1. Clinical Overview
Diatrizoic Acid (58%) is a high-osmolality, ionic, iodinated contrast medium used for radiographic imaging. It is a tri-iodinated benzoic acid derivative containing approximately 58% organically bound iodine (approximately 290 mg I/mL). It is primarily used for intravascular administration in procedures like urography, angiography, and computed tomography (CT). Its high osmolality (approximately 1500 mOsm/kg water) compared to blood plasma is a key factor in its side effect profile, particularly nephrotoxicity and cardiovascular effects.
| Onset | Duration | Bioavailability |
|---|---|---|
| Immediate upon intravascular injection; radiographic contrast is visible within seconds. | Contrast effect typically lasts 30 to 60 minutes, depending on the vascularity and function of the target organ (e.g., renal excretion). | 100% upon intravascular administration. Not applicable for oral absorption as it is not intended for systemic effect via the GI tract. |
2. Mechanism of Action
Diatrizoic Acid provides radiographic contrast by attenuating X-rays. The three iodine atoms in its structure have a high atomic number (53), which results in high photoelectric absorption of X-ray photons. This absorption prevents X-rays from reaching the detector/film, creating a white or 'opaque' image of the vascular spaces or hollow viscera into which it is introduced.
3. Indications & Uses
- Intravenous Urography (Excretory Urography/IVP)
- Peripheral Arteriography and Venography
- Contrast-enhanced Computed Tomography (CT) of body (where cost is a major constraint)
- Hysterosalpingography
4. Dosage & Administration
Adult Dosage: Dose varies by procedure. **Examples:** IV Urography: 50-100 mL (14.5-29g iodine). Angiography: Varies by vessel, typically 20-50 mL per injection. CT: 50-150 mL. Dose must be individualized based on patient weight, procedure, and equipment.
Administration: For intravascular use only. Must be at room temperature. Inspect for particulate matter and discoloration. Administer via a secure intravenous line, preferably using an automated injector for angiography/CT. A test dose is NOT recommended as it is unreliable. Patient must be well-hydrated before and after administration.
5. Side Effects
Common side effects may include:
- Feeling of warmth/flushing (80-90%)
- Metallic taste in mouth
- Nausea, mild vomiting
- Pain at injection site
- Mild urticaria (hives)
- Sneezing
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Other Nephrotoxic Drugs (Aminoglycosides, Amphotericin B, NSAIDs, Cisplatin) | Increased risk of Contrast-Induced Nephropathy (CIN). | Major |
| Beta-blockers (especially non-selective like Propranolol) | May potentiate anaphylactoid reactions and make them harder to treat with epinephrine. | Moderate |
| Interleukin-2 | Increased risk of delayed adverse reactions. | Moderate |
| Metformin | Risk of lactic acidosis if CIN occurs. Metformin should be withheld before the procedure and resumed only after renal function is confirmed stable. | Major |
| Diuretics (especially Loop Diuretics) | May exacerbate dehydration and increase risk of CIN. | 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, including over-the-counter drugs and herbal supplements.
- DO follow pre-procedure fasting instructions if given.
- DO drink plenty of fluids before and after the procedure as advised to protect your kidneys.
- DO inform the radiologist if you are or might be pregnant.
- DONT stop or start any medication without consulting your doctor, especially metformin.
8. Toxicology & Storage
Overdose: Symptoms are an extension of side effects: Severe cardiovascular collapse, pulmonary edema, seizures, renal shutdown, and hyperosmolar coma. Death can occur from anaphylaxis or cardiac failure.
Storage: Store at room temperature (15-30°C). Protect from light and freezing. Do not use if the solution is discolored or contains particulate matter. Keep in the original package until use.