Introduction
Anosmia is the inability to smell which may be partial or total. Recently, anosmia considered a characteristic sign that helps in the diagnosis of COVID-19. The exact underlying pathogenesis is not well understood 1. Different studies investigated the relationship between olfactory dysfunction post COVID-19 and the recovery rate of loss of smell. In the first 2 months, it was reported that 79.5% of patients may expect a complete recovery of the olfactory function. Also 20.5% of patients could not achieve normal levels of olfactory function 2.
The nasal cavity is the first gateway for the initial infection as viral loads in the patient’s nasal cavity are higher than the viral loads in the pharynx. Also, the nasal cavity environment plays an important role in the process of olfaction transmission from the nasal cavity to the central processing system 3.
Calcium cation has been shown to play an essential role in the mechanism of smell transmission through inhibitory feedback inhibition approach. This inhibitory role is currently thought to occur through two distinct mechanisms 4. First, calcium calmodulin interacts directly with the cyclic nucleotide-gated channels, resulting in decreased sensitivity of the channel to cyclic nucleotides and thus decreased positive current influx. Second, calcium-dependent phosphorylation of adenylyl cyclase results in decreased production of intracellular cyclic adenosine monophosphate and thus decreased activation of cation channels controlled by cyclic nucleotides. Accordingly, it has been suggested that reducing intranasal free calcium may improve olfactory function in patients with anosmia related COVID-195.
Pentasodium diethylenetriamine pentaacetate (DTPA) is a potential chelating agent used for complexation and sequestration of metal ions. It has the ability to chelate divalent and trivalent metal ions. DTPA is used in a variety of cosmetic products to remove calcium and magnesium cations that interfere with foaming and cleansing performance and that can cause turbidity in clear liquids 6,7. DTPA has a high chelating capacity for calcium cations in an alkaline pH medium and forms a stable complex product, suggesting that reducing intranasal free calcium may improve anosmia in patients post COVID-19 infection.
The main objective of this work is to test the effect of topical DTPA on reducing the increase of calcium cations in the mucus of patients with anosmia related COVID-19. This is the first published clinical trial testing DTPA as a topical treatment to improve anosmia post COVID-19 infection.