Question 1

Can I leave Emla Cream on for longer than 2 hours to make it work better?

Accepted Answer

Leaving Emla Cream on for longer than 2 hours is not recommended for routine use and provides diminishing returns for anaesthetic depth while increasing safety risks. While extended application up to 5 hours is used in specific medical settings (like split-skin grafting under supervision), for most applications 90-120 minutes provides maximum anaesthetic effect. Beyond this time, the stratum corneum becomes fully saturated and additional drug penetration is minimal. However, systemic absorption continues gradually, increasing the risk of side effects without significant clinical benefit. The only exceptions are specific medical procedures where deeper anaesthesia is needed, and these should only be performed under medical supervision. For standard uses like blood tests or injections, 60-90 minutes application provides optimal results with maximum safety.

Question 2

Why does the numbing effect last longer than the time the cream is applied?

Accepted Answer

The prolonged effect occurs because the stratum corneum (outer skin layer) acts as a drug reservoir that continues releasing anaesthetics after cream removal. During application, lidocaine and prilocaine accumulate in the lipid-rich stratum corneum, creating a depot effect. After removal, these stored drugs gradually diffuse into deeper skin layers, maintaining anaesthetic concentrations at nerve endings. This reservoir effect typically extends the numbing duration by 1-2 hours beyond removal time. Additionally, the drugs bind to local tissues and nerve membranes, providing sustained effects even as plasma levels decline. The combination of stratum corneum reservoir and tissue binding creates the extended therapeutic window that makes Emla particularly useful for medical procedures that may take some time to complete.

Question 3

If Emla Cream enters the bloodstream, how long until it's completely out of my system?

Accepted Answer

When Emla Cream is properly used on intact skin, the small amount that enters the bloodstream (3-5% of applied dose) is completely eliminated within 4-6 hours after cream removal. Lidocaine has a half-life of 1.5-2 hours, meaning 50% is cleared every 1.5-2 hours, while prilocaine clears slightly faster with a 1-1.5 hour half-life. After 4-6 hours (approximately 3-4 half-lives), drug levels become undetectable in plasma. The metabolites continue to be excreted in urine for up to 24 hours, but these are inactive and pose no clinical concerns. Even with the maximum recommended application (60g on 600cm² for 5 hours), systemic levels remain well below toxic thresholds and complete elimination occurs within this timeframe in patients with normal liver and kidney function.

Question 4

Does Emla Cream work faster on children than adults?

Accepted Answer

Yes, Emla Cream typically works slightly faster in children due to anatomical and physiological differences. Children have thinner stratum corneum (approximately 30% thinner than adults), allowing faster drug penetration. Their skin is also more hydrated and has better blood perfusion, both enhancing absorption. However, the difference is modest - while adults need 60 minutes for optimal effect, children may achieve similar anaesthesia in 45-55 minutes. This is why paediatric guidelines still recommend 60 minutes application for procedures, ensuring adequate depth rather than minimal onset time. Importantly, infants under 3 months have different absorption characteristics and should never exceed 60 minutes application due to increased methaemoglobinemia risk. The slightly faster onset in children is a minor advantage offset by the need for careful dosing due to their smaller size and different metabolic capacity.