Metabolism of flecainide.

Area of Science:

• Pharmacology
• Clinical Pharmacy
• Drug Metabolism

Background:

• Flecainide is an antiarrhythmic drug used to treat cardiac arrhythmias.
• Understanding its pharmacokinetic profile is crucial for safe and effective therapeutic use.

Purpose of the Study:

• To characterize the oral absorption, distribution, metabolism, and excretion (ADME) of flecainide in healthy subjects and patients with specific conditions.
• To identify factors influencing flecainide pharmacokinetics, such as renal function and congestive heart failure (CHF).

Main Methods:

• Oral administration of flecainide in healthy human subjects and patients with cardiac arrhythmias, renal disease, and CHF.
• Measurement of plasma flecainide levels, half-life, and urinary excretion of unchanged drug and metabolites.
• Assessment of flecainide protein binding and the impact of food, antacids, and urinary pH.

Main Results:

• Flecainide exhibits prompt and nearly complete oral absorption (≥90%), unaffected by food or antacids.
• Plasma levels are proportional to dose, with a relatively long half-life (mean 13-16 hours in healthy subjects, longer in patients with ventricular premature complexes).
• Elimination is primarily via urine (86%), with reduced clearance in patients with moderate to end-stage renal disease and CHF; dosage reduction is recommended in these populations.

Conclusions:

• Flecainide's pharmacokinetic profile is generally predictable and linear within the therapeutic range.
• Renal function significantly impacts flecainide elimination, necessitating dose adjustments in patients with impaired renal function.
• While metabolites are present, they possess minimal antiarrhythmic activity, with unchanged flecainide being the primary active compound.