By Gary M. White, MD
Note: This is a summary only. Please consult the latest information when prescribing.
Topical anesthetics are effective for reducing pain in patients undergoing superficial dermatological and laser procedures. Usually, the product is applied under occlusion to the area to be treated 1 hour before the procedure.
EMLA (eutectic mixture of 2.5% lidocaine and 2.5% prilocaine) is applied to the skin, then covered with an occlusive dressing and left in place for at least 60 minutes. The duration of anesthesia is on average 1-3 hours.
Side effects include skin irritation, vasoconstriction, and (later) vasodilatation. Extremely rare systemic reactions have occurred in patients with known allergy to lidocaine. The development of methemoglobinaemia is a rare but known complication of prilocaine. EMLA should be used with caution in neonates (especially premature infants), those with glucose-6-phosphate deficiency, or with medication known to exacerbate methemoglobinaemia and congenital methemoglobinaemia.
Ametop has a more rapid onset of action (e.g., 30-45 minutes) and a longer duration of anesthesia (4-6 hours) but is more expensive.
Side effects include local erythema.
LMX4® (previously known as ELA-Max) is an OTC topical anesthetic containing 4% lidocaine in a gel vehicle. It provides effective analgesia after 30 minutes of application and produces minimal skin changes as compared to the other topical anesthetics. The recommended application time for LMX4® is 60 minutes. No occlusion is required.