EMLA anaesthetic cream for debridement of burns: a study of plasma concentrations of lidocaine and prilocaine and a review of the literature

摘要

The lidocaine-prilocaine cream (EMLATM) effectively reduces the pain from debridement of chronic leg ulcers. Studies have demonstrated that when applied to leg ulcers, plasma concentrations of the local anaesthetics are well below the threshold for CNS toxicity. However, there are minimal pharmacokinetic data available from EMLA application to burn wounds. This study evaluated EMLA cream for debridement of burns with regard to plasma concentrations of lidocaine and prilocaine, and reviewed the published literature on safety and efficacy of lidocaine-prilocaine applied epicutaneously to burns. Eight patients aged 22-59 received 5 g of EMLA 5% cream applied to 25 cm2 large 2nd degree burn areas for 30 min. Venous blood samples drawn at set intervals up to 120 min after cream application were analyzed for total plasma concentrations of lidocaine and prilocaine. Pain from debridement was assessed on a 4-point verbal scale and a 100-mm visual analog scale (VAS) with the end points “no pain” and “severe pain”. A literature search on the use of lidocaine-prilocaine cream on burn wounds was performed in PubMed. The results showed that six patients felt no pain and two patients mild pain. The median VAS score was 11 (range 2-59). Peak plasma concentrations of lidocaine (mean 205 ng/ml) and prilocaine (mean 97 ng/ml) were observed after 15-60 min. Two published studies and two case reports of overdose of lidocaine-prilocaine cream applied to burns in paediatric patients were retrieved. Peak plasma concentrations of lidocaine and prilocaine combined after application of 5 g EMLA to burns 25 cm2 large for 30 min in adults are far below those associated with toxicity. Bioavailability estimation suggests 5 to 30% of the prilocaine dose applied to burns is percutaneously absorbed. The analgesic efficacy appears satisfactory for debridement of 2nd degree burns.