Plasma concentrations of prilocaine and lidocaine and methaemoglobin formation in infants after epicutaneous application of a 5% lidocaine-prilocaine (EMLA).

The aim of the study was to measure the plasma levels of lidocaine and prilocaine after dermal application of EMLA in infants and to evaluate whether this procedure increases the levels of methaemoglobin (Met-Hb). Two groups of infants, 3-6 (n = 12) and 6-12 months (n = 10) of age, were studied. In total, 2 ml of EMLA was applied to 4 x 4 cm of skin surface for 4 h and blood samples for detection of Met-Hb and plasma levels of local anaesthetics were taken at 0, 2, 4 and 8 h after the application. After removal of the cream the infants were operated mainly for minor procedures under general anaesthesia. The plasma concentrations of lidocaine and prilocaine were in all cases below toxic levels and there were only minor increases in Met-Hb in a few infants. In conclusion, EMLA can be used safely in infants above 3 months of age provided that the recommendations with regard to dose, application area and time are followed. The use of EMLA in smaller infants and in children taking other Met-Hb-inducing drugs needs further evaluation.