苯磺酸氨氯地平 (Amlodipine)
Amlodipine 是一種**二氫吡啶類鈣離子通道阻斷劑 (CCB)**，在獸醫學中主要用作強效的**周邊動脈血管擴張劑**。 - **貓科醫學**：它是治療**貓全身性高血壓**（通常繼發於慢性腎病、甲狀腺機能亢進或肥厚型心肌病）的**黃金標準**和第一線藥物。單獨使用於貓咪通常具有極佳療效。 - **犬科醫學**：在狗中，它通常用作難治性充血性心衰竭 (CHF) 的輔助降低後負荷藥物，或作為第二線抗高血壓藥物。在狗單獨使用較高劑量時，可能會活化腎素-血管收縮素-醛固酮系統 (RAAS)，因此經常與 ACE 抑制劑（如 enalapril）合併使用以減輕此效應。 - **臨床要點**：其作用起效相對緩慢，有助於防止急性低血壓危機，但漏服藥物可能導致血壓迅速反彈。
作用機制: Amlodipine selectively inhibits the transmembrane influx of calcium ions into vascular smooth muscle and cardiac muscle by blocking **L-type voltage-gated calcium channels**. - **Vascular Smooth Muscle** → Relaxation and vasodilation → Significant reduction in **peripheral vascular resistance (afterload)** → Decreased systemic blood pressure. - It has a much higher affinity for vascular smooth muscle than cardiac muscle, meaning it produces profound vasodilation with minimal negative inotropic (contractility) or chronotropic (heart rate) effects at therapeutic doses. - **Cardiac Muscle** → Mildly depresses impulse formation (automaticity) and conduction velocity.
各物種劑量
- Adjunctive therapy for refractory heart failure (advanced mitral valve degeneration as an afterload reducer) · 0.2-0.4 mg/kg PO twice daily. Initiate therapy at 0.1 mg/kg PO twice daily and up-titrate weekly while monitoring blood pressure. · PO · q12h · After ACE inhibitor maintenance therapy has been established.
- Arterial vasodilator for refractory CHF secondary to mitral regurgitation · 0.1 mg/kg q12-24h initially; titrate up as needed to 0.25 mg/kg PO q12-24h · PO · q12-24h · Monitor blood pressure.
- Systemic hypertension in dogs with chronic renal disease · 0.1-0.5 mg/kg PO once daily (q24h) · PO · q24h · Most often combined with an ACE inhibitor. May require weeks to months to achieve satisfactory control.
- Systemic hypertension (2nd step drug) · 0.1 mg/kg q24h; step up to 0.2 mg/kg q24h if needed · PO · q24h · Used after enalapril/benazepril. Each step added if after 1-2 weeks systolic BP > 160 mmHg.
- Systemic hypertension · 0.05-0.1 mg/kg (titrate upwards weekly as required, up to 0.5 mg/kg) · PO · q12-24h · Long-term · Monitor blood pressure regularly. Consider concurrent ACE inhibitor.
- Systemic hypertension (1st step drug) · 0.625 mg per cat q24h, if cat greater then 6 kg, 1.25 mg/cat q24h · PO · q24h · Add ACE inhibitor if proteinuric.
- Systemic hypertension · 0.625-1.25 mg (total dose) PO once daily · PO · q24h · Drug of choice; often successful as a single agent. Maximum effect seen within 7 days.
- Systemic hypertension · 0.625-1.25 mg/cat · PO · q24h (may increase slowly or increase frequency to q12h if necessary) · Long-term · Blood pressure monitoring is essential. Appears safe even with concurrent renal failure.
給藥途徑
禁忌症
- Patients with cardiogenic shock
- Advanced aortic stenosis (relative contraindication)
- Use with caution in patients with heart failure (due to slight negative inotropic effects)
- Use with caution in patients with hepatic dysfunction
不良反應
- Cats: Infrequent azotemia, lethargy, hypokalemia, reflex tachycardia, weight loss
- Dogs: Gingival hyperplasia (with long-term use)
- Anorexia and hypotension (early in therapy)
藥物相互作用
- Diuretics · Concomitant use may cause additive hypotension. · moderate
- Beta-blockers · Concomitant use may cause additive hypotension. · moderate
- Vasodilators · Concomitant use may cause additive hypotension.
- Fentanyl · May cause hypotension if used concurrently.
- Grapefruit juice/powder · May alter bioavailability of amlodipine.
- Cimetidine · May impair hepatic metabolism of amlodipine, increasing circulating levels · moderate
- Cyclosporine · May impair hepatic metabolism of amlodipine, increasing circulating levels · moderate
- Ketoconazole · May impair hepatic metabolism of amlodipine, increasing circulating levels · moderate
- Itraconazole · May impair hepatic metabolism of amlodipine, increasing circulating levels · moderate
- Rifampin · CYP3A4 inducer; may reduce circulating amlodipine levels · moderate
- ACE inhibitors · Increased risk of hypotension when combined · moderate
監測
- Systemic blood pressure (frequent monitoring during dose titration)
- Ophthalmic exam (to assess for hypertensive retinopathy/retinal detachment)
- Renal values and electrolytes (especially if combined with ACE inhibitors)
- Clinical signs of hypotension (lethargy, weakness)
過量
Overdoses pose a significant risk for **profound hypotension** and **reflex tachycardia** (though bradycardia is also possible). Common clinical signs in dogs and cats include lethargy and vomiting. **Treatment**: - When possible, massive overdoses should be managed with gut emptying (emesis/lavage) and activated charcoal. - Provide aggressive supportive treatment (IV fluids). - **Specific therapies** may include beta-agonists, intravenous lipid emulsion (ILE) therapy, and intravenous calcium to counteract the calcium channel blockade.
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