On the distribution of drugs in saliva and blood plasma

The equilibration of drug concentrations between blood plasma (unbound part) and saliva was studied for selected drugs with different physicochemical properties: Quinidine, sulfamerazine, paracetamol, diazepam and ethanol. From these and other experimental results it is suggested: 1. The concentration ratio between saliva and blood plasma (unbound) can only equal one for basic drugs with a pK a lower than 5.5 and acid drugs with a pK a higher than 8.5 and for pH indifferent drugs. 2. The drug must have a sufficient permeation ability through lipid membranes, valuable by the lipid water partition coefficient.