The effects of almond oil on rhinitis medicamentosa induced by long-term topical oxymetazoline use in rats

ABSTRACT Objective: The aim of this experimental animal study was to determine the histopathological changes that occur in the nasal mucosa in rhinitis medicamentosa and to introduce a novel potential treatment option that could serve as an alternative to topically applied steroids currently used based on clinical experience yet lacking proven efficacy. Methods: Forty male rats were included in this study. In 32 rats, drug-induced rhinitis was established by intranasal administration of oxymetazoline three times per day for 60 days. Eight rats that received only physiological saline served as the control group. At the end of 60 days, eight rats from both the saline-control group and the oxymetazoline group underwent preliminary evaluation, confirming the development of drug-induced rhinitis in the oxymetazoline group. The remaining 32 rats with confirmed drug-induced rhinitis were divided into three subgroups (n=8 each): (1) a treatment control group receiving intranasal physiological saline for 15 days, (2) a group receiving intranasal mometasone furoate, and (3) a group receiving intranasal almond oil. The rats were then sacrificed, and histopathological changes in the nasal mucosa were quantitatively scored and statistically compared among the three groups. Results: Preliminary analysis showed significantly higher median subepithelial edema, inflammation, congestion, submucosal gland degeneration, and total median scores in the oxymetazoline-induced rhinitis group compared with the control group (p<0.001, p=0.001, and p=0.002, respectively). In comparing the treatment groups, median subepithelial edema and congestion scores were significantly lower in the almond oil group than in the mometasone furoate group (p=0.017 and p=0.015, respectively). Additionally, the median inflammation and submucosal gland degeneration scores were significantly lower in the almond oil group than in the treatment control group (p=0.025 and p=0.02, respectively). Notably, when all histopathological parameters were assessed collectively, the almond oil group had a significantly lower total median score compared with both the treatment control and mometasone furoate groups (p=0.007 and p=0.001, respectively). Conclusions: Intranasal administration of almond oil was found to be more effective in treating drug-induced (medicamentosa) rhinitis in rats than intranasal steroids, suggesting that it may serve as a promising alternative therapy. Keywords: Drug-induced rhinitis, almond oil, nasal steroid, nasal mucosa, nasal decongestan