Topical amethocaine gel 4% for intramuscular injection in term neonates: a double-blind, placebo-controlled, randomized trial.

BACKGROUND: Topical local anesthetic agents such as amethocaine penetrate intact skin and block pain signals originating from the dermis during medical procedures. They have been found to attenuate pain from various procedures, including intramuscular (i.m.) injection of vaccines. Published data on their effectiveness for i.m. injection of vitamin K in neonates were not identified.

OBJECTIVES: The primary objective of this study was to evaluate the analgesic effectiveness and tolerability of topical amethocaine gel 4% in neonates undergoing i.m. injection of vitamin K. The secondary objective was nurses' response to the use of the intervention and possible barriers associated with its incorporation into clinical practice.

METHODS: In a double-blind, placebo-controlled, randomized trial, full-term neonates in the Labor and Delivery Unit of Mount Sinai Hospital, Toronto, Ontario, Canada, received 1 g of amethocaine gel 4% or placebo 30 minutes prior to i.m. injection of 0.5 mL of vitamin K. Pain responses were assessed using percent facial grimacing score, percent cry duration, and latency to cry from video recordings. Parents and nurses assessed infants' pain response using a visual analog scale (VAS). Local adverse events (ie, erythema, blanching) at the application site were recorded. Nurses were asked to provide written responses regarding their willingness to incorporate local anesthetics in clinical practice and barriers to their use.

RESULTS: From July 2003 to December 2004, 175 families were approached for participation in the study; 52 declined consent and 13 were not randomized. One hundred ten neonates were enrolled and evenly randomized to each group. Baseline characteristics were similar in both groups. During i.m. injection, the mean (SD) percent facial grimacing score was 70% (30%) for the amethocaine group compared with 75% (34%) for the placebo group (P = 0.41). The mean (SD) for percent cry duration was 55% (34%) compared with 62% (38%), respectively (P = 0.34). The mean (SD) latency to cry was significantly longer in the amethocaine group compared with the placebo group (4.7 [4.5] vs 2.7 [2.3] seconds; P = 0.01). Parents' and nurses' VAS ratings for infant pain did not differ between groups. The incidence of adverse events did not differ between groups. Ninety-seven percent of nurses (89/92) said they would use the intervention. Fifty-seven percent of nurses (52/92) identified barriers to incorporation with the primary reason being time constraint (67% [35/52]).

CONCLUSIONS: Topical amethocaine gel 4% was ineffective in reducing pain on i.m. injection of vitamin K in these full-term neonates. Treatment was generally well tolerated and nurses concluded that, given the choice, they would use a topical anesthetic.