What is the recommended pretreatment regimen for patients with a history of contrast (intravenous contrast media) allergy?

Pretreatment Regimen for Patients with History of Contrast Allergy

For patients with a history of anaphylactoid reaction to contrast media, the recommended pretreatment regimen is 50 mg of prednisone administered 13 hours, 7 hours, and 1 hour before the procedure, plus 50 mg of diphenhydramine 1 hour before the procedure. 1

Standard Pretreatment Protocol

For non-emergency procedures in patients with prior contrast reactions:

• Oral regimen (preferred):

  • Prednisone 50 mg at 13 hours, 7 hours, and 1 hour before contrast administration 1
  • Diphenhydramine 50 mg 1 hour before contrast administration 1
  • In practice, many institutions use 60 mg of prednisone the night before and morning of the procedure, plus 50 mg of diphenhydramine 1 hour before the procedure 1

• Efficacy:

  • This regimen reduces recurrence rates of anaphylactoid reactions from 16-44% to nearly zero 1
  • Breakthrough reaction rates with premedication are still 3-4 times higher than the general population (2.1% vs 0.6%) 2

Emergency Pretreatment Protocol

For patients requiring urgent contrast administration:

• Intravenous regimen:
  • Hydrocortisone 200 mg IV immediately and every 4 hours until procedure completion 3
  • Diphenhydramine 50 mg IV 1 hour before the procedure 3
  • Consider IV steroids such as methylprednisolone 80-125 mg or hydrocortisone sodium succinate 100 mg 1

Additional Considerations

• Agent switching:

  • Switching to a different contrast agent (when the culprit agent is known) may be more effective than premedication alone 1
  • For patients with severe reactions, consider alternative non-contrast studies when possible 1

• Severity-based approach:

  • For mild to moderate previous reactions: Agent switching is recommended when feasible 1
  • For severe previous reactions: Consider alternative studies first; if contrast is necessary, use both agent switching AND premedication 1

• Setting:

  • Patients with history of severe reactions should be treated in a hospital setting with rapid response team availability, regardless of premedication 1

Common Pitfalls to Avoid

• Do not premedicate based solely on:

  • Shellfish or seafood allergy 1
  • Iodine allergy 1
  • Allergy to gadolinium-based contrast agents 1
  • Delayed contrast reactions 1

• Number needed to treat:

  • An estimated 69 patients must be premedicated to prevent one reaction of any severity 2
  • An estimated 569 patients must be premedicated to prevent one severe reaction 2

Risk Factors for Breakthrough Reactions

• Younger age 2
• Multiple indications for premedication 2
• Previous severe reaction 1, 4

For optimal outcomes, use a combination approach of both premedication AND contrast agent switching in high-risk patients, particularly those with history of moderate to severe reactions 1, 4.