Emla Mechanism of Action

Pharmacotherapeutic Group: Local anaesthetics of the amide type. ATC Code: N01BB20.
Pharmacology: Pharmacodynamics: Emla cream contains lidocaine and prilocaine, which are local anaesthetics of the amide type. On penetration into the epidermis and dermis, these substances produce dermal anaesthesia. The degree of anaesthesia depends on application time and dose.
Intact Skin: With an application time of 1-2 hrs, the effect lasts for approximately 2 hrs after the occlusive dressing has been removed.
In clinical studies of Emla on intact skin, no differences in safety or efficacy (including anaesthetic onset time) were observed between geriatric patients (aged 65-96 years) and younger patients.
The superficial vascular bed is affected by Emla and this can cause transient paleness or redness. These reactions appear to occur more rapidly in atopic dermatitis, after only 30-60 min, indicating more rapid absorption through the skin (see also Precautions).
A study in healthy volunteers with intact skin shows that in 90%, the anaesthesia is sufficient for use of biopsy punch (4 mm in diameter) to an insertion depth of 2 mm, following 60 min application time and to a depth of 3 mm following 120 min application time.
The effectiveness of Emla is independent of the colour of the skin/pigmentation of the skin (skin types I-IV).
Emla can be used prior to vaccination with SC or IM vaccine. For intracutaneous vaccination with live vaccine eg, BCG, see Warnings and Precautions.
Genital Mucosa: The time to onset of the necessary anaesthesia is shorter, as absorption is more rapid than with application to intact skin.
Following 5-10 min application of Emla to the genital mucosa in women, the anaesthetic effect against argon laser-induced pain lasted for 15-20 min (with an interindividual variation from 5-45 min).
Leg Ulcers: No negative effect on ulcer healing or bacterial flora has been observed. When cleaning leg ulcers, Emla has analgesic effect for up to 4 hrs after application.
Pharmacokinetics: The systemic absorption of Emla depends on the amount of cream, application time, thickness of the skin (which varies on different surfaces of the body) and condition of the skin in other respects such as skin diseases (eg, absorption increases in atopic dermatitis, see Warnings and Precautions) and shaving. When used on leg ulcers, the characteristics of the leg ulcer can affect absorption, eg, absorption increases with increased size of the leg ulcer.
Intact Skin: After application of Emla cream 60 g/400 cm² (1.5 g/10 cm²) for 3 hrs to intact skin (the thigh) in adults, systemic absorption was measured as 3% for lidocaine and 5% for prilocaine. Absorption takes place slowly. With the previously mentioned dose, peak plasma concentrations for lidocaine (mean 0.12 mcg/mL) and prilocaine (mean 0.07 mcg/mL) were reached within approximately 4 hrs after application. Only at levels of 5-10 mcg/mL are there risks of toxic symptoms. In this case, shaving of the skin took place 8-12 hrs before application of the cream.
Plasma levels of lidocaine and prilocaine in both geriatric and non-geriatric patients following application of Emla to intact skin are very low and well below potentially toxic levels.
Leg Ulcers: After application to leg ulcers of Emla 5-10 g for 30 min, peak plasma levels of lidocaine and prilocaine were reached after approximately 1-2.5 hrs (for lidocaine within the range 0.05-0.84 mcg/mL and for prilocaine 0.02-0.8 mcg/mL).
Following repeated application of Emla to leg ulcers, there was no apparent accumulation in plasma of lidocaine, prilocaine or their metabolites. Emla 2-10 g was applied for 30-60 min to a maximal surface of 62 cm², in total 15 times during a period of 1 month, 3-7 sessions a week.
Genital Mucosa: After application of Emla 10 g cream to vaginal mucosa for 10 min, peak plasma concentrations were measured after approximately 35 min (mean values: Lidocaine 0.18 mcg/mL, prilocaine 0.15 mcg/mL).