1. Clinical Overview
Iohexol is a non-ionic, low-osmolar, water-soluble iodinated contrast medium used for intravascular and intrathecal radiographic procedures. The 300 mg Iodine/mL concentration is a standard strength for various diagnostic imaging studies. It provides excellent radiographic contrast with a favorable safety profile due to its low osmolality, reducing the risk of adverse reactions compared to older ionic agents.
| Onset | Duration | Bioavailability |
|---|---|---|
| Immediate upon intravascular administration; peak radiographic contrast occurs within seconds to minutes. | Contrast effect is transient, typically lasting for the duration of the imaging procedure (minutes). Pharmacokinetic presence in plasma has a half-life of approximately 2 hours in patients with normal renal function. | 100% (when administered intravascularly or intrathecally; not administered orally for systemic effect). |
2. Mechanism of Action
Iohexol is a radiopaque contrast agent. It contains iodine atoms (47% by weight) which effectively absorb X-rays. When introduced into body cavities, vessels, or the subarachnoid space, it attenuates X-rays to a greater degree than surrounding tissues, creating a contrast difference that allows visualization of anatomical structures and functional assessment (e.g., blood flow, patency) on radiographic or CT images.
3. Indications & Uses
- Intravascular: Angiography (cerebral, coronary, peripheral, visceral)
- Intravascular: Computed Tomography (CT) for enhancement of body structures (head, chest, abdomen, pelvis)
- Intravascular: Excretory Urography/Intravenous Pyelography (IVP)
- Intrathecal: Lumbar, Thoracic, Cervical, and Total Columnar Myelography
4. Dosage & Administration
Adult Dosage: Dose is highly variable and depends on procedure, patient weight, and imaging modality. Examples: CT of body: 50-150 mL (15-45g I); Angiography: Varies by vessel; Myelography: 10-15 mL (3-4.5g I). The 300 mg I/mL strength is commonly used for CT, IVP, and angiography.
Administration: For intravascular use: Administer as a bolus injection or controlled infusion using a power injector for CT. Strict aseptic technique. Warm to body temperature if large volume. For intrathecal use: MUST be preservative-free formulation only. Administered via lumbar puncture under strict aseptic conditions by trained specialist. Patient must remain with head elevated post-procedure.
5. Side Effects
Common side effects may include:
- Sensation of warmth/flushing (especially with rapid injection)
- Mild nausea
- Metallic taste in mouth
- Pain at injection site
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Metformin | Risk of lactic acidosis if contrast-induced nephropathy occurs. Must withhold metformin prior to and after procedure per protocol. | High |
| Interleukin-2 (IL-2) | Increased risk of delayed hypersensitivity reactions to contrast media. | Moderate |
| Beta-blockers (e.g., Propranolol) | May blunt response to treatment of anaphylactoid reactions (e.g., to epinephrine) and increase risk of bronchospasm. | Moderate |
| NSAIDs (e.g., Ibuprofen) | May potentiate nephrotoxic effects, increasing risk of CIN. | Moderate |
| Diuretics (e.g., Furosemide) | May increase risk of nephrotoxicity and dehydration. | Moderate |
7. Patient Counselling
- DO inform your doctor about all allergies, especially to iodine, shellfish, or previous contrast reactions.
- DO inform your doctor about all medications, especially metformin, and kidney problems.
- DO follow pre-procedure instructions regarding fasting and hydration.
- DO inform the radiologist if you are or could be pregnant.
- DONT drive immediately after the procedure if you feel dizzy or unwell.
- DONT hesitate to report any unusual sensations (itching, shortness of breath, swelling) during or after the injection.
8. Toxicology & Storage
Overdose: Symptoms are extensions of side effects: Severe renal impairment/failure, cardiovascular overload leading to pulmonary edema, seizures (especially with intrathecal overdose), severe anaphylactoid reactions, electrolyte imbalances.
Storage: Store at room temperature (15-30°C). Protect from light. Do not freeze. Keep the vial in the outer carton. The solution should be clear and colorless to pale yellow. Do not use if discolored or if particulate matter is present. For single use only; discard any unused portion.