Background: Although the lignocaine (lidocaine)-prilocaine cream EMLA has been extensively studied for the relief of acute treatment-related pain from sharp leg ulcer debridement, no data exist on systemic absorption from prolonged application in patients with chronically painful ulcers.
Objectives: To study the plasma concentrations of lignocaine and prilocaine resulting from prolonged application of EMLA to leg ulcers.
Methods: A single 24-h application of 5-10 g (median 6.75) of EMLA was given to 10 patients with painful leg ulcers measuring 50-100 cm2. Venous blood samples, drawn between 0.5 and 27 h after cream application, were analysed by gas chromatography using a nitrogen-sensitive detector.
Results: The peak plasma levels were in the range 185-705 ng mL(-1) and 62-277 ng mL(-1) for lignocaine and prilocaine, respectively, and were observed 2-4 h (in one patient 6-8 h) after application. The peak plasma concentration of lignocaine, but not of prilocaine, increased significantly with increasing dose. The cream was well tolerated by the patients.
Conclusions: The results indicate that a 24-h application of 5-10 g EMLA results in peak plasma concentrations of the two local anaesthetics, which combined are less than one-fifth of those associated with toxic reactions. The analgesic efficacy of EMLA for the relief of chronic ulcer pain deserves further study.