Quinidine - Page 1

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  • Cardiac arrhythmias are common in animals with heart disease. Irregular heart rhythms originating in the ventricles – the lower chambers of the heart – are potentially dangerous. These rhythm disturbances can lead to low blood pressure, fainting or sudden death if particularly severe.
  • Drugs that make the heart less irritable and suppress abnormal electrical activity are classified as antiarrhythmic drugs. Quinidine is a Class IA antiarrhythmic drug, with properties similar to another heart drug called procainamide.
  • Quinidine affects the electrical activity of the heart cell membrane, impairing the entry of sodium ions and making heart cells less likely to be stimulated prematurely.
  • Quinidine is a prescription drug and can only be obtained from a veterinarian or by prescription from a veterinarian.
  • This drug is not approved for use in animals by the Food and Drug Administration but it is prescribed legally by veterinarians as an extra-label drug.

    Brand Names and Other Names

  • This drug is registered for use in humans only.
  • Human formulations: Quinaglute® (Berlex), Cardioquin® (Purdue-Frederick), Quinidex® (Robins) and various generic preparations
  • Veterinary formulations: None

    Uses of Quinidine

  • Quinidine is used in the treatment of premature ventricular complexes (PVCs or VPCs), ventricular tachycardia and some supraventricular tachycardias. These are heart rhythms originating outside of the normal pacemaker sites within the heart.
  • Quinidine can be administered by injection in the hospital and is often done so in the treatment of cardiac arrhythmias associated with metabolic illness, infections and surgery. Oral quinidine – typically a long-acting form – is sometimes used in the treatment of dogs with heart muscle disease (cardiomyopathy); however, there are better alternatives for this (such as sotalol or mexiletine).

    Precautions and Side Effects

  • While generally safe and effective when prescribed by a veterinarian, quinidine can cause side effects in some animals.
  • Quinidine should not be used in animals with known hypersensitivity or allergy to the drug.
  • It should not be given when there is an electrical disturbance called second-degree or third-degree heart block.
  • Do not use quinidine in dogs diagnosed with the neuromuscular disease myasthenia gravis because quinidine can inhibit the anticholinestearease drugs used to treat this disorder.
  • It should be used with caution in animals diagnosed with diseases of the liver.
  • In animals with congestive heart failure the drug can depress further the contraction of the heart muscle. In such cases, quinidine should be used very cautiously, if at all.
  • Quinidine may interact with other medications. Consult with your veterinarian to determine if other drugs your pet is receiving could interact with quinidine. Such drugs include phenobarbital, muscle relaxants, digoxin, cimetidine and some other heart drugs.
  • Among the more common side effects seen are vomiting , diarrhea, anorexia, weakness and low blood pressure (hypotension).
  • Quinidine can worsen some cardiac arrhythmias leading to a life threatening rhythm disturbance called polymorphic ventricular tachycardia.

    How Quinidine Is Supplied

  • Quinidine is available in 200 mg, 275 mg, 300 mg and 324 mg tablets.
  • Quinidine is also available in 80 mg/ml injectable concentration.

    Dosing Information

  • Medication should never be administered without first consulting your veterinarian.
  • The dose of quinidine in dogs is 3 to 10 mg per pound (6 to 20 mg/kg) in the muscle. Orally 4 to 8 mg per pound (8 to 16 mg/kg) every six to eight hours depending on the preparation used.
  • The duration of administration depends on the condition being treated, response to the medication and the development of any adverse effects. Be certain to complete the prescription unless specifically directed by your veterinarian. Even if your pet feels better, the entire treatment plan should be completed to prevent relapse or prevent the development of resistance.

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