24 Use of Amethocaine Gel for Reducing MMR Vaccination Pain

Routine vaccination is the most common source of iatrogenic pain in healthy infants; the pain from this procedure has been shown to be ameliorated by the use of topical anaesthesia prior to vaccination. A novel, rapidly acting, local anaesthetic gel, Ametop™, which contains 4% amethocaine, has recently become available for clinical use. A double-blind, randomized placebo-controlled study was conducted to determine whether the use of Ametop™, decreases the pain associated with subcutaneous measles-mumps-rubella (MMR) vaccination in infants. Healthy infants receiving their routine 12-month MMR vaccination were randomized to receive 1 g of 4% amethocaine or a visually identical placebo on their deltoid muscle 30 minutes prior to vaccination. The vaccination procedure was videotaped and the Modified Behavioral Pain Scale (MBPS) was used to assess baseline and post vaccination pain scores; scores ranged from 0 (no pain) to 10 (worst possible pain) and the difference between pre and post vaccination pain scores was used as the net change in pain. One month post-vaccination antibody titers were measured to ensure that amethocaine did not interfere with the immunogenicity of the vaccine. Local skin reactions were also assessed. One hundred and twenty infants participated in the study; 60 were followed-up for assessment of antibody titers. There were no significant differences in infant demographic characteristics. The Ametop™ group (n=61) had significantly lower mean MBPS scores, than the placebo group (n=59); the net change in vaccination pain scores was 1.51 vs. 2.29 for the amethocaine and placebo groups respectively (p=0.029). The rate of vaccination success (antibody titers positive for measles, mumps and rubella) was not different between the amethocaine and placebo groups; 87% and 88% respectively (p=0.823). Overall, the amethocaine group developed significantly more local skin reactions than the placebo group, including erythema (p<0.001), pallor (p=0.014) and edema (p<0.001). All skin reactions were transient and self-limiting. Pretreatment with Ametop™ gel has been shown to significantly reduce the pain associated with subcutaneous MMR vaccination in one year old infants when compared to placebo and did not interfere with subsequent development of protective antibody levels. Further investigation of its safety during vaccination is recommended before widespread clinical use.