Influence of Age and Gender on the In Vitro Serum Protein Binding of Flecainide

The in vitro protein binding of flecainide was studied by equilibrium dialysis in relation to serum concentrations of albumin and alpha 1-acid glycoprotein (AAG) in 22 healthy subjects of both sexes aged between 23 and 89 years. In the range of flecainide concentrations tested, protein binding of flecainide was not saturable and the percent value of the unbound fraction ranged between 0.48 and 0.68, mean value (SD)=0.59 (±0.06), without any significant difference between males and females or between young and old subjects. The flecainide unbound fraction was significantly correlated with serum albumin concentrations but not with total serum proteins or AAG concentrations.