EMLA
Clinical safety rating: caution
Comprehensive clinical and safety monograph for EMLA (EMLA).
EMLA is a eutectic mixture of lidocaine 2.5% and prilocaine 2.5%. Lidocaine and prilocaine are amide-type local anesthetics that block sodium ion channels in neuronal membranes, inhibiting the initiation and conduction of nerve impulses, thereby producing local analgesia.
| Metabolism | Lidocaine is primarily metabolized by CYP1A2 to monoethylglycinexylidide (MEGX) and further by CYP3A4; prilocaine is metabolized by amidases to o-toluidine metabolites that can oxidize hemoglobin to methemoglobin. |
| Excretion | Lidocaine and prilocaine are metabolized in the liver; lidocaine metabolites (primarily 4-hydroxyxylidine) and prilocaine metabolites (primarily o-toluidine) are excreted renally. Less than 5% of unchanged lidocaine and prilocaine are excreted unchanged in urine. Fecal excretion is negligible. |
| Half-life | After topical application, the terminal elimination half-life of lidocaine is approximately 1.5-2 hours; prilocaine half-life is approximately 1.5 hours. In neonates, half-life may be prolonged due to immature hepatic function. Clinical context: Steady state is achieved within 12-24 hours with repeated application. |
| Protein binding | Lidocaine: 65-70% bound to alpha-1-acid glycoprotein and albumin. Prilocaine: 55% bound to albumin. |
| Volume of Distribution | Lidocaine: Vd approximately 1.0-1.5 L/kg; prilocaine: Vd approximately 1.5-2.0 L/kg. Clinical meaning: Large Vd indicates extensive tissue distribution, including into the CNS and adipose tissue. |
| Bioavailability | Topical bioavailability: 20-30% for lidocaine and prilocaine when applied to intact skin under occlusion; higher (up to 80%) on mucous membranes or abraded skin. Systemic absorption is minimal with recommended doses, but can be significant with prolonged application or large surface areas. |
| Onset of Action | Cutaneous analgesia onset occurs within 1 hour (occlusive dressing) to 2 hours (without occlusion). For dermal analgesia, peak effect at 2-3 hours. Onset is faster on mucosa (e.g., genital, oral) within 5-10 minutes. |
| Duration of Action | Cutaneous analgesia persists for 1-2 hours after removal of the occlusive dressing. On mucosal surfaces, duration is 20-30 minutes. Clinical note: Duration depends on application time; longer application (up to 4 hours) increases depth and duration of anesthesia. |
Apply a thick layer of cream (approximately 2.5 g per 20 cm²) to intact skin under an occlusive dressing for at least 1 hour for minor procedures; for dermal procedures on larger areas, apply up to 60 minutes before procedure, maximum single application area of 600 cm² in adults.
| Dosage form | CREAM |
| Renal impairment | No dose adjustment required for renal impairment; however, use with caution in patients with severe renal impairment due to potential accumulation of lidocaine and prilocaine metabolites. |
| Liver impairment | In Child-Pugh Class B or C, use with caution and consider reduced application area or shorter application time due to reduced metabolism of lidocaine and prilocaine; specific dose modifications not established. |
| Pediatric use | Infants and children: Apply 1-2 g per 10 cm², with maximum application area based on weight: 10 cm² for infants 1-3 months, 20 cm² for 3-12 months, 100 cm² for 1-6 years, 200 cm² for 7-12 years; application time 30-60 minutes depending on age and procedure. |
| Geriatric use | No specific dose adjustment; use with caution in elderly due to increased risk of systemic absorption from thinner skin and potential comorbidities; consider smaller application area or shorter duration. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for EMLA (EMLA).
| Breastfeeding | Lidocaine and prilocaine are excreted into breast milk in low amounts. M/P ratio: lidocaine ~0.4-0.6, prilocaine ~1.0-1.4. Infant dose ~1-2% of maternal weight-adjusted dose. Risk of methemoglobinemia in premature or G6PD-deficient infants. Use with caution. |
| Teratogenic Risk | EMLA (lidocaine 2.5% and prilocaine 2.5%) is FDA Pregnancy Category B. Lidocaine and prilocaine cross the placenta. In first trimester, no increased risk of major malformations in human data. Second and third trimesters: no known fetal harm from topical use. Methemoglobinemia risk in fetus if high doses or prolonged use, especially with prilocaine. |
■ FDA Black Box Warning
EMLA cream can cause methemoglobinemia, especially in children under 12 months, patients with glucose-6-phosphate dehydrogenase deficiency, or those taking oxidizing drugs. Serious and fatal methemoglobinemia has been reported; monitor for signs and symptoms.
| Serious Effects |
Hypersensitivity to lidocaine, prilocaine, or other amide anesthetics; known history of methemoglobinemia; application to eyes or on tympanic membrane; patients with severe hepatic disease (due to impaired metabolism).
| Precautions | Avoid application to open wounds, mucous membranes (except genital), or areas with altered skin barrier. Use with caution in patients with severely traumatized mucosa or sepsis. Monitor for methemoglobinemia, especially in young children. Do not apply to large areas or for prolonged periods. Consider risk of systemic toxicity if applied to inflamed skin or large areas. |
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| Fetal Monitoring | Monitor for signs of local anesthetic toxicity (methemoglobinemia, CNS depression, arrhythmias) in mother. Fetal monitoring: heart rate variability, signs of distress. Methemoglobin levels if high dose or prolonged use. |
| Fertility Effects | No documented effects on fertility in human or animal studies. Lidocaine and prilocaine do not impair reproductive function at therapeutic doses. |