​EMLA Cream Ingredients – Formulation Overview​

Lidocaine and prilocaine are two of the most popular agents in topical anesthetics. Many praise them for their effectiveness and favorable safety profiles. These ingredients work by temporarily blocking nerve signals in the skin, making them ideal for localized pain relief during various medical and cosmetic procedures.

One topical anesthetic that combines both ingredients is EMLA cream. Specifically designed for use in clinical and outpatient settings, its balanced formulation optimizes skin penetration and minimizes irritation, providing a reliable option for safe and effective anesthesia.

This article will explore the ingredients in EMLA cream, how they work synergistically, and what sets this formulation apart in the field of topical anesthetic applications.

Key Takeaways

• EMLA cream combines 2.5% lidocaine and 2.5% prilocaine, both amide-type anesthetics that block nerve signals to provide effective localized pain relief.
• The ingredients form a eutectic mixture, which remains liquid at room temperature, enhancing skin penetration and delivering deeper anesthetic action.
• Excipients like Carbomer 974P, macrogolglycerol hydroxystearate, sodium hydroxide, and purified water support the cream’s stability, consistency, and absorption.
• The cream’s oil-in-water emulsion and pH-adjusted formulation contribute to clinical reliability, especially when used with an occlusive dressing.
• Proper application time (typically 45–60 minutes) and technique are essential for achieving the full anesthetic effect with minimal risk.

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Roles of Lidocaine and Prilocaine in Anesthesia

EMLA cream’s numbing capability comes from its two active ingredients: lidocaine and prilocaine, each present at 2.5% concentration (25 mg per gram). Both are amide-type local anesthetics that work by blocking sodium channels in nerve membranes, preventing the transmission of pain signals. This creates a localized anesthetic effect, allowing for more comfortable minor procedures.

The combination of these two agents provides a broader and more sustained anesthetic coverage. Lidocaine acts quickly, offering a rapid onset, while prilocaine has a slightly longer duration of action, enhancing the cream’s usefulness for both short and prolonged interventions. Their synergy makes EMLA suitable for dermatological treatments, minor surgeries, and cosmetic applications.

Excipients and Their Contribution to Efficacy

In addition to its active components, EMLA cream contains several inactive ingredients (excipients) that are critical to its performance and stability:

• Macrogolglycerol Hydroxystearate: Functions as an emulsifier, keeping the cream’s oil and water phases uniformly mixed.
• Carbomer 974P: A thickening agent that gives the cream its application-friendly consistency.
• Sodium Hydroxide: Adjusts the pH level of the cream to improve skin absorption and maintain the stability of lidocaine and prilocaine.
• Purified Water: Acts as the solvent base, allowing even distribution of ingredients.

Together, these excipients help the cream spread uniformly, stay stable during storage, and enhance transdermal absorption, supporting a consistent anesthetic effect across applications.

Eutectic Mixture Ratio and Drug Delivery Mechanisms

One of the most distinctive features of EMLA is its eutectic mixture of equal parts lidocaine and prilocaine. Individually, both are solid at room temperature, but together they form a liquid oil due to their lowered melting point when combined.

This eutectic formulation allows the anesthetics to remain in liquid form, enhancing their ability to penetrate the skin barrier and reach deeper dermal layers. This characteristic is especially important in procedures requiring deep dermal anesthesia. It also provides a useful contrast in formulation strategy when comparing EMLA vs LET, where EMLA is preferred for intact skin, and LET is often used on open wounds due to faster onset and direct tissue exposure.

Physicochemical Properties and Clinical Implications

EMLA cream’s physicochemical attributes contribute significantly to its clinical performance. Its oil-in-water emulsion allows for easy application and uniform coverage on the skin. The cream is pH-adjusted to enhance ingredient stability and maximize absorption across the epidermal and dermal layers.

Clinically, occlusion (using a dressing) is vital to optimizing EMLA’s efficacy. Occlusion traps moisture, increases skin permeability, and ensures the cream remains in place. For most procedures, it is recommended that the cream be applied for 45 to 60 minutes under an occlusive dressing. The numbing effect typically lasts for 1 to 2 hours after removal, making it ideal for dermatological and outpatient procedures.

Formulation Stability and Penetration Factors

The stability and delivery effectiveness of EMLA cream stem from its carefully designed formulation. The emulsifiers and stabilizers prevent ingredient separation and maintain the cream’s homogeneity throughout its shelf life. To ensure longevity and continued effectiveness, practitioners should store it at room temperature, away from direct sunlight.

The extent and speed of penetration are influenced by:

• Skin thickness (e.g., thinner skin absorbs faster),
• Application duration (longer exposure = deeper anesthesia),
• Use of occlusion (increases skin hydration and drug diffusion).

Following manufacturer guidelines ensures the anesthetics reach their target depth and provide the desired effect—whether for laser procedures, biopsies, or injections.

Conclusion

EMLA cream’s formulation—an equal-parts eutectic mix of lidocaine and prilocaine—makes it a powerful and dependable choice for topical anesthesia. Its combination of active agents, stabilizing excipients, and a delivery system designed for enhanced absorption positions it as a go-to for non-invasive pain relief. When properly applied, it provides deep, localized numbness suitable for a wide range of medical and cosmetic uses.

Understanding EMLA’s mechanism of action, supporting components, and clinical application strategies is essential for optimizing its effectiveness and safety in practice.

FAQs

1. What are the active ingredients in EMLA cream?

EMLA cream contains two active ingredients: lidocaine (2.5%) and prilocaine (2.5%). These local anesthetics work together to numb the skin by blocking nerve signals. 

2. How does the eutectic mixture enhance EMLA’s effectiveness?

The eutectic mixture of lidocaine and prilocaine lowers their melting points, resulting in a liquid form at room temperature. This enhances skin penetration, allowing the anesthetics to reach deeper layers for effective numbing.​

3. How long should EMLA cream be applied before a procedure?

EMLA cream should be applied under an occlusive dressing for optimal anesthesia 45 to 60 minutes before the procedure. This allows sufficient time for the anesthetics to penetrate the skin.

4. What procedures do practitioners use EMLA cream for?

EMLA cream numbs the skin for minor surgical procedures, IV insertions, blood draws, and certain cosmetic treatments.

5. How long does the numbing effect last after application?

Depending on the duration of application, the numbing effect typically lasts 1–2 hours after removing the cream.

6. Can I apply EMLA cream on broken or irritated skin?

No, do not apply EMLA on broken or irritated skin, as it may increase absorption and the risk of side effects.

7. How should EMLA cream be stored?

EMLA cream should be stored at room temperature away from moisture, heat, and direct sunlight. It should not be allowed to freeze.

References

Weilbach C, Hoppe C, Karst M, et al. Effectiveness of various formulations of local anesthetics and additives for topical anesthesia – a prospective, randomized, double-blind, placebo-controlled study. Journal of Pain Research. 2017;Volume 10:1105-1109. doi:10.2147/jpr.s131029

EMLA (Lidocaine and prilocaine): side effects, uses, dosage, interactions, warnings. RxList. https://www.rxlist.com/emla-drug.htm

EMLA: Package insert / Prescribing information. Drugs.com. https://www.drugs.com/pro/emla.html