딜티아젬

칼슘 채널 차단제 / 제4군 항부정맥제

딜티아젬은 **비디히드로피리딘계 칼슘 채널 차단제**이자 **제4군 항부정맥제**로, 수의학에서는 주로 고양이의 상심실성 빈맥(SVT), 전신 고혈압, 폐동맥 고혈압 및 비대성 심근병증(HCM) 관리에 사용됩니다. * **심혈관계 효과:** 주로 방실결절(AV node) 전도를 늦추고 혈관 확장을 촉진하여 심방세동의 심박수 조절에 매우 효과적입니다. * **임상적 유용성:** 과거에는 고양이 HCM 치료의 핵심이었으나, 최근에는 다른 치료법이 선호되면서 이 적응증에 대한 사용이 감소했습니다. 하지만 빈맥성 부정맥 치료에는 여전히 중요한 약물입니다. * **임상 요점:** 강력한 말초 혈관 확장제인 디히드로피리딘계(예: 암로디핀)와 달리, 딜티아젬은 심장 전도에 미치는 영향이 더 커서 리듬 조절에는 우수하지만 중증 전신 고혈압에 대한 강압 효과는 상대적으로 약합니다.

작용 기전: 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.

동물 종별 용량

Cats

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.

투여 경로

POIV

금기

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)

이상반응

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

약물 상호작용

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

모니터링

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)

과용량

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.

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