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Digitoxin-quinidine interaction: pharmacokinetic evaluation

P E Fenster, J R Powell, P E Graves

Annals of Internal Medicine

|November 1, 1980

Summary

This summary is machine-generated.

Quinidine significantly alters digitoxin pharmacokinetics in healthy adults. This drug interaction prolongs digitoxin

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Area of Science:

Pharmacology
Clinical Pharmacology
Drug Interactions

Background:

Digitoxin is a cardiac glycoside used for heart failure and arrhythmias.
Quinidine is an antiarrhythmic drug with known drug interaction potential.
Understanding quinidine's effect on digitoxin is crucial for patient safety.

Purpose of the Study:

To evaluate the impact of quinidine on the single-dose pharmacokinetics of digitoxin.
To quantify changes in digitoxin's elimination half-life, clearance, and volume of distribution when co-administered with quinidine.

Main Methods:

A pharmacokinetic study in five healthy adult subjects.
Single intravenous digitoxin administration, with and without concurrent oral quinidine treatment.
Serial blood sampling for 3 weeks and urine collection for 4 days post-digitoxin dose.

Main Results:

Quinidine significantly prolonged digitoxin's elimination half-life (174 to 261 hours).
Total body clearance and renal clearance of digitoxin were significantly reduced by quinidine (p < 0.05).
Serum digitoxin levels increased, while volume of distribution and protein binding remained unchanged.

Conclusions:

Quinidine administration alters digitoxin pharmacokinetics, leading to reduced clearance and prolonged half-life.
The observed changes suggest a potential for increased digitoxin toxicity when used with quinidine.
The interaction mechanism may differ partly from that seen with digoxin.