Prilocaine and Emla

General information

Prilocaine is an aminoamide local anesthetic. It can be used on its own, but it is also included in the formulation known as Emla, a eutectic combination of prilocaine with lidocaine (25 mg/ml each), which is used as a local anesthetic in topical administration for, for example, superficial surgery and venepuncture.

Emla cream causes minor local adverse reactions, such as itch, burning, and localized purpura [ , ]. A meta-analysis of the use of Emla cream in elderly people (aged over 65) showed that the technique is generally safe, with only mild transient reactions (pallor, redness, and edema) at the application site; there were no systemic reactions [ ].

However, if large amounts are applied, particularly under occlusion, Emla can be sufficiently well absorbed to cause systemic reactions. Three of 1648 children who received measles vaccination with Emla 1 g had adverse reactions 10–20 minutes later; all required adrenaline for similar symptoms of weakness and dizziness with a cold clammy skin and no pulse or a weak pulse [ ]. One went on to wheeze markedly and had peripheral cyanosis and shivering, improving with hydrocortisone. The authors proposed that these unusual reactions could have been due to a biphasic local reaction to Emla, with vasodilatation leading to increased absorption and further toxicity.

Organs and systems