Protein binding of prilocaine in human plasma: influence of concentration, pH and temperature.

Protein binding of prilocaine was investigated in vitro under various conditions of changing pH, temperature and total plasma concentration by means of HPLC with UV-detection and ultrafiltration. Whereas changes in temperature (25 degrees C-40 degrees C) and pH (pH 5-pH 10) influenced protein binding markedly, rising plasma concentrations up to 16 micrograms/ml did not affect plasma protein binding significantly. This may be a possible explanation for clinical evidence of low toxicity associated with the use of prilocaine. Discussions concerning protein binding of local anaesthetics should always be based on defined ambient conditions (pH, temperature, concentration).