• Reduced BP or associated symptoms of end-organ dysfunction. (Note that severe hypotension may preclude the manifestation of any other anaphylaxis symptoms, and anaphylaxis should be considered when there is no other source for the acute onset of severe hypotension within minutes of IV ICM administration.)
• Significant or persistent vomiting and/or severe diarrhea. (These GI symptoms alone do not meet criteria for anaphylaxis and should be significantly more severe than typical quickly resolving vomiting that can be a side effect of ICM.)

References:

• Wang CL, Cohan RH, Ellis JH, Caoili EM, Wang G, Francis IR. Frequency, outcome, and appropriateness of treatment of nonionic contrast media reactions. AJR 2008; 191:409–415.
• Lasser EC, Berry CC, Mishkin MM, Williamson B, Zheutlin N, Silverman JM. Pretreatment with corticosteroids to prevent adverse reactions to nonionic contrast media. AJR 1994; 162:523–526.
• Mervak BM, Davenport MS, Ellis JH, et al. Breakthrough reaction rates in high-risk inpatients premedicated before contrast-enhanced CT. AJR 2015; 205:77-84.
• Dillman JR, Strouse PJ, Ellis JH, Cohan RH, Jan SC. Incidence and severity of acute allergic-like reactions to i.v. nonionic iodinated contrast material in children. AJR 2007; 188:1643-1647.
• Mervak BM, Cohan RH, Ellis JH, Khalatbari S, Davenport MS. Intravenous Corticosteroid Premedication Administered 5 Hours before CT Compared with a Traditional 13-Hour Oral Regimen. Radiology 2017; 285:425-433.
• American College of Radiology Contrast Manual. 2020.
• Wang C, Ramsey A, Lang D, Maria Copaescu A, Krishnan P, Kuruvilla M, Mervak B, Newhouse J, Sumkin A, Saff R. Management and Prevention of Hypersensitivity Reactions to Radiocontrast Media: A Consensus Statement from the American College of Radiology and the American Academy of Allergy, Asthma & Immunology. Radiology. 2025 May;315(2).

All premedication regimens will include one steroid and one antihistamine.

Adult Out-patients:

• 50mg prednisone PO 13, 7 and 1 hour before the injection.
• 10mg cetirizine (Zyrtec®) PO within 1 hour of the injection.
• Note: Zyrtec preferred for less drowsy option. 50mg diphenhydramine (Benadryl®) IV/PO within 1 hour of the injection is acceptable alternative.

Adult ED and In-Patients:

• 40mg methylprednisolone IV 4 hours before injection.
• Alternative: 200mg hydrocortisone IV 4 hours before injection.
• 50mg diphenhydramine (Benadryl®) IV within 1 hour of the injection OR 10mg cetirizine (Zyrtec®) PO within 1 hour of the injection.

Pediatric Out-patients (For patients less than 50kg):

• Prednisolone 0.7mg/kg (not to exceed 50mg) PO 13, 7 and 1 hour before the injection OR Prednisone 0.7mg/kg (not to exceed 50mg) PO 13, 7 and 1 hour before the injection.
• Antihistamine:
• Patient >6 months of age: cetirizine (Zyrtec®) PO within 1 hour of the injection (age-based dosing: see prescribing information).
• Note: Zyrtec preferred for less drowsy option. Diphenhydramine (Benadryl®) 1mg/kg PO (not to exceed 50mg) is acceptable alternative.
• Patient <6 months of age: Diphenhydramine (Benadryl®) 1mg/kg PO (not to exceed 50mg) within 1 hour of the injection.

Pediatric ED and In-Patients:

• Methylprednisolone 1mg/kg (not to exceed 40mg) IV 4 hours before injection.
• Alternative: Hydrocortisone 1mg/kg (not to exceed 200mg) IV 4 hours before injection.
• Diphenhydramine (Benadryl®) 1mg/kg IV (not to exceed 50mg) within 1 hour of the injection OR age-based dosing of cetirizine (Zyrtec®) PO within 1 hour of the injection.

Alternate premedication can be used if the patient is known to tolerate other classes of steroids or different antihistamine. If needed, allergy consult may be needed for proper skin prick testing to find a suitable alternate (in many cases, the patient is not allergic to the drug itself but an additive in the drug).

For allergies to Benadryl, alternate antihistamine can be used that patient is known to tolerate.

Possible PO alternate antihistamine is Claritin or Zyrtec 10mg PO 1h prior to IV contrast administration.

Possible PO alternate steroid regimen is 32 mg methylprednisolone 12h and 2h prior to IV contrast administration.