ABSTRACT
BACKGROUND: Olfactory dysfunction is recognized as a symptom of COVID-19. Reports revealed the nasal calcium increase has adverse effects on olfactory function. Tetra sodium pyrophosphate, a chelating agent, can bind calcium and help improve olfaction. METHODS: Sixty-four patients with olfactory dysfunction persisting for more than 90 days after COVID-19 were recruited. Participants were divided into 2 groups that received either 0.9% sodium chloride or 1% tetra sodium pyrophosphate for topical application. Olfactory function was tested with the Sniffin' Sticks test before treatment and 1 month later. In addition, nasal calcium was determined with an ion-selective electrode. RESULTS: After topical application of tetra sodium pyrophosphate compared to sodium chloride, improvement from anosmia to hyposmia with decrease in calcium level was demonstrated. As for the results of tetra-sodium pyrophosphate, 81% showed improved olfactory function and 19% did not exhibit olfaction improvement. CONCLUSIONS: Intranasal application of tetra sodium pyrophosphate may be associated with improvement in olfactory function after COVID -19 infection. Trial registration Ethical Committee of Damietta Faculty of Medicine approved this study on January 2021 (approval number, IRB 00012367-21-03-010).