ION-PAIRING OF DYCLONINE WITH DYES

This potential for ion-pairing between dyclonine, a local anesthetic, and pharmaceutical dyes commonly used in liquid pharmaceutical formula tions was examined. Occurrence of ion-pairing at a pH of 3 was confirm ed by shift of the absorption maximum of all five sulfonate-containing dyes, and by measurements of octanol/water partition coefficient and surface tension. There was also an increase in the uptake of dyclonine by phosphatidylcholine liposomes in the presence of a dye (tartrazine ) at pH 3 but not at pH 7, where the uncharged anesthetic is dominant.