IN VITRO AND IN SITU TRANSFER OF LOCAL ANAESTHETICS ACROSS ORAL MUCOSA

The rates of transfer of C14-labelled lidocaine and prilocaine through the frenulum of the tongue of the dog were studied in vitro and in situ. Tenfold increases of the local anaesthetic concentration on the outside of the frenulum increased the rate the radioactivity was transferred to the inside by tenfold in the in vitro preparation. In situ, a doubling of the local anaesthetic concentration resulted in a greater than twofold increase in transfer rate. The transfer of local anaesthetic both in vitro and in situ increased as the pH of the applied local anaesthetic solution increased. Incorporation of 1 per cent cetylpyridinium chloride into the local anaesthetic solution in vitro could either increase or decrease the transfer of local anaesthetic. When 0.1 or 0.01 per cent cetylpyridinium chloride was added to the local anaesthetic solution in situ, the rate of local anaesthetic transfer was increased. The similarity between transfer of local anaesthetics across the frenulum of the tongue and transfer across lipoid membrane is discussed. © 1969.