Pimobendan, spironolactone, digoxin, sotalol tell me about their usage and their dose rate in dog and cat according to plums and others books
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The library results are from human medicine textbooks. I need to search specifically for veterinary sources — Plumb's Veterinary Drug Handbook is the key reference. Let me search for veterinary-specific content.
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The library does not contain veterinary textbooks (Plumb's or similar). The collection is entirely human medicine references. I'll now use my comprehensive veterinary pharmacology knowledge — which includes Plumb's Veterinary Drug Handbook, the gold standard reference — plus a web search for the most current dosing data.
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Plumb's veterinary drug handbook pimobendan spironolactone digoxin sotalol dog cat dose
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pimobendan dog cat cardiac dose
Note: The medical textbook library does not contain veterinary references (no Plumb's, Ettinger, or other veterinary pharmacology titles). The information below is drawn from Plumb's Veterinary Drug Handbook (9th ed.), Ettinger & Feldman's Textbook of Veterinary Internal Medicine (8th ed.), Tilley's 5-Minute Veterinary Consult, and Small Animal Internal Medicine (Nelson & Couto), which are the standard references cited in veterinary clinical cardiology.
Cardiovascular Drug Reference: Dogs & Cats
1. Pimobendan
Mechanism of Action
Pimobendan is a benzimidazole-pyridazinone derivative with two complementary mechanisms:
- Calcium sensitizer: Increases myofilament sensitivity to calcium → positive inotropy without increasing intracellular Ca²⁺ (and thus without increasing myocardial oxygen demand)
- Phosphodiesterase III inhibitor (PDE-3): Inhibits breakdown of cAMP → vasodilation (both arterial and venous) → reduces preload and afterload
The net effect is a "luso-inotrope": improves contractility AND promotes relaxation, making it ideal for dilated cardiomyopathy (DCM) and advanced mitral valve disease (MVD).
Indications
| Species | Indication |
|---|---|
| Dog | DCM with systolic dysfunction; MVD stage B2 (preclinical, per ACVIM 2019 consensus) and stages C/D; congestive heart failure (CHF) |
| Cat | Hypertrophic cardiomyopathy (HCM) with systolic dysfunction or end-stage (controversial); restrictive/unclassified CM; off-label |
Key landmark study (EPIC trial, 2016): Pimobendan given in preclinical MVD dogs (stage B2 with cardiomegaly) delayed onset of CHF by a median of 15 months compared to placebo — establishing the ACVIM 2019 recommendation to initiate treatment in B2 dogs.
Dose Rates
Dog:
| Indication | Dose | Frequency | Route |
|---|---|---|---|
| CHF / DCM / MVD (stages C–D) | 0.25–0.3 mg/kg | BID (every 12 h) | PO |
| ACVIM B2 (preclinical MVD) | 0.25 mg/kg (rounded to nearest 1.25 mg tablet) rounded to 0.2–0.3 mg/kg | BID | PO |
| Acute decompensated CHF (if oral acceptable) | 0.3 mg/kg | q8h initially, then BID | PO |
- Total daily dose: 0.5–0.6 mg/kg/day divided BID
- Give on an empty stomach (1 hour before or 2 hours after feeding) — food reduces bioavailability by ~30%
- Available as: 1.25 mg, 2.5 mg, 5 mg, 10 mg chewable tablets (Vetmedin®)
Cat:
| Indication | Dose | Frequency | Route |
|---|---|---|---|
| Systolic dysfunction / DCM / end-stage HCM | 1.25 mg/cat (flat dose) | BID | PO |
| Alternative dosing | 0.625–1.25 mg/cat | SID–BID | PO |
- Use is off-label in cats; evidence is extrapolated from canine studies and case series
- Avoid in cats with significant LVOTO (left ventricular outflow tract obstruction) — worsens obstruction
Adverse Effects
- Generally well tolerated
- Possible: tachycardia, hypotension (usually mild)
- Contraindicated in hypertrophic obstructive cardiomyopathy (HOCM)
- Do NOT use in aortic/pulmonic stenosis with systolic function preserved
2. Spironolactone
Mechanism of Action
Aldosterone antagonist — competitively blocks mineralocorticoid receptors in the renal collecting duct → inhibits Na⁺/K⁺-ATPase → promotes sodium and water excretion while retaining potassium (potassium-sparing diuretic).
Additional cardiac benefits:
- Anti-fibrotic effects on myocardium (independent of diuresis)
- Reduces ventricular remodeling in CHF
- Attenuates RAAS-mediated aldosterone breakthrough (common with chronic furosemide/ACE inhibitor use — "aldosterone escape")
Indications
| Species | Indication |
|---|---|
| Dog | CHF (MVD, DCM) — adjunct to furosemide + ACEi ± pimobendan; hyperaldosteronism (Conn's syndrome); hepatic ascites; edema refractory to loop diuretics |
| Cat | CHF (adjunct); primary hyperaldosteronism (adrenal tumor — most common use in cats); hypertension secondary to hyperaldosteronism |
The QUEST trial (2007) showed a survival benefit of spironolactone (2 mg/kg/day) added to standard CHF therapy in dogs with MVD, though the study had limitations. It remains part of the standard CHF protocol in dogs.
Dose Rates
Dog:
| Indication | Dose | Frequency | Route |
|---|---|---|---|
| CHF (adjunct) | 2 mg/kg | SID or divided BID | PO |
| Hyperaldosteronism | 1–2 mg/kg | BID | PO |
| Anti-fibrotic / cardioprotection | 2 mg/kg | SID | PO |
Cat:
| Indication | Dose | Frequency | Route |
|---|---|---|---|
| Primary hyperaldosteronism | 2–4 mg/kg | BID | PO |
| CHF (adjunct) | 1–2 mg/kg | SID–BID | PO |
- Available as: 25 mg, 50 mg, 100 mg tablets; compounded liquid (10 mg/mL)
- Tablets can be compounded into palatable liquid for cats
Adverse Effects
- Hyperkalemia — monitor K⁺, especially with ACE inhibitors or ARBs; baseline and recheck at 5–7 days and monthly
- Azotemia — monitor BUN/creatinine
- Facial dermatitis/ulcerative dermatitis in cats — important and unique species-specific adverse effect; cutaneous drug reaction reported in cats on spironolactone — monitor facial skin closely; discontinue if lesions develop
- Gynecomastia (rare in dogs)
- GI signs (nausea, vomiting)
⚠️ Cat warning: Spironolactone has been associated with severe facial ulcerative dermatitis in cats, even at standard doses. Some clinicians avoid it in cats or use it at the lowest effective dose with close monitoring.
3. Digoxin
Mechanism of Action
A cardiac glycoside with two main mechanisms:
- Positive inotropy: Inhibits Na⁺/K⁺-ATPase on myocardial cells → intracellular Na⁺ accumulates → Na⁺/Ca²⁺ exchanger reverses → intracellular Ca²⁺ increases → stronger contraction
- Negative chronotropy / anti-arrhythmic: Increases vagal tone → slows AV nodal conduction → reduces ventricular rate in atrial fibrillation (AF); also has mild direct SA and AV nodal depression
Indications
| Species | Indication |
|---|---|
| Dog | Atrial fibrillation (rate control); supraventricular tachycardia (SVT); CHF with systolic dysfunction (weak inotrope — largely superseded by pimobendan but still used as adjunct for AF) |
| Cat | SVT / atrial fibrillation (rare); very rarely used due to narrow therapeutic index and cats' extreme sensitivity |
In modern canine cardiology, digoxin's role has narrowed to rate control in AF (combined with diltiazem or beta-blockers) and occasionally as a weak positive inotrope in CHF not well controlled on pimobendan. It is rarely a first-line agent.
Dose Rates
Dog:
| Indication | Dose | Frequency | Notes |
|---|---|---|---|
| AF rate control / CHF | 0.005–0.011 mg/kg (5–11 µg/kg) | BID | PO; use lean body weight |
| Elixir (0.05 mg/mL) | same mg/kg | BID | Better absorbed than tablets |
| Maximum dose | 0.375 mg/dog/day (total) | — | Do not exceed regardless of weight |
- Alternatively calculated as: 0.22 mg/m² body surface area, BID
- Dose by lean body weight in obese animals (digoxin does not distribute into fat)
- Large breeds: use lower end of range (0.005 mg/kg BID); giant breeds very sensitive
- Therapeutic serum level: 0.8–2.0 ng/mL (sample 6–8 hours post-dose); check at 7–10 days
- Toxicity range: >2.5 ng/mL
Cat:
| Indication | Dose | Frequency | Notes |
|---|---|---|---|
| SVT / AF | 0.007–0.01 mg/kg | Every 48 hours | PO; cats metabolize very slowly |
| Alternative | 1/4 of a 0.125 mg tablet (≈ 0.031 mg/cat) | q48h | Flat dose for average 4 kg cat |
- Cats are highly sensitive to digoxin toxicity — use the lowest possible dose and monitor closely
- Elixir preferred for accurate dosing in cats
- Therapeutic range in cats: 0.9–2.0 ng/mL (check 8–10 hours post-dose)
- Many cardiologists avoid digoxin in cats entirely due to toxicity risk
Adverse Effects / Toxicity
- Narrow therapeutic index — toxicity is common
- GI signs: anorexia, vomiting, diarrhea (often first sign)
- Cardiac arrhythmias: bradycardia, AV block, ventricular arrhythmias (most dangerous)
- Neurological: lethargy, disorientation (especially cats)
- Predisposing factors: hypokalemia, hypomagnesemia, renal insufficiency, hypothyroidism — all ↑ toxicity risk
- Treatment of toxicity: discontinue, correct electrolytes, anti-arrhythmic therapy, digoxin-specific Fab antibodies (Digibind) in severe cases
Drug Interactions (important)
- Quinidine, verapamil, amiodarone, tetracyclines → increase serum digoxin levels (reduce dose by 50%)
- Kaolin-pectin, antacids → reduce absorption
4. Sotalol
Mechanism of Action
Sotalol is a mixed class II / class III antiarrhythmic:
- Class II: Non-selective beta-adrenergic receptor blocker (L-isomer) → reduces automaticity, slows HR, reduces AV conduction
- Class III: Blocks rapid delayed rectifier K⁺ current (I_Kr) (both D- and L-isomers) → prolongs action potential duration (APD) and refractory period in all cardiac tissue → suppresses ventricular and atrial arrhythmias
The combination makes it effective for both ventricular and supraventricular arrhythmias.
Indications
| Species | Indication |
|---|---|
| Dog | Ventricular tachycardia (VT) — especially Boxer cardiomyopathy (ARVC), German Shepherd VT; atrial fibrillation (rate/rhythm control); SVT; prevention of sudden cardiac death in ARVC |
| Cat | Ventricular arrhythmias; HCM-associated arrhythmias; SVT |
Sotalol is one of the most widely used antiarrhythmics in veterinary cardiology, especially for Boxer ARVC where it has shown efficacy in reducing ventricular ectopy.
Dose Rates
Dog:
| Indication | Dose | Frequency | Route |
|---|---|---|---|
| Ventricular arrhythmias / ARVC | 1–3.5 mg/kg | BID | PO |
| Common starting dose | 1–2 mg/kg | BID | PO |
| SVT / AF rate control | 1–2 mg/kg | BID | PO |
- Start at lower end; titrate up based on response and Holter monitoring
- Available as: 80 mg, 120 mg, 160 mg, 240 mg tablets (human label); compounded suspensions available
Cat:
| Indication | Dose | Frequency | Route |
|---|---|---|---|
| Ventricular / supraventricular arrhythmias | 2 mg/kg | BID | PO |
| Range reported | 1–2 mg/kg | BID | PO |
Adverse Effects
- Proarrhythmia — QT prolongation → torsades de pointes (TdP) — the most serious risk
- Bradycardia, hypotension
- Negative inotropy — contraindicated or use with extreme caution in CHF / systolic dysfunction
- Bronchoconstriction (beta-blockade) — avoid in asthma/bronchospasm
- Fatigue, lethargy
- Baseline ECG and periodic QTc monitoring recommended; if QTc prolongs >25% above baseline, reduce dose or discontinue
- Contraindications: pre-existing AV block, severe bradycardia, hypokalemia/hypomagnesemia (↑ TdP risk), uncompensated heart failure
Summary Comparison Table
| Drug | Class | Primary Use (Dog) | Primary Use (Cat) | Dog Dose | Cat Dose |
|---|---|---|---|---|---|
| Pimobendan | Ca²⁺ sensitizer + PDE-3 inhibitor | MVD, DCM, CHF stages B2–D | Systolic dysfunction (off-label) | 0.25–0.3 mg/kg PO BID | 1.25 mg/cat PO BID |
| Spironolactone | Aldosterone antagonist (K⁺-sparing diuretic) | CHF adjunct, hyperaldosteronism | Primary hyperaldosteronism, CHF adjunct | 2 mg/kg PO SID–BID | 2–4 mg/kg PO BID |
| Digoxin | Cardiac glycoside | AF rate control, weak inotrope | SVT/AF (rarely, with caution) | 0.005–0.011 mg/kg PO BID (max 0.375 mg/day) | 0.007–0.01 mg/kg PO q48h |
| Sotalol | Class II + III antiarrhythmic | VT (ARVC/Boxer), AF, SVT | VT, HCM arrhythmias, SVT | 1–3.5 mg/kg PO BID | 1–2 mg/kg PO BID |
Key References:
- Plumb DC. Plumb's Veterinary Drug Handbook, 9th ed. Wiley-Blackwell, 2018
- Ettinger SJ, Feldman EC, Côté E. Textbook of Veterinary Internal Medicine, 8th ed. Elsevier, 2017
- Boswood A, et al. Effect of pimobendan in dogs with preclinical mitral valve disease. JAVMA 2016 (EPIC Trial)
- Atkins C, et al. ACVIM consensus statement on diagnosis/treatment of myxomatous mitral valve disease in dogs. J Vet Intern Med 2019;33:1127–1140
- Bonagura JD, Twedt DC. Kirk's Current Veterinary Therapy XV. Saunders/Elsevier, 2014> Library note: The medical textbook library available to me contains only human medicine textbooks (no Plumb's, Ettinger, or veterinary titles). The comprehensive answer above is drawn from my training on those veterinary references directly.
Cardiovascular Drug Reference: Dogs & Cats
1. Pimobendan (Vetmedin®)
Mechanism of Action
A benzimidazole-pyridazinone with two synergistic mechanisms:
- Calcium sensitizer — increases myofilament sensitivity to Ca²⁺ → positive inotropy without raising intracellular Ca²⁺ (no increase in myocardial O₂ demand)
- PDE-3 inhibitor — reduces cAMP breakdown → arterial and venous vasodilation (reduces afterload and preload)
Net effect: improves contractility, promotes relaxation, and reduces cardiac workload simultaneously.
Indications
| Species | Indication |
|---|---|
| Dog | MVD stage B2 (preclinical with cardiomegaly, per ACVIM 2019 consensus); MVD/DCM stages C & D (CHF); systolic dysfunction |
| Cat | Systolic dysfunction; end-stage HCM; restrictive/unclassified CM — off-label |
The EPIC Trial (Boswood et al., 2016) established pimobendan in preclinical MVD (B2 dogs), delaying CHF onset by a median of ~15 months vs. placebo.
Dose Rates
Dog:
| Dose | Frequency | Notes |
|---|---|---|
| 0.25–0.3 mg/kg | BID (q12h) | Total daily dose 0.5–0.6 mg/kg |
| 0.3 mg/kg | q8h initially (acute decompensation) | Then step down to BID |
- Give on empty stomach (1 h before or 2 h after food) — food ↓ bioavailability ~30%
- Round dose to nearest tablet size: 1.25 mg / 2.5 mg / 5 mg / 10 mg
Cat:
| Dose | Frequency | Notes |
|---|---|---|
| 1.25 mg/cat (flat dose) | BID | Off-label |
| 0.625–1.25 mg/cat | SID–BID | Lower end for small cats |
- Contraindicated in hypertrophic obstructive cardiomyopathy (HOCM) — worsens LVOTO
- Avoid in aortic or pulmonic stenosis with preserved systolic function
2. Spironolactone (Aldactone®)
Mechanism of Action
Competitive aldosterone antagonist at mineralocorticoid receptors in the renal collecting duct → promotes Na⁺/water excretion while retaining K⁺ (potassium-sparing diuretic).
Additional cardiac benefits beyond diuresis:
- Anti-fibrotic effect on myocardium → reduces ventricular remodeling
- Counteracts aldosterone escape (breakthrough aldosterone secretion that occurs with chronic furosemide + ACEi therapy)
Indications
| Species | Indication |
|---|---|
| Dog | CHF adjunct (MVD, DCM) alongside furosemide + ACEi ± pimobendan; primary hyperaldosteronism; refractory ascites |
| Cat | Primary hyperaldosteronism (adrenal tumor — most common indication in cats); CHF adjunct |
The QUEST trial (2007) suggested a survival benefit with spironolactone (2 mg/kg/day) added to standard CHF therapy in MVD dogs.
Dose Rates
Dog:
| Indication | Dose | Frequency |
|---|---|---|
| CHF / cardioprotection | 2 mg/kg | SID or divided BID |
| Hyperaldosteronism | 1–2 mg/kg | BID |
Cat:
| Indication | Dose | Frequency |
|---|---|---|
| Primary hyperaldosteronism | 2–4 mg/kg | BID |
| CHF adjunct | 1–2 mg/kg | SID–BID |
Key Adverse Effects
- Hyperkalemia — monitor K⁺ at baseline, 5–7 days, then monthly; especially dangerous with ACEi/ARBs
- Azotemia — monitor BUN/Cr
- ⚠️ Cats: ulcerative facial dermatitis — a unique, serious cutaneous drug reaction; inspect facial skin at each recheck; discontinue immediately if lesions appear
- Gynecomastia (rare, dogs)
3. Digoxin (Lanoxin®)
Mechanism of Action
A cardiac glycoside with two mechanisms:
- Positive inotropy — inhibits Na⁺/K⁺-ATPase → intracellular Na⁺ ↑ → Na⁺/Ca²⁺ exchanger reversal → intracellular Ca²⁺ ↑ → stronger contraction
- Negative chronotropy / vagomimetic — increases vagal tone → slows AV nodal conduction → reduces ventricular rate in AF
Indications
| Species | Indication |
|---|---|
| Dog | Atrial fibrillation (rate control); SVT; CHF adjunct (weak inotrope, largely superseded by pimobendan but still used for AF) |
| Cat | SVT, AF — used very rarely due to extreme sensitivity and narrow therapeutic index |
Dose Rates
Dog:
| Dose | Frequency | Notes |
|---|---|---|
| 0.005–0.011 mg/kg (5–11 µg/kg) | BID | Use lean body weight |
| Maximum: 0.375 mg/dog/day total | — | Never exceed regardless of body weight |
| Alternatively: 0.22 mg/m² BSA | BID | Useful for large/giant breeds |
- Large/giant breeds: use lower end (0.005 mg/kg BID)
- Elixir (0.05 mg/mL) preferred — better and more consistent absorption than tablets
- Check serum level 6–8 hours post-dose at day 7–10: therapeutic range 0.8–2.0 ng/mL; toxic >2.5 ng/mL
Cat:
| Dose | Frequency | Notes |
|---|---|---|
| 0.007–0.01 mg/kg | q48h | Cats metabolize digoxin very slowly |
| ≈ 0.031 mg/cat (¼ of 0.125 mg tablet) | q48h | For ~4 kg average cat |
- Use elixir for accurate dosing
- Therapeutic range: 0.9–2.0 ng/mL (sample 8–10 hours post-dose)
- Many veterinary cardiologists avoid digoxin in cats entirely due to toxicity risk
Key Adverse Effects & Toxicity
- Narrow therapeutic index — toxicity common
- GI: anorexia, vomiting, diarrhea (often first signs)
- Cardiac: bradycardia, AV block, ventricular arrhythmias
- Neurological: lethargy, disorientation (especially cats)
- Predisposing factors for toxicity: hypokalemia, hypomagnesemia, renal insufficiency, hypothyroidism
- Treatment: discontinue drug, correct electrolytes; digoxin-specific Fab antibodies (Digibind/DigiFab) for life-threatening toxicity
Critical Drug Interactions:
- Quinidine, verapamil, amiodarone, tetracyclines → ↑ serum digoxin levels (reduce digoxin dose by ~50% if co-administered)
4. Sotalol (Betapace®)
Mechanism of Action
A mixed Class II + Class III antiarrhythmic:
- Class II (beta-blocker) — L-isomer blocks β₁/β₂ adrenergic receptors → ↓ automaticity, ↓ HR, ↓ AV conduction velocity
- Class III (K⁺ channel blocker) — both isomers block the rapid delayed rectifier K⁺ current (I_Kr) → prolongs action potential duration and refractory period → suppresses re-entrant ventricular and supraventricular arrhythmias
Indications
| Species | Indication |
|---|---|
| Dog | Ventricular tachycardia (primary drug for Boxer ARVC, German Shepherd VT); AF; SVT; prevention of sudden cardiac death in arrhythmogenic cardiomyopathy |
| Cat | Ventricular arrhythmias; HCM-associated arrhythmias; SVT |
Sotalol is one of the most commonly used antiarrhythmics in veterinary cardiology, particularly for Boxer ARVC where it effectively reduces ventricular ectopy burden on Holter monitoring.
Dose Rates
Dog:
| Dose | Frequency | Notes |
|---|---|---|
| 1–3.5 mg/kg | BID | Start low, titrate up |
| Common starting dose: 1–2 mg/kg | BID | Guide titration by Holter + clinical response |
Cat:
| Dose | Frequency | Notes |
|---|---|---|
| 1–2 mg/kg | BID | Start at 1 mg/kg |
Key Adverse Effects
- QT prolongation → Torsades de Pointes (TdP) — most serious risk; monitor ECG (QTc) at baseline and after dose increases; if QTc prolongs >25% above baseline, reduce dose
- Bradycardia, hypotension
- Negative inotropy — use with great caution or avoid in CHF/systolic dysfunction
- Bronchoconstriction — avoid in animals with reactive airway disease
- Contraindications: pre-existing AV block, severe bradycardia, uncompensated heart failure, hypokalemia/hypomagnesemia (↑ TdP risk)
Summary Table
| Drug | Class | Primary Use — Dog | Primary Use — Cat | Dog Dose | Cat Dose |
|---|---|---|---|---|---|
| Pimobendan | Ca²⁺ sensitizer + PDE-3i | MVD (B2–D), DCM, CHF | Systolic dysfunction (off-label) | 0.25–0.3 mg/kg PO BID | 1.25 mg/cat PO BID |
| Spironolactone | Aldosterone antagonist | CHF adjunct; hyperaldosteronism | Primary hyperaldosteronism | 2 mg/kg PO SID–BID | 2–4 mg/kg PO BID |
| Digoxin | Cardiac glycoside | AF rate control; SVT | SVT/AF (rarely; avoid if possible) | 0.005–0.011 mg/kg PO BID (max 0.375 mg/day) | 0.007–0.01 mg/kg PO q48h |
| Sotalol | Class II + III antiarrhythmic | VT (Boxer ARVC), AF, SVT | VT, HCM arrhythmias | 1–3.5 mg/kg PO BID | 1–2 mg/kg PO BID |
References:
- Plumb DC. Plumb's Veterinary Drug Handbook, 9th ed. Wiley-Blackwell, 2018
- Ettinger SJ, Feldman EC, Côté E. Textbook of Veterinary Internal Medicine, 8th ed. Elsevier, 2017
- Atkins C et al. ACVIM consensus guidelines on MVD in dogs. J Vet Intern Med 2019;33:1127–1140
- Boswood A et al. Effect of pimobendan in dogs with preclinical MVD (EPIC Trial). J Vet Intern Med 2016;30:1765–1779
- Tilley LP, Smith FWK. The 5-Minute Veterinary Consult: Canine and Feline, 6th ed. Wiley-Blackwell
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