Draw blood immediately before next scheduled dose. Centrifuge within 2 hours of draw and aliquot to remove serum from spun RBCs.
Specimens that are obtained from gel tubes or anticoagulate collections can cause assay interference.
Flecainide (Tambocor) is a Class I cardiac antiarrhythmic agent indicated for treatment of paroxysmal supraventricular dysrhythmia, paroxysmal atrial fibrillation/flutter, and life-threatening ventricular dysrhythmias. After oral administration, flecainide is nearly completely absorbed and peak concentrations are attained in approximately 3 hours. The half-life averages approximately 20 hours, but is widely variable (12 to 27 hours) and steady-state concentrations are typically achieved in approximately 5 days. Flecainide is eliminated from blood by hepatic metabolism, as well as renal clearance; significant changes in either organ system will cause impaired clearance. Common adverse effects include dizziness, visual disturbances, and dyspnea. Mild-to-moderate toxicity is associated with dizziness, visual disturbances, headache, nausea, fatigue, palpitations, and chest pain. Visual hallucinations and dysarthria may occur at toxic serum concentrations. Death can occur from hypotension, respiratory failure, and asystole.
0.2-1.0 mcg/mL: Therapeutic concentration
>1.0 mcg/mL: Toxic concentration
Flecainide is most effective in premature ventricular contractions suppression at serum concentrations in the range of 0.2 to 1.0 mcg/mL.
Serum concentrations above 1.0 mcg/mL are associated with a high rate of cardiac adverse experiences such as conduction defects or bradycardia.