title: Analysis of nonlinear tissue distribution of quinidine in rats by physiologically based pharmacokinetics.
abstract: The nonlinear tissue distribution of quinidine in rats was investigated by a physiologically based pharmacokinetic model. Serum protein binding of quinidine showed a nonlinearity over the in vivo plasma concentration range. The blood-to-plasma concentration ratio (Cb/Cp) of quinidine also showed a concentration dependence. The steady-state volume of distribution (Vss) determined over the plasma concentration range from 0.5 to 10 micrograms/ml was 6.0 +/- 0.45 L/kg. The tissue-to-plasma partition coefficient (Kp) of muscle, skin, liver, lung, and gastrointestinal tract (GI) showed a nonlinearity over the in vivo plasma concentration range of quinidine, suggesting saturable tissue binding. The concentration of quinidine in several tissues and plasma was predicted by a physiologically based pharmacokinetic model using in vitro plasma protein binding and the Cb/Cp of quinidine. The tissue binding parameters were estimated from in vivo Kp values. The predicted concentration curves of quinidine in each tissue and in plasma showed good agreement with the observed values.
mesh_terms: D000818:Animals; D007700:Kinetics; D008954:Models, Biological; D011485:Protein Binding; D011802:Quinidine / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D014018:Tissue Distribution
chemical_list: D011802:Quinidine