BACKGROUNDWe have synthesized a sustained-releaselidocaine sheet (SRLS) and injectable sustained-release lidocaine particles(SRLP) using biodegradable polymers. In the present study, we performed anexploratory first clinical trial of the SRLS in healthy volunteers as a preludeto patient administration. This trial is meant as an initial intervention inultimately developing and refining the SRLP. METHODSWe evaluated the intensity and duration ofanalgesia of the SRLS compared with 8% lidocaine spray. In Protocol 1, weapplied the SRLS piece to the mucous membrane of the nasal vestibule. Weexamined the local pain threshold over 72 h after administration, and removedthe SRLS after 72 h. Individuals that finished Protocol 1 underwent Protocol 2,in which we applied 8% lidocaine spray. RESULTSTwelve volunteers were enrolled and seven ofthese volunteers finished Protocol 1. All seven individuals who completedProtocol 1 also completed Protocol 2. The mean pain thresholds were 32 g, 78 g,90 g, 90 g, 87 g, and 87 g at pre-administration and 4 h, 10 h, 24 h, 48 h, and72 h after administration, respectively, in Protocol 1, and 36 g, 85 g, 49 g,and 33 g at pre-administration and 15 min, 2 h, and 4 h, respectively, inProtocol 2. CONCLUSIONA sustained-release lidocaine usingbiodegradable polymers was applied as a sheet in humans for the first time inthe world. It maintained significant analgesia for 72 h without majortoxicities. Furthermore, degree of analgesia provided by the SRLS throughoutthe entire study was similar to that provided by the 8% lidocaine spray. It may suitable for management ofpostoperative pain especially in outpatients
