Procainamide: veterinary dose and monograph

At a glance

Drug class

Cardiovascular

Also known as

Pronestyl, Procainamide HCl

Species with doses

Dogs, Cats and Horses

General dose range

10–25 mg/kg PO q6–8h (PO) / CRI (IV) — check the species tables for the indication

Routes

PO, IV

Last reviewed

1 October 2026

Indications

• Ventricular tachycardia / frequent ventricular premature complexes (IV acute, PO maintenance)
• Ventricular arrhythmias unresponsive to lidocaine
• Recent-onset atrial fibrillation in horses (selected conversion protocols)
• Supraventricular tachyarrhythmias (some)

Procainamide dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Dogs

• Ventricular arrhythmia — maintenance (PO): Papich 5e: 10–30 mg/kg PO q6h, to a maximum of 40 mg/kg. Plumb’s p.1007: 20–30 mg/kg PO q6–8h (older 8–20 mg/kg recommendations are almost certainly too low — Kittleson); sustained-release 20 mg/kg q8h (Hogan). Titrate with ECG/Holter.
• Ventricular arrhythmia — acute (IV): Plumb’s p.1007: 2–4 mg/kg IV over 2 min, repeated to a total of 12–20 mg/kg (Kittleson); 6–8 mg/kg over 3–5 min (Fine; Hogan); 10–15 mg/kg over 1–2 min (Moise). Papich 5e: 8–20 mg/kg IV or IM; CRI loading 10 mg/kg. Monitor ECG and blood pressure; stop at QRS widening or hypotension.
• Ventricular arrhythmia — CRI: Papich 5e: 10 mg/kg IV loading dose then 20 µg/kg/min, increased to 25–50 µg/kg/min for refractory arrhythmias. Plumb’s p.1007: 10–40 µg/kg/min (Kittleson); 25–50 µg/kg/min (Moise); up to 40–100 µg/kg/min after a 6.6–8.8 mg/kg load (Fine).

Cats

• Ventricular tachyarrhythmia: Papich 5e and Plumb’s p.1007 (Ware 2000): 1–2 mg/kg slowly IV, then a CRI of 10–20 µg/kg/min. Monitor ECG and blood pressure.
• Arrhythmia — CRI: Papich 5e and Plumb’s p.1007 (Ware 2000): 10–20 µg/kg/min IV.
• SVT / arrhythmia — maintenance: Papich 5e: 3–8 mg/kg IM or PO q6–8h. Plumb’s p.1007: 3–8 mg/kg PO q6–8h (Wright 2000); Ware 2000 lists 7.5–20 mg/kg PO q6–8h.

Horses

• Ventricular arrhythmia - oral maintenance: Papich 5e and Plumb’s p.1007: 25–35 mg/kg PO q8h.
• Ventricular tachycardia / atrial fibrillation — IV titration: Papich 5e: 1 mg/kg IV in increments, up to a total maximum of 20 mg/kg. Plumb’s p.1007: 1 mg/kg/min IV, not exceeding 20 mg/kg (20 min) in total (Kimberly & McGurrin; Mogg); less effective than quinidine for atrial fibrillation. Monitor ECG and blood pressure continuously; stop at QRS widening or hypotension. ARCI Class 4.

Contraindications

High-grade AV block / severe bradyarrhythmia without pacing. Significant pre-existing QT prolongation. Myasthenia gravis (worsens). Hypotension/cardiogenic shock. Significant renal impairment (NAPA accumulation — reduce dose). Known hypersensitivity. Caution combining antiarrhythmics.

Species-specific warnings

Horses: AF conversion in horses is specialist territory with proarrhythmic risk — ECG monitoring essential; quinidine is the more traditional equine agent.

Adverse effects

• Hypotension (especially rapid IV)
• Proarrhythmia (QT prolongation, torsades), AV block
• GI upset (oral)
• Negative inotropy; weakness

Drug interactions

• Other QT-prolonging/antiarrhythmic drugs: additive proarrhythmia
• Other negative inotropes/chronotropes: additive cardiac depression
• Anticholinergics: additive (procainamide has vagolytic effects)
• Cimetidine: raises procainamide/NAPA levels (reduced clearance)
• Neuromuscular blockers: potentiated

Pregnancy and lactation

Limited data; use only if the maternal arrhythmia risk outweighs potential fetal risk.

Monitoring

• ECG/Holter — efficacy AND QT/QRS (proarrhythmia)
• Blood pressure (especially during IV use)
• Renal function (NAPA accumulation — dose adjustment)
• Signs of CHF; electrolytes (K/Mg)

Toxicity and overdose

Overdose: hypotension, widened QRS/QT, AV block, proarrhythmia (torsades), and myocardial depression. NAPA accumulates in renal impairment, prolonging effect/toxicity. Rapid IV causes hypotension. (Chronic human use causes a lupus-like syndrome; less defined in animals.)

Management: No specific antidote. Stop the drug; IV fluids/vasopressors for hypotension, IV sodium bicarbonate for severe QRS widening (sodium-channel-blocker toxicity), IV magnesium for torsades, and supportive cardiac care; continuous ECG. Reduce dose/avoid in renal impairment.

Clinical pearls

• A class IA option for ventricular arrhythmias when lidocaine fails — IV (bolus + CRI) acutely, oral for maintenance
• Watch the QT/QRS: it (and its metabolite NAPA) can be proarrhythmic — give IV slowly and reduce the dose in renal impairment
• In horses it features in some atrial-fibrillation conversion protocols (quinidine is the traditional equine choice)
• Sodium bicarbonate is the key intervention for severe QRS-widening (Na-channel-blocker) toxicity

Mechanism of action

A class IA antiarrhythmic that blocks fast sodium channels (slowing conduction and phase-0 depolarisation) and also blocks potassium channels (prolonging the action potential and refractory period). This suppresses re-entrant and automatic ventricular arrhythmias. The potassium-channel effect (and that of its active metabolite N-acetylprocainamide, NAPA) prolongs the QT — the basis of its proarrhythmic (torsades) risk.

Formulations and products

• Injection 100 mg/mL
• 250 / 500 mg tablet/capsule
• Pronestyl / Procainamide — 100 mg/mL injection; 250 / 500 mg tablet, Injection / tablet (human-label)

Storage

Tablets/injection: 15–30 °C, protect from light; do not use discoloured injection.

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

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• Pimobendan
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• Quinidine
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• Sildenafil

Frequently asked questions