Topical anaesthesia with EMLA, a new lidocaine-prilocaine cream and the Cusum technique for detection of minimal application time.

The minimal effective onset time of the new topical anaesthetic formulation EMLA (a eutectic mixture of lidocaine and prilocaine), was evaluated by the double-blind technique in 53 female and 66 male patients (median age 40 and 36 years, respectively) subjected to intravenous cannulation. Conventional plotting and regression analysis failed to answer the question. The Cusum technique, originally designed for industrial production control, could successfully be applied to solve the problem. It demonstrated a minimal effective EMLA application time of 45 min in adults.