肝素 (未分級)
肝素是一種未分級的注射型抗凝血劑，在獸醫學中用於預防和治療血栓栓塞性疾病，並維持靜脈導管的通暢。它依賴內源性抗凝血酶 III (AT III) 的存在來發揮作用。 > **臨床警告：** 肝素具有顯著的出血風險。它不能溶解現有的血栓，但能防止其擴大。 **臨床提示：** 由於肝素需要 AT III 才能發揮作用，因此在患有嚴重蛋白質流失性腎病或腸病（AT III 耗竭）的病患中可能無效。
作用機制: Heparin exerts its effects primarily by enhancing the binding of **antithrombin III (AT III)** to **factors IIa, IXa, Xa, XIa and XlIa**. * **AT III/clotting factor complex** formation → subsequent removal by the liver. * Inactivates **thrombin** → blocks the conversion of **fibrinogen** to **fibrin**. * Inhibition of **Factor XII** activation → prevents the formation of stable fibrin clots. > **Note:** Heparin is only effective if adequate AT III is present. It does not significantly change the concentrations of clotting factors, nor does it lyse pre-existing clots.
給藥途徑
禁忌症
- Active bleeding or severe bleeding disorders
- Severe thrombocytopenia
- Recent neurosurgery or ocular surgery
- Known hypersensitivity to heparin
不良反應
- Hemorrhage (most common)
- Heparin-induced thrombocytopenia (HIT)
- Injection site reactions (hematoma, pain)
- Hypersensitivity reactions
藥物相互作用
- Aspirin · Increased risk of bleeding due to platelet inhibition · major
- NSAIDs · Increased risk of gastrointestinal ulceration and bleeding · major
- Warfarin · Synergistic anticoagulant effect; increased bleeding risk · major
- Clopidogrel · Increased risk of bleeding · major
監測
- aPTT (Activated Partial Thromboplastin Time) - typically target 1.5 to 2.5 times baseline
- Platelet count
- Packed Cell Volume (PCV) and Total Protein (TP)
- Clinical signs of bleeding (mucous membranes, feces, urine)
過量
The primary sign of overdosage is **hemorrhage** (e.g., epistaxis, hematuria, melena, petechiae). * **Mild to moderate overdose:** Discontinue heparin therapy; due to its short half-life, coagulation parameters often normalize quickly. * **Severe, life-threatening hemorrhage:** Administer **protamine sulfate** as a specific reversal agent (antidote). Administer slowly IV to avoid hypotension and anaphylactoid reactions.
VetSheet 藥物參考供持牌獸醫專業人員作臨床決策輔助之用,不能取代專業判斷或廠方最新藥品說明書。