硫酸魚精蛋白
**硫酸魚精蛋白 (Protamine sulfate)** 是一種簡單、低分子量的陽離子蛋白質，最初提取自鮭魚及相關魚類的精子或成熟睪丸。在獸醫學中，它主要作為**肝素 (Heparin) 過量**導致嚴重、無法控制的出血時的特效解毒劑。 主要臨床重點： * **未分段肝素 vs. 低分子量肝素 (LMWH)：** 雖然魚精蛋白能完全中和未分段肝素，但它只能*部分*中和低分子量肝素（如 dalteparin 或 enoxaparin）的抗 Xa 活性。然而，它仍能改善 LMWH 過量引起的微血管出血。 * **其他用途：** 曾被建議作為反芻動物蕨類植物 (*Pteridium spp.*) 中毒的輔助治療。 > **臨床提示：** 由於魚精蛋白是一種外來蛋白質，可能會引起過敏反應（包括過敏性休克），特別是在曾有暴露史或對魚類過敏的病患中。
作用機制: Protamine works via direct **acid-base neutralization**. * **Mechanism:** Heparin is a strongly acidic molecule, while protamine is strongly basic. * **Pathway:** Protamine → binds directly to circulating heparin → forms an inactive, stable salt complex → neutralizes heparin's anticoagulant activity. > **Pharmacology Note:** Protamine possesses weak intrinsic anticoagulant activity of its own. If administered in large doses without heparin present, it can theoretically interfere with coagulation, though this rarely causes clinical hemorrhage.
各物種劑量
- Heparin overdosage · 1-1.5 mg protamine sulfate to antagonize each mg (100 units) of heparin via slow IV injection. Reduce dose as time increases between heparin dose and start of treatment (after 30 minutes give only 0.5 mg). · IV · Single dose · Give slowly.
- Heparin overdosage · Administer 1 mg protamine for each 100 Units of heparin to be inactivated. Decrease protamine dose by ½ for every 30 minutes that have lapsed since heparin was administered · IV · Single dose · May be ineffective if heparin was given deep SC. Do not give faster than 50 mg over 10 minutes.
- Bracken Fern (Pteridium spp.) poisoning · 1 injection of 10 mL of 1% protamine sulfate IV · IV · Single dose · In combination with whole blood (2.25-4.5 L)
- Heparin overdosage · 1-1.5 mg protamine sulfate to antagonize each mg (100 units) of heparin via slow IV injection. Reduce dose as time increases between heparin dose and start of treatment (after 30 minutes give only 0.5 mg). · IV · Single dose · Give slowly.
- Heparin overdosage · Administer 1 mg protamine for each 100 Units of heparin to be inactivated. Decrease protamine dose by ½ for every 30 minutes that have lapsed since heparin was administered · IV · Single dose · May be ineffective if heparin was given deep SC. Do not give faster than 50 mg over 10 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
- Known hypersensitivity or intolerance to protamine
- Hypersensitivity to protamine
- Conditions where heparin has not been administered
不良反應
- Acute hypotension (if given too rapidly)
- Bradycardia
- Pulmonary hypertension
- Dyspnea
- Hypersensitivity/Anaphylaxis
- Heparin 'rebound' effect (bleeding hours after neutralization)
- Hypotension
- Anaphylactoid reactions
- Paradoxical bleeding (at high doses)
藥物相互作用
- Heparin · Forms a stable salt, causing the loss of anticoagulant activity of both compounds (therapeutic intent). · major
監測
- Coagulation parameters (e.g., aPTT, ACT) to assess heparin neutralization
- Blood pressure (monitor for hypotension during administration)
- Heart rate and rhythm (monitor for bradycardia)
- Respiratory rate and effort
- Signs of recurrent bleeding (heparin rebound effect) for several hours post-administration
- Coagulation times (aPTT, ACT)
- Heart rate
- Blood pressure
- Signs of anaphylaxis during administration
過量
Because protamine has inherent, albeit weak, anticoagulant activity, massive overdoses could theoretically result in **hemorrhage**. However, clinical data in humans suggests that significant overdoses (600-800 mg) typically result in only mild, transient effects on coagulation. The LD50 of protamine in mice is reported to be 100 mg/kg. Treatment of overdose should be supportive.
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