Omnipaque 350
Omnipaque 350
Generic Name
Omnipaque 350
Mechanism
- Iodinated radiographic enhancer: High atomic number (iodine) of iohexol increases X‑ray attenuation, rendering vessels, organs, or contrast‑filled structures visible.
- Non‑ionic: Lacks charge‑bearing groups, reducing osmolality and subsequent fluid shifts, thus providing better tolerability compared to older ionic agents.
- Low‑osmolarity (300–350 mOsm/kg): Decreases the likelihood of adverse reactions associated with hyperosmolar contrast (e.g., tachycardia, hypertension).
Pharmacokinetics
- Absorption: 100 % via intravenous route.
- Distribution: Rapid extravasation into extracellular fluid; high tissue solubility.
- Metabolism: None – chemically inert within the body.
- Elimination: Primarily renal (≈70 % unchanged in urine).
- Half‑life ~2–3 h in patients with normal renal function.
- Reduced excretion in renal impairment; caution with eGFR < 30 mL/min/1.73 m².
Indications
- Computed Tomography (CT) – CT angiography, CT urography, CT of the brain/abdomen/pelvis.
- Intravenous Pyelography (IVP) – evaluation of urinary tract obstruction.
- Angiography & Interventional Radiology – diagnostic and therapeutic procedures.
- Hysterosalpingography – assessment of uterine cavity and fallopian tubes.
- Radiopaque liver/ biliary tree imaging – to delineate pathology.
Contraindications
- Contraindications:
- Known hypersensitivity to iohexol or iodinated contrast agents.
- Severe uncontrolled electrolyte imbalances.
- Warnings:
- Contrast‑induced nephropathy (CIN): increased risk in patients with diabetes, chronic kidney disease (CKD), or dehydration. Pre‑hydrate and consider nephroprotective agents.
- Iodine allergy: Rare, but can trigger anaphylaxis; maintain resuscitation equipment.
- Pregnancy: Category C. Use only if benefits outweigh risks.
- Precautions:
- Thyroid dysfunction: Monitor thyroid function in patients with pre‑existing thyroid disease due to iodine load.
- Acetazolamide: Contraindicated in patients with a history of hypersensitivity to acetazolamide (used in diuretic therapy), as both may alter renal handling of iohexol.
Dosing
| Study Type | Typical Dose | Volume | Dilution (if needed) |
| CT → Head/Body/Abdomen | 1.5–3 mL/kg | 100–120 mL | Dilute to 250–300 mL with saline (1 : 2) for rapid injection. |
| Angiography | 2–5 mL/kg (max 200 mL) | 100–200 mL | Dilute with saline to lower viscosity. |
| Hysterosalpingography | 10 mL | 10 mL | Dilute with sterile water to 50 mL. |
| Administration | |||
| • Route | IV (or intra‑vascular) | ||
| • Injection rate | 4–6 mL/s (CT) | ||
| • Post‑dose hydration | 1–2 L isotonic saline over 4‑6 h | ||
| • Monitoring | Vital signs, renal function |
Monitoring
- Baseline: Serum creatinine, eGFR, electrolytes, BP, HR.
- Periprocedural: BP, HR, oxygen saturation during injection.
- Post‑procedure:
- Monitor urine output for 12–24 h.
- Creatinine 24–48 h post‑contrast to evaluate CIN risk.
- Thyroid function tests if prior thyroid disease or high dose administered.
Clinical Pearls
- Pre‑hydration strategy: 0.9% saline, 200 mL / kg over 24 h *before* contrast in patients with eGFR < 60 mL/min/1.73 m² significantly lowers CIN incidence.
- Contrast volume calculation: Ideal body weight (IBW) × 1.5 mL/kg often produces less nephrotoxicity than using actual body weight; mitigate over‑dosing.
- Dilution eases tolerance: For high‑osmolar CT scans, diluting iohexol 1 : 2 with saline reduces jet irritation and improves patient comfort.
- Use a “fast‑track” contrast protocol for children: 0.3 mL/kg IV, rate 1.5 mL/s, to maintain image quality while limiting volume.
- Keep a record of prior contrast reactions: Even mild, non‑anaphylactic reactions predict higher likelihood of severe hypersensitivity in future administrations.
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• Key Takeaway: Omnipaque 350 is a safe, widely used iodinated contrast agent when administered with appropriate renal protection strategies. Proper dosing, hydration, and monitoring are essential for optimal outcomes and minimal adverse events.