Effects of EMLA Cream on the Structure of the Rat Tympanic Membrane

Goh, Eui Kyong; Chon, Kyong Myong; Moon, Young Il; Lee, Ji Won; Cho, Jae Min; Lee, Jae Woo

Abstract

BACKGROUND: EMLA cream is a eutectic mixture of lidocaine and prilocaine and has excellent anesthetic effect on tympanic membrane but histologic influence on tympanic membrane is uncertain.
OBJECTIVE
To investigate its histologic effects on tympanic membrane.
MATERIALS AND METHODS
18 Sprague-Dawly rats were divided into 6 groups. Each group was treated with application of EMLA cream into external ear canal and then were sacrificed at 4 hours, 24 hours, 3 days, 7 days, and 14 days after application of the agents.
RESULTS
1) Transmission electron microscopy revealed partial loss of epithelial cell at 4 hours after application of the agents. 2) The specimen showed damaged cells in the epidermal layer and partial loss of basement membrane at 24 hours after application of the agents. 3) At 1 week after application of the agents epidermal layer and inner epithelium with connective tissue predominated. Thus the fibrous layer represent only 1/3 of total drum thickness. In the basal layers widened intercellular spaces were noted. 4) At 2 weeks after application of the agents newly formed connective tissue was found at fibrous layer and numerous fibroblasts were noted at inner epithelial layer. but overall histologic changes of the drum were not significant and healing processes was noted.
CONCLUSION
EMLA cream has less histopathologic effects on tympanic membrane, and early recovery process occurred.