カプトプリル
カプトプリルは、スルフヒドリル基を持つ第一世代の**アンジオテンシン変換酵素（ACE）阻害薬**です。元々は南米のクサリヘビの毒から分離されたペプチドに由来し、最初のACE阻害薬として歴史的に重要な意味を持ちます。 うっ血性心不全（CHF）や高血圧の治療における血管拡張薬として有効ですが、半減期が短く（多くの場合1日3回の投与が必要）、副作用（特に犬における消化器症状）の発生率が高いため、現在獣医療では**エナラプリル**や**ベナゼプリル**などの新しい薬剤にほぼ取って代わられています。 **臨床のポイント：**エナラプリルとは異なり、カプトプリルはそれ自体が活性薬物であり、効果を発揮するために肝臓で活性代謝物に変換される必要はありません。
作用機序: Captopril acts as a competitive inhibitor of **angiotensin-converting enzyme (ACE)**, for which it has a much higher affinity than the natural substrate, angiotensin-I. * **Angiotensin I** → (blocked by ACE) → **Angiotensin II** (a potent vasoconstrictor). * The reduction in Angiotensin II leads to **vasodilation**, decreasing total peripheral resistance, pulmonary vascular resistance, and blood pressure. * Decreased Angiotensin II also reduces **aldosterone** secretion, leading to decreased sodium and water retention, while increasing plasma renin activity. * Cardiovascular benefits in CHF include increased cardiac output, stroke volume, and exercise tolerance with little to no change in heart rate.
動物種別の用量
- CHF / Hypertension · 1/4 to 1/2 of a 12.5 mg tablet PO q8-12h · PO · q8-12h
- Dilative, restrictive or hypertrophic cardiomyopathy · 0.55-1.54 mg/kg PO q8-12h · PO · q8-12h
- CHF / Hypertension · 0.5-2 mg/kg PO three times daily · PO · TID
- CHF / Hypertension · 0.5-2 mg/kg PO q8-12h · PO · q8-12h
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
- Hypersensitivity to ACE inhibitors
有害事象
- Hypotension
- Renal failure
- Hyperkalemia
- Vomiting
- Diarrhea
- Skin rashes (reported in humans, not dogs)
- Neutropenia/agranulocytosis (rare, reported in humans)
薬物相互作用
- Antacids · Reduced oral absorption of captopril; separate dosing by at least two hours.
- Cimetidine · Concomitant use has caused neurologic dysfunction in human patients.
- Digoxin · Digoxin levels may increase 15-30%; monitor serum digoxin levels.
- Diuretics · Concomitant use may cause hypotension; titrate dosages carefully.
- NSAIDs · May reduce the clinical efficacy of captopril when used as an antihypertensive agent.
- Potassium or Potassium-Sparing Diuretics (e.g., spironolactone) · Increased risk of developing hyperkalemia.
- Probenecid · Can decrease renal excretion of captopril, possibly enhancing clinical and toxic effects.
- Vasodilators (e.g., prazosin, hydralazine, nitrates) · Concomitant use may cause additive hypotension; titrate dosages carefully.
モニタリング
- Clinical signs of CHF (respiratory rate/effort, exercise tolerance)
- Blood pressure (especially if treating hypertension or if signs of hypotension arise)
- Serum electrolytes (monitor for hyperkalemia)
- Renal panel (Creatinine, BUN)
- Urine protein
- CBC with differential (periodic)
過量投与
The primary concern in an overdose situation is **hypotension**. * **Treatment:** Supportive treatment with volume expansion using normal saline is recommended to correct blood pressure. * **Toxicity thresholds:** Dogs given 1.5 g/kg orally developed emesis and decreased blood pressure. Dogs receiving doses greater than 6.6 mg/kg q8h may develop renal failure.
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。