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Quinidine-digoxin interaction: Pharmacokinetics, underlying mechanism and clinical implications
The New England Journal of Medicine
|August 23, 1979
Summary
Concurrent administration of quinidine with digoxin significantly elevates serum digoxin levels and reduces renal clearance. This interaction necessitates a dose reduction of digoxin to prevent potential digitalis intoxication.
Area of Science:
- Pharmacology
- Clinical Medicine
Background:
- Digoxin is a cardiac glycoside used to treat heart failure and arrhythmias.
- Quinidine is an antiarrhythmic drug.
- Interactions between digoxin and quinidine can affect patient outcomes.
Purpose of the Study:
- To investigate the effect of quinidine administration on serum digoxin concentrations and renal clearance.
- To determine the clinical implications of the quinidine-digoxin interaction.
Main Methods:
- Observational study involving 79 patients and 5 volunteers.
- Measurement of serum digoxin concentrations before and after quinidine administration.
- Assessment of renal digoxin clearance.
Main Results:
- Quinidine administration resulted in a mean 2.5-fold increase in serum digoxin concentrations (P < 0.001).
- Renal digoxin clearance decreased significantly from 91.6 to 40.6 ml/min (P < 0.001).
- No evidence of digoxin displacement from cardiac binding sites was observed.
Conclusions:
- Concurrent use of quinidine with digoxin leads to significantly elevated digoxin levels.
- A 30-50% reduction in digoxin dosage is suggested when co-administered with quinidine.
- Adverse effects of combined therapy may be attributed to digitalis intoxication.