Transtympanic versus intramuscular steroid administration in a histamine-induced inflammatory middle-ear model

Abstract

Assessment of the histopathologic effect of transtympanic and intramuscular administration of dexamethasone in an in vivo experimental animal model of middle-ear mucosal inflammation. Fifty healthy rabbits weighting 1500-1800 g were randomly divided in three groups. In 10 animals (control group), 0.5 ml of a 20 mg/ml histamine solution was injected transtympanically. In 20 rabbits (group A), histamine challenge followed a three day intramuscular pretreatment with dexamethasone at 1 mg/kg per day. In 20 rabbits (group B), histamine challenge followed pretreatment with dexamethasone via a transtympanic route (0.3 ml, 1.2 mg dexamethasone). Middle-ear mucosa was obtained for histopathology 30 minutes after histamine administration. The following parameters were assessed: inflammation, acute inflammatory component, presence of eosinophils, inflammatory activity and fibrosis. Oedema, vascular dilatation and congestion, inflammation, the presence of an acute (polymorphonuclear) inflammatory component, the presence of eosinophils, and inflammatory activity were found to be of a lesser grade in the mucosae of group B. All differences were found to be statistically highly significant (p<0.01) using the Mann-Whitney test. Our findings validate the transtympanic route of dexamethasone administration in counteracting histamine effects.