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.