PHARMACOKINETIC NATURE OF TACHYPHYLAXIS TO LIDOCAINE - PERIPHERAL-NERVE BLOCKS AND INFILTRATION ANESTHESIA IN RATS

Tachyphylaxis to peripheral neural blockade was determined with repeat ed injections of a constant dose of lidocaine in three experimental mo dels: sciatic nerve block, produced by intraneural or extraneural inje ctions, and infiltration anesthesia. A decrease in the duration of the subsequent blocks was used as the index of tachyphylaxis development. The anesthetic content in the nerve or skin was determined using radi olabeled lidocaine. Repeated injections of a constant dose of lidocain e resulted in a marked decrease in the duration of the blocks. Acceler ated decline in lidocaine content of nerve or skin was observed with r epeated blocks. Our data show that tachyphylaxis rapidly develops with both sciatic nerve blocks and infiltration anesthesia. The data also suggest that the mechanism is largely pharmacokinetic in nature. (C) 1 997 Elsevier Science Inc.