Localization of 14C-Labeled 2% Lidocaine Hydrochloride after Intraosseous Anesthesia in the Rabbit

ObjectiveThe purpose of this study was to investigate the tissue distribution of lidocaine hydrochloride in mandibular bone marrow after intraosseous anesthesia (IOA) in rabbits.MethodsWe used macroautoradiography to examine the tissue distribution of a 14C-labeled 2% lidocaine hydrochloride solution containing 1:80,000 epinephrine (14C-lidocaine). Under general anesthesia, 14C-lidocaine was injected intraosseously or paraperiosteally. After IOA, animals were divided into three groups and observed at 1 (IOA-1), 5 (IOA-5), and 10 minutes (IOA-10) after injection. After infiltration anesthesia (IA), animals were observed at 1 minute after injection.ResultsThe accumulation of 14C-lidocaine was observed around the injection site in both the IA and the IOA groups. Paraperiosteally injected 14C-lidocaine diffused to the surrounding tissues such as the lip, whereas IOA showed concentrated accumulation around the root apex throughout the experiment. The distribution area was significantly smaller in the IOA-1 group than in the IA group. The distribution area in the IOA-5 group was larger than those in the IOA-1 and IOA-10 groups.ConclusionsThe accumulation of 14C-lidocaine injected by IOA in rabbits was concentrated around the root apex. These results may explain the rapid onset time of IOA.