 Steady-state procainamide and acecainide concentrations were used to compute procainamide clearance and acecainide/procainamide (NAPA/PA) concentration ratio.Using stepwise multiple linear regression age, creatinine clearance and congestive heart failure were found to influence procainamide clearance significantly (p less than 0.05).Age and creatinine clearance effected the NAPA/PA concentration ratio (p less than 0.05).