Tissue distribution of lidocaine after alveolar infiltration in the rabbit

Objectives:Infiltration anesthesia is widely used for dental treatment. It has been reported that the onset time of local anesthetic action is about 1 - 5 minutes, which is affected by the types and concentration of local anesthetics or vasoconstrictors, and histological structure of the site of administration. However, tissue distribution of local anesthetics after regional injection has been unclear. We used macroautoradiography to visually examine the tissue distribution of lidocaine after alveolar infiltration.

Methods:Male Japan White rabbits (n=24) received an injection of ¹⁴C-labeled 2% lidocaine with or without 1/80,000 epinephrine. We investigated areas of infiltration and proportion of distribution 1, 5 and 10 minute after administration. To determine the proportion of distribution, four sites were selected. A: submucosal tissue of the injection site; B: tissue next to periosteal membrane surrounding alveolar bone (approximately 1/2 of tooth length); C: tissue next to periosteal membrane at the level equivalent to the root apex; D: alveolar bone marrow at the level equivalent to the root apex. Accumulation of ¹⁴C in a circle (13 pixels in diameter) of these sites was measured and the ratio of accumulation in the circles of sites B, C and D to that of site A was compared.

Results:After the administration of 2% lidocaine with 1/80,000 epinephrine, infiltration area increased over time. Ratios of distribution in alveolar bone marrow at the level equivalent to the root apex increased in 1 to 5 minutes after administration, and then decreased. In contrast, after the administration of plain lidocaine, infiltration was hardly detected.

Conclusion:These results suggest that lidocaine with epinephrine infiltrate to wider area over time after administration and then is gradually absorbed into capillaries.