バソプレシン
**バソプレシン**（抗利尿ホルモン、ADHとも呼ばれる）は、視床下部で合成され下垂体後葉に貯蔵される内在性ペプチドホルモンです。獣医療においては以下の重要な役割を果たします： * **診断薬**：主に水制限試験において、中枢性尿崩症と腎性尿崩症を鑑別するために使用されます。 * **救急・集中治療**：血管拡張性ショックの補助治療や、心肺脳蘇生（CPCR）時の使用が増加しています。 > **臨床のポイント**：重度のショックや心停止（心室静止/無脈性電気活動）の状態において、バソプレシンはエピネフリンよりも明確な利点を提供します。アシドーシス環境下でも強力な血管収縮を引き起こし、冠状動脈および腎血管を保護（心筋灌流を改善）し、カテコールアミンに関連する催不整脈作用や変時作用を持ちません。 歴史的には中枢性尿崩症の治療に使用されていましたが、長時間作用型の油性製剤が製造中止となったため、現在では長期管理には合成アナログである**デスモプレシン（DDAVP）**が主に代用されています。
作用機序: Vasopressin exerts its effects via multiple receptor subtypes: * **V1 Receptors (Vascular Smooth Muscle)**: Mediates profound vasoconstriction. At high doses, it causes contraction of capillaries and small arterioles, increasing systemic vascular resistance and blood pressure. It also stimulates smooth muscle in the bladder, gallbladder, and GI tract. * **V2 Receptors (Renal Collecting Ducts)**: Mediates antidiuretic effects. Vasopressin binds to V2 receptors → activates adenylate cyclase → increases **cAMP** → promotes the insertion of **aquaporin-2 channels** into the luminal membrane → increases water permeability and reabsorption of solute-free water → concentrates urine and decreases urine flow. * **V3 Receptors (Pituitary)**: Stimulates the release of corticotropin (ACTH). * **Oxytocin & Purinergic (P2) Receptors**: Minimal oxytocic effects at standard doses, but massive doses can stimulate uterine contraction.
動物種別の用量
- Diagnostic agent (after water deprivation test) · 0.5 U/kg IM · IM · Once · Empty bladder and determine specific gravity at 30, 60, and 120 minutes after administration.
- Adjunctive treatment of vasodilatory shock (unresponsive to fluids/catecholamines) · 0.01-0.04 Units/minute IV · IV · CRI
- CPCR (pulseless electrical activity or ventricular asystole) · 0.2-0.8 Units/kg, IV once · IV · Once · May be beneficial for myocardial and cerebral blood flow.
- Diagnostic agent (Exogenous vasopressin test after water deprivation test) · 2.5 mU/kg IV over one hour · IV · Once · 1 hour · Give aqueous vasopressin in D5W. Empty bladder and collect urine at 30, 60, and 90 minutes.
- Adjunctive treatment of vasodilatory shock (unresponsive to fluids/catecholamines) · 0.01-0.04 Units/minute IV · IV · CRI · Dose is not dependent upon patient weight. DO NOT exceed 0.04 Units/minute (risk of myocardial ischemia). DO NOT use in cardiogenic shock.
- CPCR (pulseless electrical activity or ventricular asystole) · 0.2-0.8 Units/kg, IV once · IV · Once · May be beneficial for myocardial and cerebral blood flow.
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 to vasopressin
- Chronic nephritis until nitrogen retention is resolved to reasonable levels
- Cardiogenic shock (due to risk of myocardial ischemia)
有害事象
- Local irritation at the injection site
- Sterile abscesses
- Skin reactions
- Platelet aggregation
- Bilirubinemia
- Abdominal pain
- Hematuria
- Hypersensitivity (urticarial) reactions
- Water intoxication (with overdosage)
薬物相互作用
- Alcohol · May inhibit the antidiuretic activity of vasopressin
- Demeclocycline · May inhibit the antidiuretic activity of vasopressin
- Epinephrine (large doses) · May inhibit the antidiuretic activity of vasopressin
- Heparin · May inhibit the antidiuretic activity of vasopressin
- Norepinephrine (large doses) · May inhibit the antidiuretic activity of vasopressin
- Antidepressants, Tricyclic · May potentiate the antidiuretic effects of vasopressin
- Carbamazepine · May potentiate the antidiuretic effects of vasopressin
- Chlorpropamide · May potentiate the antidiuretic effects of vasopressin
- Clofibrate · May potentiate the antidiuretic effects of vasopressin
- Fludrocortisone · May potentiate the antidiuretic effects of vasopressin
- Phenformin · May potentiate the antidiuretic effects of vasopressin
- Urea · May potentiate the antidiuretic effects of vasopressin
モニタリング
- Urine output and frequency
- Water consumption
- Urine specific gravity
- Urine osmolality
- Blood pressure and ECG (when used for shock/CPCR)
過量投与
### Water Intoxication Overdosage of vasopressin leads to excessive water retention and subsequent **water intoxication** (dilutional hyponatremia). * **Early Signs**: Listlessness, depression, and lethargy. * **Severe Signs**: Coma, seizures, and eventually death due to cerebral edema. **Treatment**: * *Mild Intoxication*: Discontinue vasopressin therapy and strictly restrict water access until clinical signs resolve. * *Severe Intoxication*: May require the administration of osmotic diuretics (e.g., mannitol, urea, or dextrose) with or without a loop diuretic like furosemide to rapidly excrete excess free water.
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。