Generic Name

Iopamidol

Mechanism

Iopamidol is a *non‑ionic, low‑osmolar iodinated contrast medium*.
• Provides radiopacity by increasing the overall X‑ray attenuation of vascular or organ structures.
• Its symmetrical iodine arrangement and high iodine density (~325 mg I/mL) yield excellent vessel delineation while minimizing osmotic load on the kidneys.
• Because it is non‑ionic, it produces fewer fluid shifts and a lower risk of hyperosmolarity‑related side‑effects compared with older ionic agents.

Pharmacokinetics

• Absorption: Rapid systemic absorption when administered intravenously (IV).
• Distribution: Widely distributed in extracellular fluid; minimal protein binding (~10 %).
• Metabolism: Not metabolized; remains structurally unchanged.
• Excretion: Primarily renal via glomerular filtration; ~99 % excreted unchanged within 24 h.
• Half‑life: ~2 h in patients with normal renal function; prolonged in renal impairment.
• Drug interactions: None significant; no CYP enzyme involvement.

Indications

• Computed Tomography (CT) angiography and non‑contrast studies (CT chest, abdomen, pelvis).
• Angiography for diagnostic evaluation of vascular diseases (cerebral, coronary, peripheral).
• Extravascular imaging (e.g., contrast‑enhanced ultrasound, intravascular ultrasound).
• Barium‑contrast studies as a substitute when barium is contraindicated.

Contraindications

• Known hypersensitivity to iodinated contrast media or any component of the formulation.
• Severe renal impairment (eGFR < 30 mL/min/1.73 m²) – consider alternative imaging or pre‑hydration protocols.
• Pregnancy – use only when benefits outweigh risks, preferably with the lowest effective dose.
• History of asthma or recent upper‑respiratory infections – monitor for bronchospasm.

*Warning:* Though non‑ionic, Iopamidol can still trigger contrast‑medium–related reactions (CMRs). Pre‑medication protocols (corticosteroids, antihistamines) may be required in high‑risk patients.

Dosing

• Adults (IV):
• Standard dose: 1 – 1.5 mL/kg (max 120 mL), diluted 1:1 with normal saline in a 1‑min bolus.
• Low‑contrast procedures (e.g., CT lung): 25–30 mL.
• Adults (Intra‑arterial): 50–100 mL per run, flow‑controlled to reduce vascular irritation.
• Pediatric: Weight‑based dosing (1 mL/kg) up to a maximum of 100 mL.
• Administration method: Rapid IV push or arterial injection; avoid intra‑arterial injection below 2.5 mL/s to prevent arterial damage.
• Dilution: 1:1 (contrast: saline) for IV; 1:5 for intra‑arterial to reduce osmolarity.

Adverse Effects

• Common:
• Injection site pain, warmth, fainting.
• Mild flushing or itching.
• Serious (rare):
• Hypotension, arrhythmia, anaphylactoid reaction (urticaria, bronchospasm).
• Contrast‑induced nephropathy (CIN) – risk ↑ with baseline renal dysfunction.
• Thyrotoxicosis or thyroid dysfunction in susceptible patients.

Monitoring

• Renal function: Serum creatinine / eGFR 24 h before and 48–72 h after high‑dose studies.
• Blood pressure and heart rate: Pre‑ and post‑contrast, especially in patients with cardiac history.
• Allergy signs: Observe for >30 min post‑injection; be ready with epinephrine.
• Thyroid function tests (TFTs): In patients with pre‑existing thyroid disease or elevated baseline T4/T3.

Clinical Pearls

• Pre‑hydration is key: A simple 0.9 % saline bolus (10 mL/kg) 1 h before administration reduces CIN risk by ~30 %.
• Smaller volumes, same image quality: With advances in scanner technology, 20–30 mL of Iopamidol can often replace 100–120 mL of older agents for many CT protocols.
• Iopamidol’s iso‑osmolar buffer (≈290 mOsm/kg) means it’s gentler on the kidneys than older high‑osmolar agents; still, monitor eGFR closely in CKD patients.
• Allergy grading for pre‑medication:
• Grade I–II (mild) – oral antihistamine only.
• Grade III–IV (severe) – IV steroids + antihistamine; consider epinephrine pump if anaphylaxis risk is high.
• Use in pregnancy: Iopamidol is classified as category C; however, because it is non‑ionic and has a low protein binding fraction, it is often the agent of choice when contrast imaging is essential.

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• *Prepared by a precision pharmacology assistant. For full prescribing guidelines, always consult local protocols and the latest FDA/EMA product monograph.*