The local anesthetic effect of tetracaine in polylactic acid microspheres was compared with that of tetracaine hydrochloride solutions. As a first step, the local anesthetic effect of 0.1 ml tetracaine hydrochloride solutions was examined at four concentrations in vivo. Then, the local anesthetic effect of 0.2 ml tetracaine hydrochloride solutions was compared with that of 0.1 ml tetracaine hydrochloride solutions. The more the amount of tetracaine, the stronger and longer was the local anesthetic effect. The local anesthetic effect of tetracaine in microspheres was much longer and lasted over 100 h.
Anesthetics, Local Animals