Iohexol
5-[acetyl(2,3-dihydroxypropyl)amino]-1-N,3-N-bis(2,3-dihydroxypropyl)-2,4,6-triiodobenzene-1,3-dicarboxamide
Also known as: Omnipaque · WIN-39424 · iohexolum · ioheksolis
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Estimate GFR (2-4 sample method) | 129-658 mg/kg | IV | Single dose | — | 🌎 NA |
| Estimate GFR (single sample method) | 90 mg iodine content/kg in non-azotemic animals and 45 mg iodine content/kg in azotemic animals | IV | Single dose | — | 🌎 NA |
| Contrast agent for suspected GI perforation | 700-875 mg Iodine/kg, 10 mL/kg | PO | Single dose | — | 🌎 NA |
- Estimate GFR (2-4 sample method): Given over a minute. Lower doses may result in plasma concentrations too low for accurate analysis.
- Estimate GFR (single sample method): Samples drawn at 120 min to assess validity of single-sample method.
- Contrast agent for suspected GI perforation: Best administered via orogastric tube. Radiographs obtained immediately, then at 15, 30, and 60 minutes.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Estimate GFR (single sample method) | 90 mg iodine content/kg in non-azotemic animals and 45 mg iodine content/kg in azotemic animals | IV | Single dose | — | 🌎 NA |
| Contrast agent for suspected GI perforation | 1:3 dilution of iohexol 240 at 10 mL/kg of body weight | PO | Single dose | — | 🌎 NA |
- Estimate GFR (single sample method): Samples drawn at 120 min to assess validity of single-sample method.
- Contrast agent for suspected GI perforation: Best administered via nasogastric/nasoesophageal tube.
Birds
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Contrast agent (GI abnormalities, transit time) | estimated crop volume of 25-30 mL/kg. Iohexol may be diluted 1:1 with water | PO | Single dose | — | 🌎 NA |
- Contrast agent (GI abnormalities, transit time): Administered directly into the crop by gavage. Retrograde administration directly into the cloaca may help evaluate cloacal abnormalities. Preferred over barium if perforation is suspected.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Iohexol is a non-ionic, low-osmolar contrast medium (LOCM) widely used in veterinary medicine for radiographic imaging and as a precise marker for estimating glomerular filtration rate (GFR).
- Imaging: Provides excellent radiopacity for myelography, excretory urography, angiography, and gastrointestinal studies.
- Safety Profile: Compared to older high-osmolar ionic contrast agents (e.g., diatrizoate), iohexol has significantly lower osmolality. This results in fewer adverse hemodynamic effects, less endothelial and erythrocyte damage, and reduced pain or heat sensation upon injection.
- Renal Function Testing: Because it is freely filtered by the kidneys without being secreted or reabsorbed, its clearance closely mimics inulin. It is highly stable in plasma and urine, making it an ideal, practical, and cost-effective marker for detecting early kidney disease when standard markers (BUN, creatinine) are insufficiently sensitive.
Mechanism of action
- Radiographic Contrast: Iohexol contains organic iodine atoms that absorb X-rays via the photoelectric effect → increases the radiopacity of the fluid or structure it fills → allows clear delineation of adjacent tissues on radiographs or CT scans.
- GFR Marker: Iohexol has negligible protein binding (<1%) and is freely filtered by the glomerulus → it is neither secreted nor reabsorbed by the renal tubules → nearly 100% is excreted unchanged in the urine within 24 hours. By measuring the rate of plasma disappearance over time, clinicians can accurately calculate the glomerular filtration rate (GFR).
Safety & warnings
Contraindications
- Prior hypersensitivity reaction to iohexol or iodine-containing products
Adverse effects
- Hypersensitivity reactions (rare)
- Nephrotoxicity (slight risk)
- Pain or heat sensation at injection site (less common than with ionic agents)
Precautions
Hypersensitivity: Always monitor for signs of anaphylaxis or allergic reactions, even though they are rare in veterinary patients.
- Nephrotoxicity: While the risk is low, use with caution in patients with pre-existing severe renal impairment or dehydration; ensure adequate hydration prior to intravascular administration.
- Pregnancy: FDA Category B. Animal studies have not demonstrated fetal risk, but use in late pregnancy carries potential theoretical risk to fetal thyroid function.
- Laboratory Interference: Prior use of iohexol can reduce the iodine-binding capacity of thyroid tissue for up to 2 weeks, interfering with iodine-dependent thyroid function tests.
Drug interactions
May cause additive prolongation of the QTc interval, though iohexol causes less prolongation than diatrizoate.
May alter binding to thyroid tissue for up to two weeks, affecting certain thyroid treatments or scans.
May increase the risk for lowering the seizure threshold, especially when iohexol is used intrathecally.
Monitoring
- Signs of hypersensitivity or anaphylaxis during and immediately after administration
- Renal function (if pre-existing impairment exists)
- Hydration status
Pharmacokinetics
Half-life
Absorption
Rapidly distributed throughout the circulation after intravascular administration.
Distribution
Volume of distribution (Vdss) in dogs is 221 mL/kg. Protein binding is very low (<1%). Distributed into milk in very low quantities.
Metabolism
Not significantly metabolized.
Elimination
Nearly 100% of a dose is excreted unchanged in the urine within 24 hours in patients with normal renal function. Mean clearance in dogs: 2.5-2.9 mL/kg/minute. Mean clearance in cats: 2.3-2.75 mL/kg/minute.
Overdose
Adverse effects of intravenous overdosage can be serious and life-threatening, primarily affecting the pulmonary and cardiovascular systems.
- Clinical Signs: Cyanosis, bradycardia, acidosis, pulmonary hemorrhage, convulsions, coma, and cardiac arrest.
- Treatment: Treatment is entirely supportive and symptomatic. Maintain airway, support ventilation, and manage cardiovascular collapse with appropriate fluids and vasopressors as needed.
Available products
Formulations
- Injection (preservative-free)
Human-labeled
- Iohexol Injection (preservative-free): 180 mg/mL, 240 mg/mL, 300 mg/mL & 350 mg/mL (organic iodine content) in various vials, bottles, syringes, or cartridges (Omnipaque)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store at room temperature 25°C (68°F); excursions permitted between 15°-30°C. Protect from light.
Client information
What is Iohexol? Iohexol is a specialized medical dye (contrast agent) used to help veterinarians see your pet's internal organs more clearly on X-rays or CT scans. It is also used as a highly accurate test to measure how well your pet's kidneys are working.
- Safety: This is a modern, "low-osmolar" contrast agent, meaning it is much gentler on the body and causes far fewer side effects than older dyes.
- What to Expect: If used for imaging, it may be given by mouth, injected into a vein, or placed into a specific body cavity. If used for kidney testing, it is injected into a vein, and a few blood samples are drawn over the next several hours to see how fast the kidneys clear it from the blood.
- Side Effects: Reactions are extremely rare in pets. However, watch for any signs of an allergic reaction (facial swelling, hives, difficulty breathing) or extreme lethargy, and contact your veterinarian immediately if these occur.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.