プロタミン硫酸塩
**プロタミン硫酸塩**は、サケや関連魚類の精子または成熟精巣から得られる、単純で低分子量のカチオン性タンパク質です。獣医療においては、主に**ヘパリン過剰投与**による重篤な出血に対する特異的な解毒剤として使用されます。 重要な臨床ポイント： * **未分画ヘパリン vs 低分子量ヘパリン（LMWH）：** プロタミンは未分画ヘパリンを完全に中和しますが、低分子量ヘパリン（ダルテパリンやエノキサパリンなど）の抗Xa活性は*部分的に*しか中和しません。ただし、LMWH過剰による微小血管出血を改善する効果はあります。 * **その他の用途：** 反芻動物におけるワラビ（*Pteridium spp.*）中毒の補助治療として提案されています。 > **臨床のポイント：** プロタミンは異種タンパク質であるため、特に過去に投与歴がある患者や魚アレルギーのある患者では、過敏症反応（アナフィラキシーを含む）が起こる可能性があります。
作用機序: 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.
動物種別の用量
- 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.
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
- Known hypersensitivity or intolerance to protamine
- Hypersensitivity to protamine
- Conditions where heparin has not been administered
有害事象
- 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)
薬物相互作用
- Heparin · Forms a stable salt, causing the loss of anticoagulant activity of both compounds (therapeutic intent). · major
モニタリング
- 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
過量投与
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.
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。