Interaction of flecainide with digoxin and propranolol

Area of Science:

• Pharmacology
• Clinical Pharmacy

Background:

• Digoxin is a cardiac glycoside used to treat heart failure and arrhythmias.
• Flecainide is a Class Ic antiarrhythmic drug.
• Interactions between antiarrhythmic drugs and digoxin can alter drug efficacy and safety.

Purpose of the Study:

• To investigate the effect of flecainide on steady-state plasma digoxin levels.
• To assess the combined effects of flecainide and propranolol on cardiovascular parameters.

Main Methods:

• 15 healthy males received digoxin (0.25 mg/day) with or without flecainide (200 mg BID).
• Plasma digoxin levels were measured predose and 6-hour postdose.
• 10 healthy males received propranolol (80 mg TID) or flecainide alone or in combination, with various cardiovascular parameters monitored.

Main Results:

• Flecainide co-administration led to a significant increase in predose (p<0.05) and 6-hour postdose (p<0.05) digoxin levels.
• Average increases in predose and postdose digoxin levels were 24% and 13%, respectively.
• Flecainide and propranolol showed additive effects on blood pressure reduction.

Conclusions:

• Flecainide significantly increases plasma digoxin concentrations.
• Concurrent use of flecainide and digoxin may require digoxin dose adjustment.
• Combined administration of flecainide and propranolol results in additive blood pressure lowering effects.