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The quinidine-digoxin interaction in patients with impaired renal function
International Journal of Clinical Pharmacology, Therapy, and Toxicology
|May 1, 1983
Summary
Quinidine significantly increases serum digoxin concentration (SDC) by reducing its clearance, impacting both renal and non-renal pathways. Careful patient monitoring is essential during coadministration due to high interaction incidence.
Area of Science:
- Pharmacology
- Clinical Pharmacy
- Drug Interactions
Background:
- Digoxin is a critical medication for heart failure and arrhythmias.
- Quinidine is an antiarrhythmic agent with known interactions.
- Previous reports suggest quinidine affects digoxin pharmacokinetics.
Purpose of the Study:
- To investigate the effect of quinidine on serum digoxin concentration (SDC).
- To elucidate the mechanism of digoxin-SCD increase during quinidine coadministration.
- To assess the impact of renal function on this drug interaction.
Main Methods:
- The study analyzed data on SDC in patients coadministered digoxin and quinidine.
- Comparison of SDC changes in patients with normal and impaired renal function.
- Assessment of quinidine's effect on both renal and non-renal digoxin clearance.
Main Results:
- Quinidine significantly increases SDC during coadministration.
- This increase is primarily due to reduced digoxin clearance, affecting both renal and non-renal pathways.
- The interaction's magnitude is similar in patients with varying degrees of renal impairment.
- Quinidine does not affect digoxin's plasma protein binding.
Conclusions:
- Quinidine-induced reduction in digoxin clearance is the primary mechanism for increased SDC.
- Non-renal clearance of digoxin is significantly reduced by quinidine.
- Close monitoring of digitalized patients is crucial when initiating quinidine therapy.
- Extended monitoring is necessary for patients with impaired renal function due to delayed steady-state SDC.