Doxycycline Improves Quality of Life and Anosmia in Chronic Rhinosinusitis With Nasal Polyposis: A Randomized Controlled Trial

Background Chronic rhinosinusitis with nasal polyps (CRSwNP) is a complex disorder and effective treatment remains a major challenge. Some antibiotics with anti-inflammatory properties are reported to have potential to be used as an adjunct therapy in the management of chronic airway inflammation. Objective The aim of this study was to evaluate the efficacy of doxycycline in CRSwNP. Methods In this randomized, double-blind, placebo-control study, we assessed the efficacy of doxycycline in patients with moderate to severe CRSwNP. A total of 100 patients were randomly assigned to receive either doxycycline (200 mg on the first day followed by 100 mg daily) or placebo for 6 weeks. All patients received baseline therapy with fluticasone, montelukast, and nasal irrigation during the study. The primary outcome was quality of life based on the sino-nasal outcome test (SNOT-22) questionnaire. We measured peak nasal inspiratory flow (PNIF) and severity of symptoms by visual analogue scale (VAS). Baseline blood eosinophil count, serum IgE level, eosinophil in nasal secretions, and Lund-Mackay score based on low dose paranasal CT scan were also recorded. Results Treatment with doxycycline significantly improved SNOT-22 ( P = .037) and sense of smell ( P = .048). The baseline SNOT-22 score had no effect on outcomes. The effect of doxycycline on quality of life in patients with or without nasal eosinophilia was not significantly different. Change in SNOT-22 score was also not correlated with serum IgE ( P = .220, r = −0.186) and the eosinophil count ( P = .190, r = −0.198). Conclusion Doxycycline improves the quality of life in patients with CRSwNP. It also has temporarily beneficial effects in improving the sense of smell. The levels of eosinophil in the blood and nasal secretions do not affect the response to treatment. Hence, doxycycline can be used in both eosinophilic and non-eosinophilic nasal polyps. This study was registered at Iranian Registry of Clinical Trials. https://www.irct.ir/ IRCTID: IRCT20210403050817N1.