地爾硫卓
地爾硫卓是一種**非二氫吡啶類鈣離子通道阻斷劑**和**第四類抗心律不整藥物**，在獸醫學中主要用於控制貓的上心室性心搏過速 (SVTs)、全身性高血壓、肺動脈高壓以及肥厚性心肌病 (HCM)。 * **心血管作用：** 主要透過減緩房室結 (AV node) 傳導並促進血管擴張發揮作用，對於心房顫動的速率控制非常有效。 * **臨床應用：** 雖然過去是治療貓 HCM 的基石，但近年來針對此適應症的使用已減少，轉而使用其他療法，不過它仍是治療心搏過速的重要藥物。 * **臨床要點：** 與二氫吡啶類（如氨氯地平，為強效周邊血管擴張劑）不同，地爾硫卓對心臟傳導的影響更顯著，因此在節律控制方面較優，但對於嚴重全身性高血壓的降壓效果較弱。
作用機制: Diltiazem exerts its effects by binding to the alpha-1 subunit of **L-type voltage-gated calcium channels**. * **Mechanism:** Inhibits transmembrane influx of extracellular calcium ions → decreases intracellular calcium in myocardial cells and vascular smooth muscle. * **Cardiac Conduction:** Slows **AV node conduction** and prolongs refractory times (negative dromotropic effect). It rarely affects SA node conduction except in sick sinus syndrome. * **Vasodilation:** Relaxes vascular smooth muscle → dilates main systemic and coronary arteries → reduces total peripheral resistance, blood pressure, and cardiac afterload. * **Inotropy:** Can cause mild negative inotropic effects, though rarely of clinical significance compared to verapamil.
各物種劑量
- Treatment of hypertrophic cardiomyopathy (Option A) · 7.5 mg (total dose) PO q8-12h; Long-acting forms: Cardizem CD Capsules: 10 mg/kg once daily. Dilacor XR Capsules: 15-30 mg total dose q12-24h. · PO · q8-24h · Some cats tolerate 60 mg daily, but vomiting may be a problem.
- Treatment of hypertrophic cardiomyopathy (Option B) · 1.75-2.5 mg/kg PO q8h or sustained release (Dilacor) dosed at 30 mg (total dose) PO q12h · PO · q8-12h
- Treatment of hypertrophic cardiomyopathy (Option C) · 7.5-15 mg (total dose) per cat PO q8h. Alternatively, the sustainedrelease products Cardizem CD at 45 mg (total dose) PO q24h or Dilacor XR at 30 mg (total dose; 1/2 of one of the 60 mg tablets found within the capsule) PO q12h can be used. · PO · q8-24h
- Treatment of hypertrophic cardiomyopathy (Option D) · If using standard release formulations: 1-2.5 mg/kg PO q8h; if using sustained release formations: 30-60 mg (total dose per cat) q24h. · PO · q8-24h · Also indicated for supraventricular arrhythmias.
- Treatment of hypertrophic cardiomyopathy (Option E) · Dilacor XR 30 mg/cat PO q24h. · PO · q24h · If cat has minimal tachycardia and a loud S4 gallop, many prefer using diltiazem (over a beta blocker).
- Emergency treatment of supraventricular tachyarrhythmias · Initially, 0.25 mg/kg IV bolus given over 2 minutes; subsequent 0.25 mg/kg boluses may be repeated at 15 minute intervals until conversion occurs or to a maximum (total) dose of 0.75 mg/kg. · IV · q15min
- Acute management of supraventricular tachyarrhythmias · 0.125-0.35 mg/kg IV · IV · As directed
- Chronic management of supraventricular tachyarrhythmias · 7.5 mg (per cat) PO q8h · PO · q8h · Used in combination with digoxin for patients with CHF unless cat has hypertrophic cardiomyopathy and atrial fib, then digoxin not used.
給藥途徑
禁忌症
- Severe hypotension (<90 mm Hg systolic)
- Sick sinus syndrome (unless functioning pacemaker is in place)
- 2nd or 3rd degree AV block (unless functioning pacemaker is in place)
- Acute myocardial infarction
- Radiographically documented pulmonary congestion
- Hypersensitivity to diltiazem
- Second or third degree AV block
- Marked hypotension
- Sick sinus syndrome
- Acute or decompensated congestive heart failure (relative contraindication)
不良反應
- Dogs: Bradycardia (most prominent)
- Cats: Vomiting (especially with 60 mg sustained-release pellets)
- Lethargy
- Anorexia / GI distress
- Hypotension
- Heart block or rhythm disturbances
- CNS effects
- Skin rashes
- Elevations in liver enzymes
- Bradycardia (most common in dogs)
- Vomiting (most common in cats)
- AV block
藥物相互作用
- Anesthetics, General · May increase cardiac depressant effects of diltiazem.
- Benzodiazepines · Diltiazem may increase benzodiazepine levels.
- Beta-Blockers · May increase the likelihood of bradycardia, AV block, or CHF. Diltiazem may substantially increase the bioavailability of propranolol.
- Buspirone · Diltiazem may increase buspirone levels.
- Cisapride · Could potentially increase risk for increased QT intervals.
- Digoxin · Data conflicts regarding pharmacokinetic effects; diligent monitoring of digoxin serum concentrations is required. · moderate
- Cimetidine · May increase plasma diltiazem concentrations; increased monitoring warranted. · moderate
- Ranitidine · May affect diltiazem concentrations, but to a lesser extent than cimetidine.
- Cyclosporine · Diltiazem may increase cyclosporine serum concentrations; monitoring and dosage adjustments may be required.
- Rifampin · May decrease diltiazem levels.
- Quinidine · Diltiazem may increase quinidine serum concentrations; monitoring and dosage adjustments may be required.
- Beta-adrenergic blockers (e.g., propranolol) · Additive negative inotropic and chronotropic effects. Co-administration is not recommended. · major
監測
- ECG / Heart rate
- Blood pressure
- Adverse effects (vomiting, lethargy)
- Heart rate and rhythm (ECG)
- Renal and hepatic function (periodically)
- Serum digoxin levels (if used concurrently)
過量
The oral LD50 in dogs is >50 mg/kg. * **Clinical Signs:** GI signs, heart block, severe bradycardia, hypotension, CNS depression, and heart failure. * **Treatment:** * Gut emptying protocols if recent ingestion. * **Bradycardia/AV Block:** Atropine. If unresponsive to vagal blockade, cautious use of isoproterenol. Fixed block may require temporary transvenous cardiac pacing. * **Hypotension/Heart Failure:** Inotropics (dobutamine, dopamine, isoproterenol) and pressors (norepinephrine). * **Antidote:** A slow intravenous calcium infusion (1 mL/10 kg body weight of 10% calcium gluconate) may be useful for severe acute toxicity.
VetSheet 藥物參考供持牌獸醫專業人員作臨床決策輔助之用,不能取代專業判斷或廠方最新藥品說明書。