The secretion of propranolol enantiomers in human saliva: evidence for active transport?

To study the possible transport routes which may lead to the presence of a drug in saliva, the concentration-time curves of the separate enantiomers of propranolol were measured in human saliva and plasma after oral administration of 10 mg of propranolol hydrochloride. Saliva samples were taken with the Salivette device. Plasma and saliva concentrations of the enantiomers of propranolol were determined by HPLC with fluorescence detection. The transport of propranolol from plasma to the salivary gland appears to be not stereospecific and not saturable. Therefore, there is no indication that the transport of propranolol to the salivary gland is active. The concentrations of both enantiomers of propranolol in saliva, however, were higher than those of both enantiomers in venous plasma. In the past this phenomenon was interpreted as an indication of active transport, but it could be explained by the fact that salivary concentration more closely reflects the central compartment than that of peripheral venous blood.