Effect of epinephrine on the distribution of ropivacaine and lidocaine using radioactive isotopes in rat maxilla and pulp.

We compared the effect of epinephrine on the distribution of ropivacaine and lidocaine by using radioactive isotopes in rat maxilla and pulp. Twenty microliters of 3H-labeled 0.5% ropivacaine, 14C-labeled 2.0% lidocaine, or epinephrine-supplemented isotopes were injected into the maxilla. The radioactivity was measured and autoradiography was obtained. Epinephrine led to increase in amounts of both anesthetics in the maxilla and pulp; however, each anesthetic did so in a different manner. Addition of epinephrine to lidocaine decreased radioactivity in maxilla and pulp with time. Conversely, when ropivacaine with epinephrine was administered, radioactivity did not change until 20 min in the maxilla and reached its peak at 20 min in the pulp. Autoradiography of lidocaine faded with time even with epinephrine use; however, with ropivacaine, higher accumulation image was observed after 20 min compared to that after 2 min. When epinephrine was combined with lidocaine, the amount of lidocaine in maxilla and pulp decreased with time, similar to when lidocaine was used alone. Conversely, when ropivacaine-epinephrine combination was administered, the amount of ropivacaine remained unchanged for 20 min in the maxilla and reached its peak at 20 min in the dental pulp.