Effects of topical anesthetics on tympanic membrane structure.
Topical application of a local anesthetic agent can induce adequate insensibility to pain, and therefore can avoid the use of general anesthesia or invasive infiltration techniques for myringotomy or the insertion of a tympanostomy tube. A comparative study was conducted on a guinea pig animal model to determine the effects of three agents on the structure of the tympanic membrane: 5% tetracaine base dissolved in dimethylsulfoxide (DMSO), pure DMSO, and Bonain's solution. Survival times ranged from 1 day to 3 months. Following removal from the animals, membranes were embedded in Spurr and cut in semithin sections. Signs of mild or severe external otitis were frequent; to avoid non-specific results, infected specimens were not evaluated. Bonain's solution caused loss of the epidermis and mucosal epithelium within 1 day of treatment. The connective tissue layers of the drum were severely hyperplastic after a survival time of 1 month. Tetracaine base in DMSO caused a loss of epithelium and mucosal cells in 3 days. Regeneration started within 7 days and a restitution to integrity was seen after 3 months in drums treated with tetracaine base or DMSO alone.
Strutz
J
J
Department of Oto-Rhino-Laryngology, University of Freiburg, Federal Republic of Germany.
Blessing
R
R
Zöllner
C
C
D000287:Administration, Topical; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D003042:Cocaine / Q000008:administration & dosage / Q000494:pharmacology; D004121:Dimethyl Sulfoxide / Q000008:administration & dosage / Q000494:pharmacology; D004338:Drug Combinations; D006168:Guinea Pigs; D008610:Menthol / Q000008:administration & dosage / Q000494:pharmacology; D019800:Phenol; D010636:Phenols / Q000008:administration & dosage / Q000494:pharmacology; D012996:Solutions; D013748:Tetracaine / Q000008:administration & dosage / Q000494:pharmacology; D014432:Tympanic Membrane / Q000187:drug effects*
D000779:Anesthetics, Local; D004338:Drug Combinations; D010636:Phenols; D012996:Solutions; D013748:Tetracaine; D008610:Menthol; D019800:Phenol; D003042:Cocaine; D004121:Dimethyl Sulfoxide