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Radiographic Contrast Agents and Contrast Reactions


Mustafa A. Mafraji

, MD, Rush University Medical Center

Reviewed/Revised Nov 2023

Radiopaque contrast agents are often used in radiography and fluoroscopy to help delineate borders between tissues with similar radiodensity. Most contrast agents are iodine based.

Iodinated contrast agents may be

  • Ionic

  • Nonionic

Ionic contrast agents, which are salts, are hyperosmolar to blood. These agents should not be used for myelography or in injections that may enter the spinal canal (because neurotoxicity is a risk) or the bronchial tree (because pulmonary edema is a risk).

Nonionic contrast agents are low-osmolar (but still hyperosmolar relative to blood) or iso-osmolar (with the same osmolarity as blood). Newer nonionic contrast agents are now routinely used at nearly all institutions because they have fewer adverse effects.

The most serious contrast reactions are

  • Allergic-type reactions

  • Contrast nephropathy (renal damage after intravascular injection of a contrast agent)

Allergic-type contrast reactions

Reactions vary in severity:

  • Mild (eg, cough, itching, nasal congestion)

  • Moderate (eg, dyspnea, wheezing, slight changes in pulse or blood pressure)

  • Severe (eg, respiratory distress, arrhythmias such as bradycardia, seizures, shock, cardiopulmonary arrest)

  • A previous reaction to injected contrast agents

  • Asthma

  • Allergies

Treatment begins by stopping contrast infusion.

For mild or moderate reactions, diphenhydramine 25 to 50 mg IV is usually effective.

For severe reactions, treatment depends on the type of reaction and may include oxygen, epinephrine, IV fluids, and possibly atropine (for bradycardia).

In patients at high risk of contrast reactions, imaging tests that do not require iodinated contrast should be used. If contrast is necessary, a nonionic agent should be used, and patients should be premedicated with prednisone (50 mg orally 13 hours, 7 hours, and 1 hour before injection of contrast) and diphenhydramine (50 mg IV, IM, or orally 1 hour before contrast administration). If patients require imaging immediately, they can be given diphenhydramine 50 mg IV, IM, or orally 1 hour before injection of contrast and hydrocortisone 200 mg IV every 4 hours until the study is performed, preferably deferring imaging, if possible, until at least 2 doses of hydrocortisone have been administered (see American College of Radiology Manual on Contrast Media).

Contrast nephropathy

In contrast-induced nephropathy Contrast Nephropathy Contrast nephropathy is worsening of renal function after IV administration of radiocontrast and is usually temporary. Diagnosis is based on a progressive rise in serum creatinine 24 to 48 hours... read more , serum creatinine typically begins to increase within 24 hours after administration of IV contrast; it peaks between days 3 and 5 and returns to baseline within 7 to 10 days.

Common risk factors include the following:

  • A reduced dose of contrast

  • Use of an iso-osmolar agent

  • Hydration

Many hydration regimens exist. One regimen suggests administration of normal saline at 100 mL per hour for a duration of 6 to 12 hours before the contrast administration and continued for 4 to 12 hours following the contrast injection (see American College of Radiology Manual on Contrast Media).

Administration of N-acetylcysteine has been widely studied and has not been shown to be effective in preventing contrast-induced nephropathy (1 Reference Radiopaque contrast agents are often used in radiography and fluoroscopy to help delineate borders between tissues with similar radiodensity. Most contrast agents are iodine based. Iodinated... read more ).

Lactic acidosis

Because many protocols dealing with contrast agents and reactions are specific and continually updated, it is important to discuss such details with the imaging department.

Pearls & Pitfalls

  • Withhold metformin for 48 hours after IV contrast administration if acute kidney injury develops to avoid lactic acidosis, and restart metformin only after confirming kidney function has improved.


Drugs Mentioned In This Article

Drug Name Select Trade
Aid to Sleep, Alka-Seltzer Plus Allergy, Aller-G-Time , Altaryl, Banophen , Benadryl, Benadryl Allergy, Benadryl Allergy Children's , Benadryl Allergy Dye Free, Benadryl Allergy Kapgel, Benadryl Allergy Quick Dissolve, Benadryl Allergy Ultratab, Benadryl Children's Allergy, Benadryl Children's Allergy Fastmelt, Benadryl Children's Perfect Measure, Benadryl Itch Stopping, Ben-Tann , Children's Allergy, Compoz Nighttime Sleep Aid, Diphedryl , DIPHEN, Diphen AF , Diphenhist, DiphenMax , Dytan, ElixSure Allergy, Genahist , Geri-Dryl, Hydramine, Itch Relief , M-Dryl, Nighttime Sleep Aid, Nytol, PediaCare Children's Allergy, PediaCare Nighttime Cough, PediaClear Children's Cough, PHARBEDRYL, Q-Dryl, Quenalin , Siladryl Allergy, Silphen , Simply Sleep , Sleep Tabs, Sleepinal, Sominex, Sominex Maximum Strength, Theraflu Multi-Symptom Strip, Triaminic Allergy Thin Strip, Triaminic Cough and Runny Nose Strip, Tusstat, Unisom, Uni-Tann, Valu-Dryl , Vanamine PD, Vicks Qlearquil Nighttime Allergy Relief, Vicks ZzzQuil Nightime Sleep-Aid
Adrenaclick, Adrenalin, Auvi-Q, Epifrin, EpiPen, Epipen Jr , Primatene Mist, SYMJEPI, Twinject
Atreza, Atropine Care , Atropisol , Isopto Atropine, Ocu-Tropine, Sal-Tropine
Deltasone, Predone, RAYOS, Sterapred, Sterapred DS
A-Hydrocort, Ala-Cort, Ala-Scalp, Alkindi, Anucort-HC, Anumed-HC, Anusol HC, Aquaphor Children's Itch Relief, Aquaphor Itch Relief, Balneol for Her, Caldecort , Cetacort, Colocort , Cortaid, Cortaid Advanced, Cortaid Intensive Therapy, Cortaid Sensitive Skin, CortAlo, Cortef, Cortenema, Corticaine, Corticool, Cortifoam, Cortizone-10, Cortizone-10 Cooling Relief, Cortizone-10 External Itch Relief, Cortizone-10 Intensive Healing, Cortizone-10 Plus, Cortizone-10 Quick Shot, Cortizone-5 , Dermarest Dricort, Dermarest Eczema, Dermarest Itch Relief, Encort, First - Hydrocortisone, Gly-Cort , GRx HiCort, Hemmorex-HC, Hemorrhoidal-HC, Hemril , Hycort, Hydro Skin, Hydrocortisone in Absorbase, Hydrocortone, Hydroskin , Hydroxym, Hytone, Instacort, Lacticare HC, Locoid, Locoid Lipocream, MiCort-HC , Monistat Complete Care Instant Itch Relief Cream, Neosporin Eczema, NuCort , Nutracort, NuZon, Pandel, Penecort, Preparation H Hydrocortisone, Proctocort, Proctocream-HC, Procto-Kit, Procto-Med HC , Procto-Pak, Proctosert HC , Proctosol-HC, Proctozone-HC, Rectacort HC, Rectasol-HC, Rederm, Sarnol-HC, Scalacort, Scalpicin Anti-Itch, Solu-Cortef, Texacort, Tucks HC, Vagisil Anti-Itch, Walgreens Intensive Healing, Westcort
Acetadote, CETYLEV, Mucomyst, Mucosil Acetylcysteine
Fortamet, Glucophage, Glucophage XR, Glumetza, Riomet, RIOMET ER
NOTE: This is the Professional Version. CONSUMERS: View Consumer Version
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