普萘洛爾
普萘洛爾是一種**非選擇性β-腎上腺素受體阻斷劑**（β-blocker），在獸醫學中主要用作**抗心律不整藥物**。它被歸類為第二類抗心律不整藥物。 * **主要用途：** 治療心房和心室心搏過速（例如 APCs、VPCs、心房顫動）、肥厚型心肌病 (HCM) 以及全身性高血壓。 * **內分泌用途：** 常用於控制**貓甲狀腺機能亢進**和嗜鉻細胞瘤中交感神經過度刺激所引起的心血管和神經肌肉症狀。 * **行為用途：** 偶爾用於標示外用途，以治療狗的情境焦慮或對巨大聲響的恐懼症。 > **臨床要點：** 由於普萘洛爾是非選擇性的，它會同時阻斷心臟和肺部的受體。對於患有貓氣喘或其他支氣管痙攣性呼吸道疾病的病患，應極度謹慎使用或避免使用。
作用機制: Propranolol acts via **competitive blockade of both $\beta_1$ and $\beta_2$ adrenergic receptors**. * **$\beta_1$ Blockade (Cardiac):** $\rightarrow$ Decreases sinus heart rate (negative chronotropy) $\rightarrow$ Depresses AV node conduction (negative dromotropy) $\rightarrow$ Decreases myocardial contractility (negative inotropy) $\rightarrow$ Ultimately reduces cardiac output and myocardial oxygen demand. * **$\beta_2$ Blockade (Pulmonary/Vascular):** $\rightarrow$ Can cause bronchoconstriction and peripheral vasoconstriction. * **Additional Effects:** Possesses **membrane-stabilizing (quinidine-like) effects** at higher doses, which alters the cardiac action potential. It lacks intrinsic sympathomimetic activity (ISA) and inhibits glycogenolysis.
各物種劑量
- Susceptible cardiac arrhythmias · 0.02 mg/kg IV slowly (up to a maximum of 1 mg/kg) · IV · As needed
- Susceptible cardiac arrhythmias · 2.5 mg (up to 10 mg) total dose per cat q 8-12h. · PO · q8-12h
- Susceptible cardiac arrhythmias · 0.02 mg/kg IV over one minute; can repeat up to a maximum of four times as needed based upon response · IV · As needed
- Adjunctive therapy in heart failure · 2.5-10 mg (total dose) PO q8h (start low and titrate) · PO · q8h
- Adjunctive therapy of hypertension · 2.5-5 mg (total dose) PO q8-12h · PO · q8-12h
- Adjunctive therapy in feline hyperthyroidism · 2 mg/kg (6.25 mg per cat) once daily · PO · q24h · To control neuromuscular and cardiovascular effects
- Hypertrophic cardiomyopathy · 0.5-2 mg/kg PO or SC once a day to twice a day · PO/SC · q12-24h
- Hypertrophic cardiomyopathy · 0.2-2 mg/kg PO q8-12h. · PO · q8-12h
- V-Tach · 0.05-0.16 mg/kg IV · IV · Single dose · Negative inotropic and chronotropic effects may be undesirable.
- V-Tach · 0.03-0.15 mg/kg IV · IV · Single dose · Considered not as effective as lidocaine; decreases ventricular rate even if it does not restore sinus rhythm. Use with caution in animals with airway disease.
給藥途徑
禁忌症
- Overt heart failure
- Hypersensitivity to beta-blockers
- Greater than 1st degree heart block
- Sinus bradycardia
- Congestive heart failure (unless secondary to a tachyarrhythmia responsive to beta-blockers)
- Bronchospastic lung disease (e.g., feline asthma)
- Bradyarrhythmias
- Acute or decompensated congestive heart failure
- Concurrent administration with alpha-adrenergic agonists (e.g., adrenaline)
不良反應
- Bradycardia
- Lethargy and depression
- Impaired AV conduction
- Congestive heart failure (CHF) or worsening of heart failure
- Hypotension
- Syncope
- Diarrhea
- Hypoglycemia
- Bronchoconstriction
- AV block
- Myocardial depression
- Heart failure
- Hypoglycaemia
- Bronchospasm
- Diarrhoea
- Peripheral vasoconstriction
- Depression
藥物相互作用
- Antacids · May reduce oral propranolol absorption; separate doses by at least one hour
- Anesthetics, General · Additive myocardial depression may occur
- Anticholinergics · May negate cardiac effects of beta-blockers
- Calcium Channel Blockers · Concurrent use should be done with caution due to additive negative inotropic effects, particularly in patients with cardiomyopathy or CHF
- Cimetidine · May decrease the metabolism of propranolol and increase blood levels · moderate
- Diuretics · May increase risk for hypotension · moderate
- Epinephrine · Unopposed alpha effects of epinephrine may lead to rapid increases in blood pressure and decrease in heart rate
- Fluoxetine · May decrease propranolol metabolism; complete heart block reported in one human
- Insulin and Antidiabetic Drugs · Propranolol may prolong the hypoglycemic effects of insulin therapy
- Lidocaine · Clearance may be impaired by propranolol · major
- Methimazole, Propylthiouracil · Propranolol doses may need to be decreased when initiating therapy
- Phenobarbital · May increase the metabolism of propranolol · moderate
監測
- ECG (Electrocardiogram)
- Signs of toxicity (bradycardia, hypotension, lethargy)
- Blood pressure (especially if administering IV)
- Heart rate and rhythm (ECG)
- Blood pressure
- Signs of congestive heart failure (e.g., respiratory rate/effort)
- Blood glucose (especially in diabetic patients receiving insulin)
過量
**Clinical Signs:** The most predominant expected signs are **hypotension** and **bradycardia**. Other possible effects include CNS depression (ranging from depressed consciousness to seizures), bronchospasm, hypoglycemia, hyperkalemia, respiratory depression, pulmonary edema, AV block, or asystole. **Treatment:** * **Decontamination:** If recent oral ingestion, consider emptying the gut and administering activated charcoal. * **Monitoring:** Monitor ECG, blood glucose, potassium, and blood pressure. * **Cardiovascular Support:** Use IV fluids and pressor agents for hypotension. Treat bradycardia with **atropine**; if atropine fails, cautiously administer **isoproterenol**. A transvenous pacemaker may be necessary. * **Heart Failure:** Treat with digoxin, diuretics, oxygen, and IV aminophylline if necessary. * **Antidotal Therapy:** **Glucagon** (5-10 mg IV; human dose) may increase heart rate and blood pressure, reducing the cardiodepressant effects of propranolol. * **Seizures:** Generally respond to IV diazepam.
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