디고신

강심배당체

디고신은 주로 양성 변력 작용(심근 수축력 증가) 및 음성 변시 작용(심박수 감소)을 위해 사용되는 강심배당체입니다. 수의학에서는 울혈성 심부전(CHF) 및 심방세동이나 조동과 같은 상심실성 빈맥 치료에 사용됩니다. **임상 요점:** * **좁은 치료 지수:** 치료 용량과 독성 용량 사이의 차이가 매우 작습니다. 신중한 용량 설정과 치료 약물 농도 모니터링(TDM)이 필수적입니다. * **치료 패러다임의 변화:** 역사적으로 CHF 관리의 핵심이었으나, 피모벤단과 같이 더 안전하고 효과적인 약물의 등장으로 더 이상 개와 고양이의 심부전 1차 치료제로 간주되지 않습니다. 현재는 주로 심방세동의 심박수 조절을 위해 딜티아젬과 함께 보조적으로 사용됩니다. * **용량 기준:** 디고신은 지방이나 복수로 잘 분포되지 않으므로 반드시 **제지방 체중(Lean body weight)**을 기준으로 용량을 설정해야 합니다. * **종 특이적 민감도:** 고양이는 개에 비해 디고신 독성에 매우 민감합니다.

작용 기전: Digoxin exerts its effects through the reversible inhibition of the **Na⁺/K⁺-ATPase** pump in the myocardial cell membrane. * **Positive Inotropy (Contractility):** Inhibition of **Na⁺/K⁺-ATPase** → Increased intracellular Na⁺ → Decreased driving force for the **Na⁺/Ca²⁺ exchanger (NCX)** → Decreased Ca²⁺ extrusion → Increased intracellular Ca²⁺ → Increased Ca²⁺ uptake into the sarcoplasmic reticulum. Upon the next action potential, more Ca²⁺ is released, leading to increased myocardial contractility. * **Negative Chronotropy/Dromotropy (Heart Rate/Conduction):** Digoxin increases vagal (parasympathetic) tone → Decreased conduction velocity through the **AV node** and prolonged effective refractory period (ERP) → Slowed ventricular response rate in supraventricular arrhythmias. * **Neurohormonal Effects:** At low doses, digoxin restores baroreceptor sensitivity, which decreases sympathetic outflow and reduces the neurohormonal activation seen in heart failure.

동물 종별 용량

Cats

Dilated cardiomyopathy or advanced atrioventricular valve insufficiency · 0.007 mg/kg PO every other day · PO · q48h · Use lean body weight. Measure serum level 10+ days later, 8-10 hours after dosing. Therapeutic level: 1-2 ng/mL.
Starting dose for normal cats weighing less than 3 kg · 1/4th of a 0.125 mg tablet administered every other day · PO · q48h · Tablets are better tolerated than the alcohol-based elixir.
Starting dose for normal cats weighing 3 to 6 kg · 1/4th of a tablet every day · PO · q24h · Using 0.125 mg tablet.
Starting dose for normal cats weighing more than 6 kg · 1/4th of a tablet every day to q12h · PO · q12h-q24h · Using 0.125 mg tablet.
Management of supraventricular tachyarrhythmias · 10 μg/kg (equating to 1/4 of a 125 μg tablet). Start at lower dose range and titrate up. · PO · q24-48h · Long-term · Cats are highly sensitive to toxicity.
Management of supraventricular tachyarrhythmias (Emergency/Rare) · 1-1.6 μg/kg · IV · q12h · As needed · Only use IV if essentially indicated. Administer very slowly.

Ferrets

Dilated cardiomyopathy · 0.01 mg/kg PO once daily initially · PO · q24h · Use oral liquid. May increase to twice daily if necessary.
Maintenance · 0.005-0.01 mg/kg PO once to twice daily · PO · q12h-q24h · Using the elixir; monitor blood levels if possible.
Dilated cardiomyopathy long-term maintenance · 0.01 mg/kg q24h · PO · q24h · Long-term · Used with furosemide (2 mg/kg q12h) and enalapril (0.5 mg/kg q48h).

투여 경로

POIV

금기

Ventricular fibrillation
Digitalis intoxication
Hypertrophic cardiomyopathy in cats (relative contraindication, may increase myocardial oxygen demand and dynamic outflow obstruction)
Frequent ventricular arrhythmias
Atrioventricular (AV) block
Feline hypertrophic cardiomyopathy
Hypokalaemia

이상반응

Cardiac arrhythmias (complete or incomplete heart block, bigeminy, ST segment changes, paroxysmal ventricular or atrial tachycardias, multifocal VPCs)
Mild GI upset
Anorexia
Weight loss
Diarrhea
Vomiting (especially associated with IV injections)
Vomiting
Diarrhoea
Depression
Arrhythmias (AV block, bigeminy, paroxysmal ventricular or atrial tachycardias with block, multiform VPCs)
Vasoconstriction (with IV administration)

약물 상호작용

Aminosalicylic Acid · May reduce digoxin serum levels
Antacids · May reduce digoxin serum levels · moderate
Chloramphenicol · May reduce digoxin serum levels in dogs
Cholestyramine · May reduce digoxin serum levels
Cimetidine · May reduce digoxin serum levels · moderate
Metoclopramide · May reduce digoxin serum levels · moderate
Neomycin (Oral) · May reduce digoxin serum levels
Phenobarbital · May reduce digoxin serum levels
St John's Wort · May reduce digoxin serum levels
Sucralfate · May reduce digoxin serum levels
Sulfasalazine · May reduce digoxin serum levels
Amiodarone · May increase serum levels, decrease elimination rate, or enhance toxic effects · major
Anticholinergics · May increase serum levels, decrease elimination rate, or enhance toxic effects
Captopril (or other ACEIs) · May increase serum levels, decrease elimination rate, or enhance toxic effects

모니터링

Serum digoxin levels (Trough levels recommended: Dogs 0.8-1.2 ng/mL; Cats 0.9-2 ng/mL; Other species 0.5-2 ng/mL. Wait at least 6 days after starting therapy to reach steady-state)
Appetite and body weight
Cardiac rate and ECG changes
Serum electrolytes (especially potassium)
Renal function tests
Clinical efficacy for CHF (improved perfusion, decreased edema)
Serum digoxin levels (check after 7-10 days, sample taken 6-8 hours post-pill. Ideal trough therapeutic level: 0.6-1.2 ng/ml)
ECG (monitor for AV block and ventricular arrhythmias)
Serum potassium levels (hypokalaemia increases toxicity risk)
Renal function (BUN, Creatinine)

과용량

**Acute Toxicity:** In dogs, the acute toxic dose after IV administration is reported to be 0.177 mg/kg. **Treatment of Toxicity:** * **Chronic Toxicity:** Often resolves by temporarily stopping the drug and reevaluating the dosage regimen. * **Acute Ingestion:** If recent and no cardiotoxic/neurologic signs are present, empty the stomach followed by activated charcoal. Repeated charcoal administration may be beneficial due to enterohepatic recirculation. Anion-exchange resins (colestipol, cholestyramine) can reduce absorption but are rarely available. * **Supportive Care:** Continuous ECG monitoring, correct acid-base/hypoxia/fluid/electrolyte imbalances. *Note: Potassium use in normokalemic patients is controversial and requires expertise.* * **Antiarrhythmics:** Lidocaine and phenytoin are commonly used for life-threatening digitalis-induced arrhythmias. Atropine may treat sinus bradycardia, SA arrest, or AV block. * **Antidote:** **Digoxin immune Fab** (ovine antibodies) binds directly to the drug, inactivating it. It is highly effective but very expensive, and veterinary experience is limited.

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