Background: EMLA is a topical anesthetic used to decrease procedural pain. Research in neonates is limited due to concerns that it may cause methemoglobinemia in this age group. The objective was to assess the safety of single doses of EMLA in premature and full-term neonates.

Methods: Premature neonates aged 30 to 37 weeks gestation undergoing heel lancing were included in the first two phases of the study. In phase 1, 0.5 g was applied to the heel in a randomized, double-blind controlled manner and covered with an occlusive dressing for 0.5 hour. In phase 2, 0.5 g was applied to the heel for 1 hour in an open study design. Phase 3 included full-term neonates undergoing circumcision. Using a randomized, double-blind controlled design, 1 g of EMLA was applied to the penis for 1 hour. Methemoglobin (Met-Hb) levels, expressed as a percentage of hemoglobin, were measured 1 to 18 hours after drug exposure, according to randomization. Met-Hb levels were compared with baseline levels in the same subject (phase 2) or a control group (phases 1 and 3) matched for age. Neonates were also monitored for up to 24 hours for clinical signs of methemoglobinemia.

Results: Mean Met-Hb levels did not differ between EMLA-exposed neonates and controls (see table below). Clinical signs of methemoglobinemia were not observed in any of the subjects.

Table 1
Full size table

Conclusion: Administration of EMLA was not associated with significant increases in Met-Hb levels. This study suggests that the risk of methemoglobinemia from a single dose of EMLA is small. Future studies should establish the efficacy of EMLA in this age group before it is routinely utilized for the management of pain. (Supported in part by Astra Pharma Inc., Canada).