匹莫苯丹
匹莫苯丹是一種高效的心血管藥物，被歸類為**強心血管擴張劑 (Inodilator)**，這意味著它同時具有正性肌力（增加心臟收縮力）和血管擴張的特性。 **主要臨床用途：** * **犬：** 主要用於治療繼發於**擴張性心肌病 (DCM)** 或**黏液瘤性/退行性二尖瓣疾病 (MMVD)** 的鬱血性心衰竭 (CHF)。與傳統的 ACE 抑制劑/呋塞米療法相比，它能顯著提高存活時間和生活品質。它被認為是杜賓犬 DCM 的第一線療法，也是 ACVIM C 期和 D 期心衰竭管理的基石。 * **貓：** 標示外用於限制性和擴張性心肌病。由於其正性肌力作用，通常禁忌用於肥厚性心肌病 (HCM)。 > **臨床要點：** 雖然專論提到臨床前使用的研究仍在進行中，但具有里程碑意義的 EPIC 研究已經確立匹莫苯丹作為延緩患有臨床前（ACVIM B2 期）MMVD 犬隻心衰竭發作的標準護理。
作用機制: Pimobendan exerts its dual **inodilator** effects through two distinct mechanisms: 1. **Positive Inotropy (Calcium Sensitization):** It increases the sensitivity of the cardiac myofilament **Troponin C** to intracellular calcium → enhances cardiac contractility. Unlike older inotropes (e.g., digoxin), it achieves this *without* increasing intracellular calcium levels → **no increase in myocardial oxygen consumption**. 2. **Vasodilation (PDE-III Inhibition):** It inhibits the enzyme **phosphodiesterase III (PDE-III)** in vascular smooth muscle → prevents the breakdown of cAMP → ↑ intracellular cAMP → smooth muscle relaxation → **mixed arterial and venous dilation**. This reduces both cardiac preload and afterload. Additionally, pimobendan possesses mild antithrombotic activity.
各物種劑量
- Management of myocardial failure (DCM), especially if not associated with taurine deficiency · 1.25-1.5 mg/cat PO q12hrs · PO · q12h · Off-label use. Little information about clinical efficacy due to rarity of condition.
- Heart failure associated with systolic dysfunction (Off-label) · 0.1-0.3 mg/kg · PO · q12h · Lifelong · Not authorized (off-label). Pharmacokinetics may differ from dogs. Administer 1 hour before food.
- Management of the signs of mild, moderate or severe congestive heart failure due to AV valve insufficiency or dilated cardiomyopathy · 0.5 mg/kg total daily dose. Divide daily dose into two portions that are not necessarily equal (using whole and half tablets) and administer approximately 12 hours apart. · PO · Divided q12h
- Treatment of congestive heart failure secondary to myxomatous mitral valve disease (MMVD) · 0.4-0.6 mg/kg PO divided twice daily · PO · Divided twice daily
- Treatment of heart failure secondary to dilated cardiomyopathy or chronic mitral valve insufficiency · 0.25 mg/kg PO twice daily · PO · Twice daily
- General dosing · 0.2-0.6 mg/kg PO divided q12h · PO · Divided q12h
- Adjunctive drug for the emergency treatment of CHF (if not overtly critical and a strong positive oral inotrope is needed) · 0.1-0.3 mg/kg PO q12h · PO · q12h
- Adjunctive treatment of acute or chronic stage D heart failure (refractory to standard treatment) · 0.3 mg/kg PO to three times daily · PO · Up to TID · Outside of FDA-approved labeling; requires client consent.
給藥途徑
禁忌症
- Hypersensitivity to pimobendan
- Hypertrophic cardiomyopathy (HCM)
- Aortic stenosis
- Any condition where augmentation of cardiac output is inappropriate for functional or anatomic reasons
- Any condition where augmentation of cardiac output via increased contractility is not possible anatomically or functionally
不良反應
- Poor appetite
- Lethargy
- Diarrhea
- Dyspnea
- Azotemia
- Weakness and ataxia
- Pleural effusion
- Syncope
- Cough
- Ascites
- Heart murmur
- Arrhythmias (atrial fibrillation, increased ventricular ectopic beats)
- Worsening mitral valve lesions (acute hemorrhages, endocardial papilloform hyperplasia) with chronic use
- Moderate positive chronotropic effect (tachycardia)
- Vomiting (dose-dependent)
- Reduced appetite or lethargy (rare)
藥物相互作用
- Verapamil · Calcium antagonist; attenuates pimobendan-induced increases in cardiac contractility.
- Propranolol · Beta-antagonist; attenuates pimobendan-induced increases in cardiac contractility.
- Diltiazem · Calcium channel blocker; assumed to potentially attenuate positive inotropic effects.
- Atenolol · Beta-blocker; assumed to potentially attenuate positive inotropic effects.
- Beta-blockers (e.g., atenolol, propranolol) · Attenuates the positive inotropic effects of pimobendan · moderate
- Calcium-channel blockers (e.g., verapamil, diltiazem) · Attenuates the positive inotropic effects of pimobendan · moderate
監測
- ECG (rate and rhythm)
- Blood pressure
- Echocardiography (cardiac function and valve lesions)
- Clinical signs of heart failure (coughing, exercise intolerance)
- Resting respiratory rate (RRR) at home
- Heart rate and rhythm
- Respiratory rate and effort (Resting Respiratory Rate - RRR)
- Echocardiographic parameters (fractional shortening, left atrial/ventricular dimensions)
- Clinical signs of congestive heart failure
過量
Overdoses primarily manifest as cardiovascular signs. **Clinical Signs:** * Tachycardia (dose-dependent increases in heart rate) * Mild, non-clinical heart murmurs * Hypotension **Treatment:** * **Decontamination:** Induce emesis and administer activated charcoal if exposure was recent. * **Monitoring:** Continuously monitor heart rate, blood pressure, and ECG. * **Supportive Care:** Control hypotension with IV fluids and dopamine if necessary.
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