Digoxin-quinidine interaction in the dog

Area of Science:

• Veterinary Pharmacology
• Clinical Toxicology

Background:

• Digoxin is a cardiac glycoside used to treat heart failure and arrhythmias.
• Quinidine is an antiarrhythmic drug that can interact with other medications.
• Understanding drug interactions is crucial for safe and effective veterinary treatment.

Purpose of the Study:

• To investigate the pharmacokinetic and clinical effects of co-administering quinidine with digoxin in healthy dogs.
• To evaluate the potential for quinidine to alter digoxin plasma concentrations and induce toxicity.

Main Methods:

• Seven healthy dogs received oral digoxin, followed by the addition of oral quinidine.
• Plasma concentrations of digoxin and quinidine were monitored.
• Electrocardiograms (ECGs) and physical signs of toxicity were assessed in a subset of dogs.

Main Results:

• Co-administration of quinidine significantly increased mean steady-state plasma digoxin concentrations (1.4 to 2.3 ng/ml).
• Dogs exhibited vomiting and anorexia when quinidine was added to digoxin treatment.
• While digoxin alone increased the PQ-interval, quinidine did not cause further ECG changes.

Conclusions:

• Quinidine significantly elevates plasma digoxin levels in dogs, increasing the risk of digitalis toxicity.
• Clinicians should exercise caution when prescribing quinidine concurrently with digoxin in canine patients.
• Monitoring for signs of toxicity and adjusting dosages may be necessary when these drugs are used together.