title: Quinidine saliva concentrations: absence of correlation with serum concentrations at steady state.
abstract: Serum and saliva quinidine concentrations were measured in eight subjects with cardiac arrhythmias on various dosage regimens. There was good correlation between serum and saliva quinidine concentration after a single dose, but there was no such relationship after repeated dosing. Comparison of the area under a hysteresis loop, obtained by plotting the saliva/serum quinidine concentration ratio as a function of serum quinidine concentration over a dosing interval, indicated an exponential increase with increasing mean serum quinidine concentration. Salivary quinidine concentration predictions based on the Henderson-Hasselbalch equation did not correlate with the serum quinidine concentration under the steady-state conditions. These data suggest that quinidine concentration in saliva is not a direct reflection of its serum concentration in cardiac patients on maintenance (steady-state) therapy and hence not useful for therapeutic drug monitoring.
mesh_terms: D000284:Administration, Oral; D000368:Aged; D001145:Arrhythmias, Cardiac / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D011802:Quinidine / Q000097:blood / Q000378:metabolism*; D012463:Saliva / Q000032:analysis*
chemical_list: D011802:Quinidine