イオヘキソール
**イオヘキソール (Iohexol)** は、獣医療においてX線画像診断や**糸球体濾過量 (GFR)** を評価するための精密なマーカーとして広く使用されている非イオン性低浸透圧造影剤 (LOCM) です。 * **画像診断**：脊髄造影、排泄性尿路造影、血管造影、および消化管検査において優れたX線不透過性を提供します。 * **安全性**：古い高浸透圧イオン性造影剤（ジアトリゾ酸など）と比較して、イオヘキソールは浸透圧が著しく低いです。これにより、血行動態への悪影響が少なく、内皮細胞や赤血球への損傷が軽減され、注射時の痛みや熱感が減少します。 * **腎機能検査**：腎臓で自由に濾過され、分泌や再吸収を受けないため、そのクリアランスはイヌリンに非常に似ています。血漿および尿中で非常に安定しており、標準的なマーカー（BUN、クレアチニン）の感度が不十分な場合に、早期の腎疾患を検出するための理想的で実用的かつ費用対効果の高いマーカーです。
作用機序: * **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)**.
動物種別の用量
- 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.
用量は獣医療従事者向けの臨床リファレンスです。必ず最新の添付文書と個々の患者で確認してください。
投与経路
禁忌
- Prior hypersensitivity reaction to iohexol or iodine-containing products
有害事象
- Hypersensitivity reactions (rare)
- Nephrotoxicity (slight risk)
- Pain or heat sensation at injection site (less common than with ionic agents)
薬物相互作用
- 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.
モニタリング
- Signs of hypersensitivity or anaphylaxis during and immediately after administration
- Renal function (if pre-existing impairment exists)
- Hydration status
過量投与
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.
VetSheet の薬剤リファレンスは、獣医療従事者向けの臨床意思決定支援を目的としており、専門的判断やメーカーの最新添付文書に代わるものではありません。