EMLA (Eutectic Mixture of Local Anesthetics)

What It Is

EMLA cream is a topical analgesic containing 2.5% lidocaine + 2.5% prilocaine. The term "eutectic" refers to the fact that combining these two amide local anesthetics lowers the melting point of the mixture, forming an oil at room temperature that penetrates the keratinized skin barrier - something neither agent alone can do effectively. - Katzung's Basic and Clinical Pharmacology, p. 736

Indications

Intact skin prior to venipuncture, IV catheter insertion, lumbar puncture, minor dermatological procedures, skin grafting
Genital mucous membranes for superficial minor surgery (e.g., condylomata removal) and as pretreatment before infiltration anesthesia
Pediatrics - particularly common for venipuncture and IM injections in children - Tintinalli's Emergency Medicine, p. (TOPICAL ANESTHESIA section)

How to Apply

Apply a thick layer to intact skin
Cover with an occlusive (airtight) dressing (e.g., Tegaderm or plastic wrap)
Leave on for at least 60 minutes (up to 2-5 hours for deeper or more painful procedures)
Wipe off immediately before the procedure

When applied for at least 60 minutes under an occlusive dressing, EMLA is as efficacious as local anesthetic infiltration for venipuncture and many dermal procedures. - Tintinalli's Emergency Medicine

Dosing by Age/Weight

(From the Harriet Lane Handbook, 23rd ed.)

Patient	Dose	Max Area	Max Time
Preterm (<37 wk)	0.5 g/site	-	60 min
Term neonate (<5 kg)	1 g/site	10 cm²	1 hr
3-12 mo, >5-10 kg	up to 2 g	20 cm²	4 hr
1-6 yr, >10 kg	up to 10 g	100 cm²	4 hr
7-12 yr, >20 kg	up to 20 g	200 cm²	4 hr
Adults (minor)	2.5 g/site over 20-25 cm²	-	60 min min
Adults (max)	60 g total	-	5 hr

Contraindications / Cautions

Do NOT apply to open wounds, damaged skin, or near the ear canal (risk of ototoxicity if it reaches the middle ear)
Methemoglobinemia risk - prilocaine is metabolized to ortho-toluidine, which oxidizes hemoglobin; caution in:
- Infants <3 months (limited methemoglobin reductase activity)
- Patients on oxidizing drugs (dapsone, nitrates, sulfonamides)
- G6PD deficiency
Use with caution in acutely ill, debilitated, or elderly patients (greater systemic absorption risk)
Avoid in patients with known amide local anesthetic hypersensitivity

Onset & Duration

Onset: 45-60 min under occlusion (earlier for mucous membranes)
Duration of analgesia after removal: 1-2 hours
Depth of analgesia: ~3 mm at 60 min; ~5 mm at 90+ min

Formulations

Cream (EMLA): 2.5% lidocaine + 2.5% prilocaine (5 g and 30 g tubes)
Periodontal gel (Oraqix): same concentrations, in 1.7 g dental cartridges

Key Takeaways

First topical anesthetic formulated to penetrate intact skin (due to the eutectic formulation)
Highly effective for needle-phobic patients, especially children
Must be applied under occlusion well in advance - rushed application (< 45 min) reduces efficacy significantly
Do not exceed recommended doses, particularly in infants, due to methemoglobinemia risk

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