ISOPAQUE 280
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ISOPAQUE 280 (ISOPAQUE 280).
Isopaque 280 (metrizoate) is an ionic, high-osmolar iodinated radiocontrast agent that attenuates X-rays by increasing the density of tissues where it distributes, thereby enhancing vascular and organ visualization during imaging.
| Metabolism | Metrizoate undergoes minimal metabolism; it is primarily excreted unchanged by glomerular filtration. |
| Excretion | Renal: approximately 95% of the dose is excreted unchanged in the urine within 24 hours via glomerular filtration. Fecal: <5%; biliary excretion is negligible. |
| Half-life | Terminal elimination half-life is 1.5–2 hours in patients with normal renal function; prolonged to >10 hours in severe renal impairment, requiring dose adjustment. |
| Protein binding | <5% bound to plasma proteins (primarily albumin). |
| Volume of Distribution | Approximately 0.2–0.3 L/kg, consistent with distribution primarily in extracellular fluid and minimal tissue penetration. |
| Bioavailability | Only administered intravenously or intra-arterially; bioavailability is 100% by these routes. Not orally bioavailable. |
| Onset of Action | Intravenous: immediate (<1 minute) for contrast enhancement. Intra-arterial: within seconds of injection. Not administered by other routes. |
| Duration of Action | Intravenous: contrast effect lasts 5–15 minutes for CT imaging; arterial injection may persist 2–4 minutes. Clinical use limited to imaging procedure duration. |
Iohexol (ISOPAQUE 280) is administered intravenously, intra-arterially, or by other appropriate routes. Typical adult dose for CT imaging: 50–150 mL (concentration 280 mg I/mL) as a bolus or infusion. For angiography: 5–80 mL per injection, depending on procedure. Repeat doses may be given up to a total of 350 mL.
| Dosage form | INJECTABLE |
| Renal impairment | Contraindicated in patients with severe renal impairment (eGFR <30 mL/min/1.73 m²) due to risk of contrast-induced nephropathy. For eGFR 30–59 mL/min/1.73 m², use minimum necessary dose, ensure adequate hydration, and consider alternative imaging. No specific dose reduction established; avoid repeated or high-dose procedures. |
| Liver impairment | No specific dose adjustments for hepatic impairment. Use caution in severe hepatic disease due to potential for altered fluid balance and decreased clearance. Child-Pugh class has no direct correlation; monitor renal function closely. |
| Pediatric use | Weight-based dosing for iohexol 280 mg I/mL: 0.5–2 mL/kg (140–560 mg I/kg) depending on imaging need. Maximum total dose: 3 mL/kg. Administer as intravenous bolus or infusion. Reduce dose in neonates and infants (1–2 mL/kg). |
| Geriatric use | Elderly patients may have reduced renal function; assess eGFR before administration. Use lowest effective dose, ensure adequate hydration, and monitor for adverse reactions. No specific dose reduction based on age alone, but adjust for renal impairment. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ISOPAQUE 280 (ISOPAQUE 280).
| Breastfeeding | Minimal excretion into breast milk. M/P ratio not established for metrizoate. Theoretical risk of neonatal hypothyroidism if high doses used, but amount transferred is negligible after standard doses. Manufacturer recommends discontinuation of breastfeeding for 24-48 hours post-administration, though ACR guidelines suggest no interruption necessary. |
| Teratogenic Risk | Contrast media like Isopaque 280 (metrizoate) are generally considered low risk for teratogenicity. No evidence of structural anomalies in humans, but minimal data in first trimester. Second and third trimester: theoretical risk of neonatal hypothyroidism from free iodide release; however, metrizoate is ionic and releases less free iodide than nonionic agents. Risk versus benefit must be assessed. |
■ FDA Black Box Warning
Not available (no FDA boxed warning identified for this agent).
| Serious Effects |
["Hypersensitivity to metrizoate or any component of the formulation","Previous anaphylactic reaction to any iodinated contrast agent (absolute)","Severe hyperthyroidism or thyrotoxic crisis (relative)","Anuria or severe renal impairment (relative, depending on benefit-risk)"]
| Precautions | ["Risk of acute kidney injury, especially in patients with pre-existing renal impairment, dehydration, or diabetes mellitus.","Severe hypersensitivity reactions (anaphylaxis) can occur; premedication may be considered for high-risk patients.","Increased risk in patients with history of allergy, asthma, or prior contrast reaction.","Thyrotoxicosis may be precipitated in patients with hyperthyroidism or multinodular goiter.","Extravasation may cause local tissue injury."] |
| Food/Dietary | No specific food interactions. However, patients are often advised to maintain adequate hydration with clear fluids. Avoid alcohol for 24 hours post-procedure due to potential additive nephrotoxic effects. |
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| Fetal Monitoring | Monitor maternal renal function and hydration status. Fetal monitoring: Assess for signs of hypothyroidism if high cumulative dose near term. No routine fetal monitoring required for standard diagnostic use. |
| Fertility Effects | No known adverse effects on fertility. Animal studies show no impairment of reproductive function. No human data suggesting negative impact. |
| Clinical Pearls | ISOPAQUE 280 (iohexol) is a nonionic, low-osmolar iodinated contrast medium. Pre-warming to body temperature reduces viscosity and improves patient comfort. Hydration with normal saline before and after administration is critical to prevent contrast-induced nephropathy. Screen for history of allergic reactions to contrast media; premedication with corticosteroids and antihistamines may be considered for high-risk patients. Avoid extravasation; if occurs, treat with elevation, cold compresses, and monitoring for compartment syndrome. Metformin should be withheld for 48 hours post-procedure and restarted only after renal function is stable. |
| Patient Advice | Inform your doctor if you have any allergies, especially to contrast media or iodine. · Tell your doctor if you have kidney disease, diabetes, asthma, or are taking metformin. · You may feel a warm sensation, metallic taste, or nausea during injection; these are common. · Drink plenty of fluids before and after the procedure to protect your kidneys. · If you experience hives, difficulty breathing, or swelling after the injection, seek emergency help immediately. |