07-06-09 EMLA Revisited

EMLA revisited

A couple of questions arose after last weeks Question of the Week on EMLA.

Is EMLA safe to use in neonates e.g. <28 days of life?

The package insert specifically advises against use in children less than 3 months of age due to the risk of methemoglobinemia. There have been numerous studies in the pediatric literature regarding use of EMLA for neonatal circumcisms, lumbar punctures, suprapubic taps, venipuncture, heel sticks, etc without the incidence of clinical methemoglobinemia. The concern in infants is that they may have 1) increased percutaneous absorption due to the characteristics of their stratum corneum 2) increased risk of methemoglobinemia due to the presence of fetal hemoglobin and 3) reduced capacity for reduction of the methemoglobinemia due to decreased methemoglobin reductase function. Neonates who are sick or who may be on other oxidizing medications may be at higher risk.

Risk is relative, so awareness of the possible complication of the use of EMLA in this population is probably the most important take home message.

What about the use of EMLA cream in the setting of venipuncture for hemodialysis through a patient's hemodialysis fistula?

For patients with intact skin, EMLA may be very useful to reduce the pain of venipuncture; however, in settings of repetitive use, local skin irritation and allergic contact dermatitis may occur. For patients with end stage renal disease, use of EMLA is rarely associated with systemic toxicity or methemoglobinemia if used correctly. There have been case reports of dermatitis occurring in ESRD patients who have confirmed positive patch testing. For those patients, cessation of use usually resolves the problem.

Question prepared by: Saralyn Williams, M.D. Medical Toxicologist

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