The effect of topical doxycycline in the prevention of experimental tympanosclerosis.

Objective: The aim of this study is to determine the effectiveness of topical doxycycline used in the process of experimental myringosclerosis and tympanosclerosis.

Methods: A prospective experimental animal study. Methods: Experimental tympanosclerosis was accomplished in 25 healthy adult guinea pigs by inoculation with 2.5 x 10(7) colony-forming units of type-3 Streptococcus pneumoniae microorganisms followed by bilateral myringotomy. While the animals' right ears received a topical doxycycline treatment daily, their left ears were left untreated and used as controls. Otomicroscopic examination was carried out weekly and healing tympanic membranes were remyringotomized. After a 6-week follow-up, the temporal bones of 24 of 25 animals were removed and light-microscopy examination was done regarding tympanic membrane myringosclerosis and middle ear mucosal sclerosis.

Results: Myringosclerosis was noticed to a lesser extent in the doxycycline-treated group when compared to the untreated control group. Light microscopy evaluation revealed a difference in the area and thickness of the sclerotic plaques of myringosclerosis of the tympanic membranes in the doxycycline-treated group and the control group, being significantly smaller and thinner in the treated group (P < .001, P < .04, respectively). Similarly, the area and thickness of the sclerotic plaques in the middle ear mucosa were significantly smaller and thinner in the doxycycline treated group (P < .001, P < .03).

Conclusions: This study demonstrated that the potent matrix metallo-proteinase inhibitor doxycycline plays a preventive role in the development of experimentally induced tympanosclerosis.