The Addition of Epinephrine to Proxymetacaine or Oxybuprocaine Solution Increases the Depth and Duration of Cutaneous Analgesia in Rats.

Background: The aim of this experiment was to investigate the interaction between epinephrine and 2 local anesthetics (proxymetacaine or oxybuprocaine) using subcutaneous injections under the hairy skin, thereby simulating infiltration blocks. Methods: Using a rat model of cutaneous trunci muscle reflex in response to local skin pinpricks, the anesthetic properties of proxymetacaine and oxybuprocaine alone and in combination with epinephrine as an infiltrative anesthetic were tested. Isobolographic analysis was used for the analgesic interactions between adjuvant epinephrine and the local anesthetics. Lidocaine was used as a control group. Results: Oxybuprocaine, proxymetacaine, and lidocaine elicited a dose-dependent block to pinpricks. On the 50% effective dose (ED50) basis, their relative potencies were proxymetacaine [0.126 (0.113-0.141) [mu]mol] greater than oxybuprocaine [0.208 (0.192-0.226) [mu]mol] greater than lidocaine [6.331 (5.662-7.079) [mu]mol] (P

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