Effect of repetitive administration of topical local anaesthetic mixture of lidocaine and prilocaine (emla) on non-histaminergic itch

Background and aims: The topical local anesthetic EMLA is a eutectic mixture of lidocaine 2.5% and prilocaine 2.5% often used to anesthetize the skin prior to minor surgical procedures. Recently, we have shown that repetitive administration of EMLA effectively inhibit non-histaminergic itch. In this study we aimed to compare the effect of repetitive short (1H) and long (3H) EMLA administrations on non-histaminergic itch induced by cowhage.

Methods: For three consecutive days, 25mg/g Lidocaine + 25mg/g Prilocaine cream (EMLA) and vehicle cream were topically applied for 1 and 3 hours on each forearm of 25 healthy participants. After cream removal, cowhage (applied by gently rubbing the spicules on the skin) provocation was performed in each area followed by a 9-minute visual analog scale-score (VAS) of itch and pain intensity, measurement of superficial blood perfusion (SBP), alloknesis and hyperknesis.

Results: EMLA reduces itch (p<0.001) and pain (p<0.01) intensities, mean SBP (p<0.05), alloknesis (p<0.01), and hyperknesis (p<0.001) induced by non-histaminergic itch compared to placebo. It was also found a difference between 1H and 3H application at day 1 for both peak itch (p<0.001) and hyperknesis (p<0.05), and during the whole experiment for peak pain (p<0.05). Lastly, the peak itch was lower after 1h application at day 3 compared to day 1 (p<0.01).

Conclusions: EMLA pretreatment reduces cowhage-induced itch, pain, SBP and mechanical sensitivity. Moreover, a higher effect on itch and pain intensity and hyperknesis was elicited by 3 hours application compared to 1 hour.