Electron microscopic investigations of the nasal mucosa after short term application of naphazoline nitrate (Privin®) in rabbits.

Background: Vasoconstricting nasal drops are applied frequently. Especially early ultrastructural alterations of the vessels were not examined up to now in animal models. Our goal was the systematic investigation of the submucosal vessels and the epithelium after topic application of naphazoline nitrate (Privin((R))) in an animal model. Methods: Three times daily over 6 days 3 mi of 0.1 % naphazoline nitrate solution (Privin((R))) were instilled into the right nasal cavity of 5 rabbits. At the 7th and 14th day an incisional biopsy of the lower nasal turbinate was carried out in ketamine/rompun anesthesia. Results: In the naphazoline group the capillaries showed an edematous endothelium with narrowed lumina. Thrombosis of the arterioles were frequently observed. The more cubic epithelial cells had deciliated areas with microvilli. Venules, submucosal glands and the surrounding connective tissue was normally configurated. Analogous findings were also observed after 2 weeks. Conclusions: The disturbance of the microcirculation shows impressive endothelial alterations. These structural changes can result in nonreversible mucosal damages. A regeneration time of more than 1 week is assumable. Our results should be considered critically in order to prevent damages of the nasal mucosa.