碘海醇
**碘海醇 (Iohexol)** 是一種非離子型、低滲透壓顯影劑 (LOCM)，在獸醫學中廣泛用於放射影像學檢查，並作為評估**腎絲球濾過率 (GFR)** 的精確標記物。 * **影像學檢查**：為脊髓攝影、排泄性尿路攝影、血管攝影及胃腸道檢查提供優異的放射不透明度。 * **安全性**：與早期的傳統高滲透壓離子型顯影劑（如泛影酸鹽）相比，碘海醇的滲透壓顯著較低。這使得血流動力學的不良反應減少，內皮細胞與紅血球損傷降低，並減輕注射時的疼痛或灼熱感。 * **腎功能測試**：由於它能被腎臟自由濾過，且不被分泌或再吸收，其清除率與菊糖 (inulin) 極為相似。它在血漿和尿液中高度穩定，當標準指標（BUN、肌酸酐）不夠敏感時，是檢測早期腎臟疾病的理想、實用且具成本效益的標記物。
作用機制: * **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)**.
各物種劑量
- 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.
劑量為合格獸醫專業人員的臨床參考。請務必對照最新藥品仿單及個別病患確認。
給藥途徑
禁忌症
- Prior hypersensitivity reaction to iohexol or iodine-containing products
不良反應
- Hypersensitivity reactions (rare)
- Nephrotoxicity (slight risk)
- Pain or heat sensation at injection site (less common than with ionic agents)
藥物相互作用
- 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.
監測
- Signs of hypersensitivity or anaphylaxis during and immediately after administration
- Renal function (if pre-existing impairment exists)
- Hydration status
過量
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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