阿替洛爾
阿替洛爾（Atenolol）是一種心臟選擇性β-受體阻斷劑，主要用於控制小動物的全身性高血壓和心搏過速性心律不整。它常被用於患有肥厚性心肌病（HCM）且無併發肺水腫的貓咪，以減少動態性流出通道阻塞並改善舒張期充盈。 **主要特點：** * **心臟選擇性：** 在常規劑量下對β2受體的作用極小，因此對於患有氣喘或支氣管痙攣的病患，比非選擇性β-受體阻斷劑（如普萘洛爾）相對安全。 * **負性肌力作用：** 對於鬱血性心衰竭（CHF）、腎衰竭或竇房結功能障礙的病患，必須極度謹慎使用。 * **代謝影響：** 較高劑量可能會掩蓋甲狀腺功能亢進或低血糖的臨床症狀。它也可能引起高血糖或低血糖，因此在血糖不穩定的糖尿病患中需謹慎使用。 **臨床要點：** 與普萘洛爾不同，阿替洛爾具有高度水溶性。它的脂溶性低，這意味著它極少穿透血腦屏障，因此中樞神經系統（CNS）副作用（如嗜睡或抑鬱）顯著較少。由於它主要以原形經腎臟排泄，對於有顯著腎功能損害的病患可能需要調整劑量。
作用機制: Atenolol acts as a competitive, relatively specific antagonist at **β1-adrenergic receptors** located primarily in the myocardium. * **Pathway:** Blockade of β1-receptors → decreased intracellular cAMP → reduced intracellular calcium influx. * **Cardiovascular Effects:** This leads to negative chronotropic (decreased sinus heart rate) and negative inotropic (decreased contractility) effects. It slows AV conduction, diminishes cardiac output at rest and during exercise, and significantly decreases myocardial oxygen demand. * **Blood Pressure:** Reduces systemic blood pressure through decreased cardiac output and potentially decreased renin release from the kidneys. * **Selectivity Loss:** At higher dosages, β1 specificity may be lost, leading to **β2-receptor** blockade (which can cause bronchoconstriction and peripheral vasoconstriction). * Atenolol lacks intrinsic sympathomimetic activity (ISA) and membrane-stabilizing activity.
各物種劑量
- Treatment of hypertension or cardiac conditions (e.g., hypertrophic cardiomyopathy) · 3 mg/kg PO q12h (or 6.25 -12.5 mg total dose) PO q12h · PO · q12h
- Treatment of hypertension or cardiac conditions · 6.25-12.5 mg (total dose per cat) q12h · PO · q12h
- Treatment of choice for hyperthyroid, hypertensive cats · 6.25-12.5 mg (total dose) PO q12-24h · PO · q12-24h · Beta-blockers are rarely sufficient alone to treat hypertension due to other causes.
- Hypertrophic cardiomyopathy · 6.25 mg (total dose) PO once daily · PO · q24h
- Hypertrophic cardiomyopathy · 3.13-6.25 mg (total dose) PO once daily · PO · q24h
- Cardiac arrhythmias, obstructive heart disease, hypertension, myocardial infarction, etc. · 0.3-0.6 mg/kg PO q12h · PO · q12h · For refractory VTach combine with mexiletine (5-8 mg/kg PO q8h)
- Moderate to severe sub-valvular aortic stenosis (SAS) · 0.5-1 mg/kg PO twice a day · PO · q12h
- To attempt to decrease syncopal episodes associated with pulmonic stenosis · 0.25-1 mg/kg PO twice a day · PO · q12h
- Hypertension · 0.25-1 mg/kg PO q12h · PO · q12h
劑量為合格獸醫專業人員的臨床參考。請務必對照最新藥品仿單及個別病患確認。
給藥途徑
禁忌症
- Overt heart failure
- Hypersensitivity to beta-blockers
- Greater than first-degree heart block
- Sinus bradycardia
- Cats with hypertrophic cardiomyopathy with accompanying pulmonary edema
不良反應
- Lethargy
- Hypotension
- Diarrhea
- Bradycardia
- Inappetence
- Depression
- Impaired AV conduction
- Worsening of heart failure
- Hypoglycemia
- Syncope
- Bronchoconstriction (rare at normal doses)
藥物相互作用
- Anesthetics (myocardial depressants) · Additive myocardial depression may occur with concurrent use.
- Calcium-Channel Blockers (e.g., diltiazem, verapamil, amlodipine) · Concurrent use should be done with caution due to additive negative inotropic effects, particularly in patients with preexisting cardiomyopathy or CHF.
- Clonidine · Atenolol may exacerbate rebound hypertension after stopping clonidine therapy.
- Furosemide, Hydralazine, or other hypotensive drugs · May increase the hypotensive effects of atenolol.
- Phenothiazines · Concurrent use may exhibit enhanced hypotensive effects.
- Reserpine · Potential for additive effects including hypotension and bradycardia.
- Sympathomimetics (e.g., metaproterenol, terbutaline, epinephrine, phenylpropanolamine) · May have their actions blocked by atenolol, and they may in turn reduce the efficacy of atenolol.
監測
- Cardiac function
- Pulse rate
- ECG (if necessary)
- Blood pressure (if indicated)
- Signs of toxicity (lethargy, hypotension, bradycardia)
過量
Common clinical signs of overdose include lethargy and vomiting. Severe overdose represents extensions of the drug's pharmacologic effects: **hypotension, bradycardia, bronchospasm, cardiac failure, hypoglycemia, and hyperkalemia**. **Treatment:** * If recent oral ingestion: consider emptying the gut and administering activated charcoal. * **Monitor:** ECG, blood glucose, potassium, and blood pressure. * **Cardiovascular support:** Symptomatic treatment. Use fluids and pressor agents (dopamine or norepinephrine) for hypotension. * **Bradycardia:** Treat with atropine. If atropine fails, isoproterenol given cautiously is recommended. * **Metabolic:** Insulin and dextrose may be needed for hyperkalemia and hypoglycemia. * **Advanced support:** A transvenous pacemaker may be necessary. Cardiac failure can be treated with a digitalis glycoside, diuretics, and oxygen. * **Antidote:** Glucagon (5-10 mg IV; human dose) may increase heart rate and blood pressure and reduce the cardiodepressant effects of atenolol.
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