The efficacy of betahistine as treatment for eustachian tube dysfunction in an allergic rat model
Wilson, James David
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Otitis media is a quite common disease, especially in children due largely to their underdeveloped Eustachian tubes. One potential factor, thought to be a large contributor to the disease, is an allergic reaction causing congestion and blockage of the Eustachian tube, leaving the middle ear prone to bacterial infection and effusions. The H3 receptor has recently been discovered in the nasal mucosa of humans and rodents and is linked to the immune response. Excess histamine released in an allergic response causes nasal vascular constriction and congestion. By blocking the H3 receptor, the local vasculature may be allowed to dilate, resulting in decongestion. This could play a large role in the treatment of otitis media with effusion. The effectiveness of betahistine dihydrochloride, an H3 receptor blocker, in providing possible relief from middle ear congestion was tested using a rat model. An allergic response was induced in rats followed by one of two betahistine dihydrochloride treatment regimens: drug delivery via transtympanic or intranasal route. Changes in Eustachian tube function were monitored during this process. Four measurements were used to measure the function of the Eustachian tube: passive opening pressure, passive closing pressure, active clearance of negative pressure, and Mucociliary transit time. Lower opening pressure and closing pressure, higher clearance of negative pressure, and shorter Mucociliary transit time were indications of better Eustachian tube function. Regardless of delivery method, no significant results were found among the experimental groups to suggest improved Eustachian tube function after drug treatment. Although the middle dose of betahistine dihydrochloride (50 mg/mL) delivered transtympanically followed the expected response outcome, the trend did not achieve statistical significance. Overall, the results of this study are inconclusive for measuring the beneficial effects of betahistine dihydrochloride on Eustachian tube function. Further investigations are being conducted to measure the magnitude and duration of the effects of allergic responses on Eustachian tube anatomy and physiology.