Embargoed until May 11, 2001
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Certain Nasal Saline Sprays Can Lead to the Destructionof Vital Cells that Fight Off SinusitisA preservative used to stop bacterial growth is toxic to the body's neutrophils
Palm Desert, CA -- Nasal saline spray (NSS) is available without a prescription and is frequently used in the treatment of sinonasal disease, as well as following sinus or nasal surgery. Potential benefits of NSS include moistening of dry nasal mucosa, clearance of debris from the nasal passageways, and improved mucous membrane function. NSS is conveniently packaged in multi-use bottles that make administration simple and relatively inexpensive.
However, multi-use containers are subject to bacterial growth over time unless antimicrobial preservatives are used in the solutions. The most frequently used preservative in NSS and other aqueous nasal sprays is benzalkonium chloride (BKC). This study suggests that NSS containing BKC, found in commercially available preparations, alters neutrophil morphology, decreases viability and increases neutrophil LDH activity in a concentration and time dependent manner. The research also finds that NSS is toxic to neutrophils in an in vivo model by exposure to oral mucosa. None of these effects were seen with phosphate buffered saline (PBS), which is similar in composition to NSS minus the preservative BKC.
Neutrophils are the primary cellular mediators of acute inflammation and are found abundantly on the mucosal surfaces of the nose and oral cavity. These cells provide a front line of defense against invading pathogens through their functions of phagocytosis (the process of ingestion and digestion by cells of solid substances) and degranulation (disappearance of cytoplasmic granules or lysosomes from a cell). Functional neutrophils must respond in adequate numbers if the body is to successfully combat infectious processes including sinusitis.
The authors of the paper, Effects of Nasal Saline Spray on Human Neutrophils, are Mark Boston, MD, Eric J. Dobratz, and David H. Darrow, MD, DDS, from the Department of Otolaryngology-Head and Neck Surgery and E. Stephen Buescher, MD, from the Center for Pediatric Research , at the Eastern Virginia Medical School and Childrenâs Hospital of the Kingâs Daughters, Norfolk, Virginia. The findings were presented May 15, 2001, at the 104th annual meeting of the Triological Society, held in Palm Desert, CA.
Methodology: Human neutrophils were exposed to nasal saline spray with the preservative benzalkonium chloride or phosphate buffered saline at varying times and concentrations. The cells were examined for morphological changes by light microscopy, and for viability as determined by trypan blue exclusion. Lactate dehydrogenase (LDH) levels were measured to quantify neutrophil cell destruction. In vivo morphologic changes were studied in neutrophils obtained from the oral mucosa in human volunteers who rinsed their mouths with either NSS or PBS.
Results: Neutrophils exposed to NSS concentrations as low as 15 percent showed near total cell destruction. Those exposed to 20 percent NSS demonstrated no cell viability by trypan blue staining. PBS-exposed cells were unaffected. Release of LDH from lysed neutrophils increased sharply at NSS concentrations >10 percent but remained stable in PBS-exposed cells. All neutrophils isolated from NSS oral rinses were lysed, while neutrophils from PBS rinses showed an average of 78 percent normal structure.
Conclusion: The study concludes that multi-use preparations of NSS are toxic to human neutrophils, and that substances used to preserve NSS, particularly BKC, are responsible for the toxicity. The destruction of neutrophils in the nasal mucosa may impair the cellular response to pathogenic organisms and lead to the release of inflammatory mediators, thus exacerbating the symptoms of rhinitis that NSS is intended to relieve.
The widespread use of NSS and common assumption that NSS is harmless necessitates a closer evaluation of its use and potential side effects. While there are few preservative-free steroid or topical decongestant preparations available, saline for nasal irrigation can easily be made at home without potentially harmful additives. Alternative preservatives and novel methods of preservative-free packaging of aqueous nasal sprays should be sought.
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