EMLA
EMLA (lidocaine 2.5% + prilocaine 2.5%)
Eutectic mixture of local anesthetics (topical)
Eutectic (lower combined melting point) lidocaine/prilocaine emulsion penetrates intact skin for dermal anesthesia.
Indications
- •Topical skin anesthesia before IV/LP/venipuncture
- •Superficial dermatologic procedures
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| Topical | Apply under occlusive dressing 45–60 min before procedure | — |
Pharmacokinetics
Onset needs ~60 min under occlusion; depth increases with dwell time.
Side effects
- !Methemoglobinemia (prilocaine component — esp. infants, large areas)
- !Skin blanching/erythema
Contraindications
- ×Infants <3 mo / methemoglobinemia risk
- ×Application to broken skin/mucosa (absorption)
Clinical pearls
- ★Needs ~1 h under occlusion — plan ahead for pediatric IV starts.
- ★Prilocaine component → methemoglobinemia risk with large areas/infants.
Other drugs in Local Anesthetics
- Lidocaine
Blocks voltage-gated Na⁺ channels in nerves (LA) and cardiac myocytes (antiarrhythmic).
- Bupivacaine
Voltage-gated Na⁺ channel blocker. Higher protein binding and lipid solubility than lidocaine → longer duration but greater cardiotoxicity.
- Ropivacaine
S-enantiomer of propivacaine. Less lipid-soluble than bupivacaine → less cardiotoxicity but slightly less potency.
- Tetracaine
Blocks voltage-gated Na⁺ channels. Long-acting ester, metabolized by plasma cholinesterase. High potency + toxicity.
- Chloroprocaine
Na⁺-channel blocker. Extremely rapid plasma-cholinesterase metabolism (half-life seconds) → lowest systemic toxicity of the LAs, ideal for OB epidural top-up.
- Procaine
Na⁺-channel blocker; prototype ester LA. Plasma-cholinesterase metabolized to PABA.
- Prilocaine
Na⁺-channel blocker. Metabolized to o-toluidine → oxidizes hemoglobin → methemoglobinemia at high doses.
Suggested reading
- •Stoelting & Hines, Pharmacology & Physiology in Anesthetic Practice, 6e
- •FDA package insert
- •ASRA LAST checklist, 2020
