ヘパリンナトリウム
ヘパリンナトリウムは、獣医療において主に血栓塞栓症の管理や、議論の余地はあるものの播種性血管内凝固症候群（DIC）の治療に使用される注射用**抗凝固薬**です。 主な臨床応用： - **血栓予防**：高リスク患者における大血管血栓塞栓症の発生率を低下させる強力なエビデンスがあります。 - **DICの管理**：歴史的にDICに使用されてきましたが、現在のコンセンサスでは、炎症プロセスを併発しているDIC患者への使用は推奨されていません。 - **馬の医療**：蹄葉炎の予防、DIC、および術後の腸管癒着を予防するための腹腔内洗浄に使用されます。 > **臨床のポイント**：未分画ヘパリン（UFH）は、低分子量ヘパリン（LMWH）と比較して薬物動態プロファイルが非常に不安定です。治療効果を確保し、致命的な出血を避けるために、aPTTまたは抗Xa活性の厳密なモニタリングが必要です。
作用機序: Heparin acts as an indirect anticoagulant by binding to and potentiating the activity of **Antithrombin III (ATIII)**. - **Low Concentrations**: The Heparin-ATIII complex rapidly inactivates **Factor Xa**, preventing the conversion of prothrombin to thrombin. - **High Concentrations**: The complex inactivates **Thrombin (Factor IIa)**, blocking the conversion of fibrinogen to fibrin, and also inactivates factors **IX, XI, and XII**. - **Fibrin Stabilization**: By inhibiting the activation of **Factor XIII**, heparin prevents the formation of stable fibrin clots. *Note*: Heparin does **not** lyse existing clots (it is not a thrombolytic); rather, it prevents the expansion of existing thrombi and the formation of new ones. It also increases the release of **lipoprotein lipase**, boosting the clearance of circulating lipids.
動物種別の用量
- Adjunctive treatment of DIC · 75 Units/kg SC three times daily OR 5-10 Units/kg/hour by continuous IV infusion OR 50-100 Units/kg SC q6h · SC/IV · Variable · Doses extrapolated from general small animal guidelines in monograph.
- Feline arterial thromboembolism · 250-300 Units/kg SC q8h · SC/IV · q8h · First dose is administered IV to cats showing signs of shock.
- Maintenance therapy for arterial thromboembolic disease · 250-300 Units/kg SC every 8 hours · SC · q8h · Initial in-hospital therapy
- Prevention of complications associated with hypercoagulable states · Initially 150 Units/kg SC. Then 125 Units/kg q12h for 6 doses and then decreased to 100 Units/kg SC every 12 hours. · SC · q12h
- Adjunctive treatment of DIC · 80-100 Units/kg IV q4-6h (may be added to fluids and given as a slow drip). Low grade DIC may be treated with 25-40 Units/kg SC 2-3 times a day. · IV/SC · q4-6h or 2-3x daily
- Adjunctive therapy in endotoxic shock · 40 Units/kg IV or SC 2-3 times a day · IV/SC · q8-12h · May prevent the development of microthrombi.
- Adjunctive therapy in the prevention of laminitis · 25-100 Units/kg subcutaneously 3 times daily · SC · q8h · Higher doses used when a thrombotic event is underway.
- Prevention of abdominal adhesions · 30,000-50,000 Units heparin in 10 L of lavage fluid (warm LRS) administered intraperitoneally · Intraperitoneal · At 12, 18, 36, and 48 hours post-surgery · 48 hours · Administered via a 32 french fenestrated trocar catheter.
投与経路
禁忌
- Known hypersensitivity to heparin
- Severe thrombocytopenia
- Uncontrollable bleeding (not caused by DIC)
- Intramuscular (IM) administration (causes hematomas)
- Actively bleeding DIC patients with severe factor depletion
有害事象
- Hemorrhage (most common)
- Thrombocytopenia
- Hypersensitivity reactions (derived from bovine/porcine tissue)
- Anemia in horses (due to erythrocyte agglutination)
- Injection site pain and hematoma (especially if given IM)
- Vasospastic reactions
- Osteoporosis (with long-term use)
- Rebound hyperlipidemia
- Hyperkalemia
- Alopecia
薬物相互作用
- Aspirin · May increase the risk for hemorrhage
- Dextran · May increase the risk for hemorrhage
- NSAIDs · May increase the risk for hemorrhage
- Warfarin · May increase the risk for hemorrhage
- Antihistamines · May partially counteract heparin's anticoagulant effects
- Nitroglycerin (IV) · May partially counteract heparin's anticoagulant effects
- Propylene Glycol · May partially counteract heparin's anticoagulant effects
- Digoxin · May partially counteract heparin's anticoagulant effects
- Tetracyclines · May partially counteract heparin's anticoagulant effects
モニタリング
- Activated partial thromboplastin time (aPTT) - most often recommended
- Whole blood clotting time (WBCT)
- Partial thromboplastin time (PTT)
- Activated clotting time (ACT)
- Thromboelastography (TEG)
- Platelet counts
- Packed cell volume (PCV) / Hematocrit
- Occult blood in stool and urine
- Clinical signs of bleeding or efficacy
過量投与
Overdosage of heparin is directly associated with **severe bleeding**. Clinical signs preceding frank hemorrhage include: - Hematuria - Tarry stools (melena) - Petechiae and ecchymoses (bruising) **Reversal**: **Protamine sulfate** can be administered to reverse heparin's anticoagulant effects. It binds to heparin to form a stable, inactive complex.
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