In-vitro plasma protein binding of propafenone and protein profile in eight mammalian species

The protein binding of propafenone in vitro was assessed in plasma of mouse, rat, rabbit, dog, sheep, man, cow, and horse at two concentration levels. In all species and at both concentrations propafenone was found highly bound (86-99%) to plasma proteins. No significant relationship was found between free propafenone and the plasma protein fractions. A concentration-dependency was seen in plasma of mouse, sheep, man, and horse, in which the free fraction of propafenone became larger on raising the concentration. Qualitative and quantitative differences were observed in the protein plasma profile of studied species. The protein plasma profile and propafenone concentration may affect the free fraction of the drug to different extents in different species. Thus the pharmacological activity of propafenone may be different in different species even at the same propafenone plasma concentration.