アテノロール
アテノロールは、主に小動物の全身性高血圧および頻脈性不整脈の管理に使用される心臓選択性β遮断薬です。肺水腫を伴わない肥大型心筋症（HCM）の猫において、動的流出路閉塞を軽減し、拡張期の心室充満を改善するためによく使用されます。 **主な特徴:** * **心臓選択性:** 通常の用量ではβ2受容体への作用が最小限であるため、プロプラノロールのような非選択性β遮断薬と比較して、喘息や気管支痙攣のある患者に対して比較的安全に使用できます。 * **陰性変力作用:** うっ血性心不全（CHF）、腎不全、または洞不全症候群の患者には極めて慎重に使用する必要があります。 * **代謝への影響:** 高用量では甲状腺機能亢進症や低血糖の臨床症状を隠蔽する可能性があります。また、高血糖または低血糖を引き起こす可能性があるため、不安定な糖尿病患者には注意が必要です。 **臨床のポイント:** プロプラノロールとは異なり、アテノロールは非常に水溶性が高い薬剤です。脂溶性が低いため、血液脳関門をほとんど通過せず、結果として中枢神経系（CNS）の副作用（嗜眠やうつ状態など）が著しく少なくなります。主に未変化体のまま腎臓から排泄されるため、重度の腎機能障害がある患者では用量調整が必要になる場合があります。
作用機序: 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.
動物種別の用量
- 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
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
- Overt heart failure
- Hypersensitivity to beta-blockers
- Greater than first-degree heart block
- Sinus bradycardia
- Cats with hypertrophic cardiomyopathy with accompanying pulmonary edema
有害事象
- Lethargy
- Hypotension
- Diarrhea
- Bradycardia
- Inappetence
- Depression
- Impaired AV conduction
- Worsening of heart failure
- Hypoglycemia
- Syncope
- Bronchoconstriction (rare at normal doses)
薬物相互作用
- 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.
モニタリング
- Cardiac function
- Pulse rate
- ECG (if necessary)
- Blood pressure (if indicated)
- Signs of toxicity (lethargy, hypotension, bradycardia)
過量投与
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.
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。