エナラプリル
エナラプリルは、獣医療において広く使用されている**アンジオテンシン変換酵素（ACE）阻害薬**です。前負荷と後負荷の両方を軽減するバランスの取れた血管拡張薬として作用し、犬や猫のうっ血性心不全（CHF）管理の基礎となる薬剤であり、ピモベンダンやフロセミドと併用されることがよくあります。 心血管系への応用に加え、エナラプリルはその**腎保護作用**でも高く評価されています。糸球体輸出細動脈の抵抗を低下させることで、糸球体内圧と蛋白尿を効果的に減少させるため、慢性腎臓病（CKD）や蛋白漏出性腎症（PLN）の標準的な補助治療薬となっています。 > **臨床のポイント：** エナラプリルは**プロドラッグ**であり、肝臓で生体内変換されて活性代謝物である**エナラプリラト**になる必要があります。重度の肝機能障害を持つ患者では、この変換が損なわれる可能性があり、代替療法を検討すべき場合があります。主に腎臓から排泄されるため、著しい腎機能障害を持つ患者では用量調整が必要になることがよくあります。
作用機序: Enalapril is a prodrug converted in the liver to the active compound **enalaprilat**. Enalaprilat competitively binds to and inhibits **Angiotensin-Converting Enzyme (ACE)**. * **RAAS Inhibition:** Prevents the conversion of inactive **Angiotensin-I** → active **Angiotensin-II** (a potent vasoconstrictor). * **Vasodilation:** Decreased Angiotensin-II leads to reduced total peripheral resistance, pulmonary vascular resistance, and blood pressure (↓ afterload and preload). * **Aldosterone Reduction:** Lower Angiotensin-II levels reduce the secretion of **aldosterone** from the adrenal cortex, leading to decreased sodium and water retention, while mildly increasing potassium retention. * **Renal Hemodynamics:** Preferentially dilates the **efferent arteriole** of the glomerulus. This reduces intraglomerular hydrostatic pressure, thereby decreasing the filtration of proteins into the urine (anti-proteinuric effect) and slowing the progression of glomerular disease.
動物種別の用量
- For adjunctive treatment of heart failure due to hypertrophic cardiomyopathy · 1.25-2.5 mg (total dose) PO once daily (q24h). · PO · q24h
- For adjunctive treatment of heart failure due to hypertrophic cardiomyopathy · 0.25-0.5 mg/kg (roughly 1.25-2.5 mg per cat) PO once a day (q24h) · PO · q24h
- For adjunctive treatment of heart failure due to hypertrophic cardiomyopathy · 0.5 mg/kg PO once daily, twice daily if necessary · PO · once to twice daily
- For proteinuria, hypertension in chronic kidney disease · 0.25 mg/kg PO once daily to 0.5 mg/kg PO twice daily; rarely higher · PO · once to twice daily
- For systemic hypertension · As a 2nd step drug when systolic BP >160 mmHg, diastolic >120 mmHg: 1) amlodipine (0.625 mg per cat q24h, if cat greater then 6 kg, 1.25 mg/cat q24h), add ACE inhibitor if proteinuric; 2) ACE inhibitor (benazepril/enalapril 0.5 mg/kg q12h); 3) spironolactone (1-2 mg/kg twice daily); 4) hydralazine 0.5 mg/kg PO twice daily. Each step added (except when increasing amlodipine dose) if after 1-2 weeks systolic BP > 160 mmHg. · PO · q12h · Stepwise therapy protocol.
- For adjunctive therapy for heart failure · 0.5 mg/kg PO once every other day (q48h) initially and may be increased to once a day if tolerated. · PO · q48h to q24h · Dissolve tablet(s) in distilled water and add a methylcellulose suspending agent (e.g., Ora-Plus) and cherry syrup for flavor.
- For dilative cardiomyopathy · 0.25-0.5 mg/kg PO once a day to every other day · PO · q24h to q48h
投与経路
禁忌
- Hypersensitivity to ACE inhibitors
- Pregnancy (Category C in first trimester, Category D in second/third trimesters due to fetal kidney developmental risks)
有害事象
- Anorexia
- Vomiting
- Diarrhea
- Weakness
- Hypotension
- Renal dysfunction
- Hyperkalemia
- Lethargy (especially in cats)
- Inappetence
薬物相互作用
- Antidiabetic agents (insulin, oral agents) · Possible increased risk for hypoglycemia; enhanced monitoring recommended
- Diuretics (e.g., furosemide, hydrochlorothiazide) · Potential for increased hypotensive effects; furosemide doses may need reduction (by 25-50%) when adding enalapril
- Potassium-sparing diuretics (e.g., spironolactone, triamterene) · Increased hyperkalemic effects; enhanced monitoring of serum potassium recommended
- Hypotensive agents · Potential for increased hypotensive effect
- Lithium · Increased serum lithium levels possible; increased monitoring required
- NSAIDs · May reduce the anti-hypertensive or positive hemodynamic effects of enalapril; may increase risk for reduced renal function
- Potassium supplements · Increased risk for hyperkalemia
モニタリング
- Clinical signs of CHF (respiratory rate/effort, exercise tolerance)
- Serum electrolytes (especially potassium)
- Renal panel (creatinine, BUN)
- Urine protein (UPC ratio)
- CBC with differential (periodic)
- Blood pressure (especially if treating hypertension or if clinical signs of hypotension arise)
過量投与
In dogs, a dose of 200 mg/kg was lethal, but 100 mg/kg was not. * **Primary Concern:** Severe **hypotension**. * **Treatment:** Supportive treatment with volume expansion using normal saline is recommended to correct blood pressure. * **Monitoring:** Because of the drug's long duration of action, prolonged monitoring and treatment may be required. * **Decontamination:** Recent overdoses should be managed by using gut emptying protocols when warranted.
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。