Quinidine Sulfate Powder Packet

Class IA antiarrhythmic for atrial fibrillation in horses; pharmacological cardioversion. Class IA antiarrhythmic sodium channel blocker. Mechanism: frequency-dependent blockade of voltage-gated sodium channels → slows phase 0 depolarization and conduction velocity; also blocks potassium channels (IKr) → prolongs QT interval and refractoriness. Also anti-vagal (atropine-like) effects in atria. Oral quinidine sulfate used for equine atrial fibrillation pharmacocardioversion. Key information Antiarrhythmic for atrial fibrillation in horses. NARROW THERAPEUTIC INDEX. IV bolus risk of fatal arrhythmias — use only with cardiac monitoring. Oral: administer via nasogastric tube in horses. Drug interactions: increases digoxin levels.

Oral (horses — pharmacocardioversion): administer via nasogastric tube as quinidine sulfate solution q2h with ECG monitoring. IV (horses — quinidine gluconate): dilute in 0.9% NaCl; infuse over 15–20 min with continuous ECG monitoring. Pre-treat with digoxin before quinidine. Discontinue if QRS widens >25% or arrhythmias develop. Store at room temperature; protect from light. If a dose is missed This medication is administered by a veterinarian or veterinary staff in a clinical setting. Missed doses are managed by your veterinary team — contact your veterinarian to reschedule.

Cardiovascular: QT prolongation, AV block, polymorphic VT (torsade de pointes), hypotension, proarrhythmia (dose-dependent). GI: colic, diarrhea, anorexia, mucosal irritation (horses — very common; limit by IV or NG administration). CNS: ataxia, muscle tremors, depression, facial edema, urticaria. Horses: risk of sudden death with rapid IV administration. Narrow therapeutic index — monitor ECG continuously.

For animals Horses: continuous ECG monitoring required during IV administration — stop if QRS widens >25% or if ventricular arrhythmias develop. Pre-treat with digoxin in horses to prevent paradoxical ventricular rate acceleration (atrial fibrillation → rapid ventricular response via vagolytic effect). Drug interaction: digoxin levels increase with concurrent quinidine — reduce digoxin dose by 50%. Narrow therapeutic window — monitor ECG and plasma levels. For people handling this medication Wash hands thoroughly with soap and water after handling. Avoid contact with eyes; if contact occurs, flush with water for 15 minutes and seek medical attention. Keep out of reach of children. If accidental ingestion occurs, contact Poison Control (1-800-222-1222). Class I antiarrhythmic — keep away from children (life-threatening cardiac effects if ingested). Store securely. Keep out of reach of children. Pregnant women and women of childbearing age should avoid contact. Contact Poison Control if ingested.

This is a veterinary emergency. Quinidine overdose causes life-threatening ventricular arrhythmias. Cardiac monitoring and emergency treatment required.