New aspects of the Slug Mucosal Irritation assay: predicting nasal stinging, itching and burning sensations

Stinging, itching and/or burning (SIB) sensations cannot be detected by animal tests or in vitro models. In the past, the Slug Mucosal Irritation (SMI) assay demonstrated a relation between an increased mucus production in slugs and an elevated incidence of SIB sensations in humans. A new 1-day SMI test procedure was developed focusing on the prediction of these short-term sensations. The objective of this study was to verify whether this new procedure is capable predicting mucosal tolerance of several marketed nasal formulations using the slug Arion lusitanicus. Irritation and tissue damage were quantified with a 5-day repeated exposure study by means of the mucus produced and proteins and enzymes released. The new protocol predicted SIB sensations by means of mucus production. The effects of six liquid nasal formulations were tested with both protocols, while five physiologic saline solutions were only tested with the new protocol to optimize it. None of the tested liquid nasal formulations resulted in tissue damage; however, exposure to the different formulations had a clear effect on the mucus production of the slugs and moderate discomfort was observed in some cases. These effects were due to the active ingredient, the presence of benzalkonium chloride as a preservative or the hyperosmolality of the formulation. For the most part results agreed with clinical data found in literature. It was concluded that the SMI assay, and the new 1-day protocol in particular, is a good tool to predict nasal clinical discomfort.