Iohexol
**Iohexol** is a non-ionic, low-osmolar contrast medium (LOCM) widely used in veterinary medicine for radiographic imaging and as a precise marker for estimating **glomerular filtration rate (GFR)**. * **Imaging**: Provides excellent radiopacity for myelography, excretory urography, angiography, and gastrointestinal studies. * **Safety Profile**: Compared to older high-osmolar ionic contrast agents (e.g., diatrizoate), iohexol has significantly lower osmolality. This results in fewer adverse hemodynamic effects, less endothelial and erythrocyte damage, and reduced pain or heat sensation upon injection. * **Renal Function Testing**: Because it is freely filtered by the kidneys without being secreted or reabsorbed, its clearance closely mimics inulin. It is highly stable in plasma and urine, making it an ideal, practical, and cost-effective marker for detecting early kidney disease when standard markers (BUN, creatinine) are insufficiently sensitive.
กลไกการออกฤทธิ์: * **Radiographic Contrast**: Iohexol contains **organic iodine** atoms that absorb X-rays via the **photoelectric effect** → increases the radiopacity of the fluid or structure it fills → allows clear delineation of adjacent tissues on radiographs or CT scans. * **GFR Marker**: Iohexol has negligible protein binding (<1%) and is freely filtered by the **glomerulus** → it is neither secreted nor reabsorbed by the renal tubules → nearly 100% is excreted unchanged in the urine within 24 hours. By measuring the rate of plasma disappearance over time, clinicians can accurately calculate the **glomerular filtration rate (GFR)**.
ขนาดยาตามชนิดสัตว์
- Estimate GFR (single sample method) · 90 mg iodine content/kg in non-azotemic animals and 45 mg iodine content/kg in azotemic animals · IV · Single dose · Samples drawn at 120 min to assess validity of single-sample method.
- Contrast agent for suspected GI perforation · 1:3 dilution of iohexol 240 at 10 mL/kg of body weight · PO · Single dose · Best administered via nasogastric/nasoesophageal tube.
- Contrast agent (GI abnormalities, transit time) · estimated crop volume of 25-30 mL/kg. Iohexol may be diluted 1:1 with water · PO · Single dose · Administered directly into the crop by gavage. Retrograde administration directly into the cloaca may help evaluate cloacal abnormalities. Preferred over barium if perforation is suspected.
- Estimate GFR (2-4 sample method) · 129-658 mg/kg · IV · Single dose · Given over a minute. Lower doses may result in plasma concentrations too low for accurate analysis.
- Estimate GFR (single sample method) · 90 mg iodine content/kg in non-azotemic animals and 45 mg iodine content/kg in azotemic animals · IV · Single dose · Samples drawn at 120 min to assess validity of single-sample method.
- Contrast agent for suspected GI perforation · 700-875 mg Iodine/kg, 10 mL/kg · PO · Single dose · Best administered via orogastric tube. Radiographs obtained immediately, then at 15, 30, and 60 minutes.
ขนาดยาเป็นข้อมูลอ้างอิงทางคลินิกสำหรับสัตวแพทย์ผู้มีใบอนุญาต โปรดตรวจสอบกับฉลากล่าสุดและผู้ป่วยแต่ละรายเสมอ
วิธีการให้ยา
ข้อห้ามใช้
- Prior hypersensitivity reaction to iohexol or iodine-containing products
อาการไม่พึงประสงค์
- Hypersensitivity reactions (rare)
- Nephrotoxicity (slight risk)
- Pain or heat sensation at injection site (less common than with ionic agents)
อันตรกิริยาระหว่างยา
- Drugs that prolong QTc interval (e.g., amiodarone, cisapride, procainamide, quinidine, sotalol, dolasetron, moxifloxacin) · May cause additive prolongation of the QTc interval, though iohexol causes less prolongation than diatrizoate.
- Iodine Isotopes · May alter binding to thyroid tissue for up to two weeks, affecting certain thyroid treatments or scans.
- Phenothiazines · May increase the risk for lowering the seizure threshold, especially when iohexol is used intrathecally.
การติดตาม
- Signs of hypersensitivity or anaphylaxis during and immediately after administration
- Renal function (if pre-existing impairment exists)
- Hydration status
การได้รับยาเกินขนาด
Adverse effects of intravenous overdosage can be serious and life-threatening, primarily affecting the **pulmonary** and **cardiovascular systems**. * **Clinical Signs**: Cyanosis, bradycardia, acidosis, pulmonary hemorrhage, convulsions, coma, and cardiac arrest. * **Treatment**: Treatment is entirely supportive and symptomatic. Maintain airway, support ventilation, and manage cardiovascular collapse with appropriate fluids and vasopressors as needed.
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