Hong Kong Med J 2020 Oct;26(5):464 | Epub 9 Oct 2020
Hong Kong Academy of Medicine. CC BY-NC-ND 4.0
LETTER TO THE EDITOR
Povidone-iodine and carrageenan are candidates
for SARS-CoV-2 infection control
KK Hui, BSc
Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong
Corresponding author: Mr KK Hui (kegankkhui@link.cuhk.edu.hk)
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To the Editor—Povidone-iodine, a candidate for
nasal spray and oral rinse, has displayed viricidal
effects on severe acute respiratory syndrome
coronavirus 2 (SARS-CoV-2) in vitro after 30 to 60 s
of exposure, even at concentrations as low as 0.45%.1
International dental and endodontics associations
have suggested povidone-iodine as a preprocedural
mouthrinse to limit the spread of SARS-CoV-2.2 In
a Letter to the Editor of Oral Oncology, Mady et al3
recommend nasal and oral povidone-iodine in head
and neck oncology patients and healthcare providers
every 2 to 3 hours, with a maximum of 4 times per
day to mitigate SARS-CoV-2 transmission. It is
noteworthy that hypo- and hyper-thyroidism are
possible adverse effects and contra-indications of
povidone-iodine use.4 Nevertheless, such adverse
effects are infrequent, and occur primarily after
long-term use (eg, >1 year).4 Povidone-iodine is also
contra-indicated with breastfeeding and pregnancy
due to the occurrence of neonatal hypothyroidism.5
After excluding contra-indications, povidone-iodine
mouthrinse or oral/nasal spray can reduce
SARS-CoV-2 viral load in the upper respiratory tract,
hampering transmission when used in conjunction
with existing infection control or public health
measures.
In addition to povidone-iodine, carrageenan in
over-the-counter lozenges or nasal spray may be an
appropriate candidate. As a sulphated polysaccharide
which cannot penetrate the mucosal membrane, it
acts through physically inhibiting viral attachment
and entry into host cells.6 7 Such non-specific
mechanism explains the broad viricidal activity
of nasal spray against enveloped (eg, influenza
and coronavirus) and non-enveloped viruses (eg,
rhinovirus) in vivo, with a greater reduction of disease duration and likelihood
of relapse among coronavirus patients.7 The latest
evidence further proves the tight binding of sulphated
polysaccharide to the spike protein of SARS-CoV-2.8
With low cytotoxicity and as a food additive classified
as “Generally Recognised as Safe”, carrageenan nasal
sprays demonstrate high tolerability.6 7 8
In conclusion, povidone-iodine and
carrageenan possess potential for use as
chemoprophylaxis or even in adjunct with the
current health behaviours (hand hygiene, face mask
use) and social distancing measures to synergistically suppress SARS-CoV-2 transmission.
Author contributions
The author drafted the letter. The author approved the final version for publication and takes responsibility for its accuracy and integrity.
Conflicts of interest
The author has disclosed no conflicts of interest.
Funding/support
This letter received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
References
1. Anderson DE, Sivalingam V, Kang AE, et al. Povidone-iodine
demonstrates rapid in-vitro virucidal activity
against SARS-CoV-2, the virus causing COVID-19 disease.
Infect Dis Ther 2020;9:669-75. Crossref
2. Jamal M, Shah M, Almarzooqi SH, et al. Overview
of transnational recommendations for COVID-19
transmission control in dental care settings. Oral Dis 2020
May 19. Epub ahead of print. Crossref
3. Mady LJ, Kubik MW, Baddour K, Snyderman CH, Rowan NR.
Consideration of povidone-iodine as a public health
intervention for COVID-19: Utilization as “Personal
Protective Equipment” for frontline providers exposed in
high-risk head and neck and skull base oncology care. Oral
Oncol 2020;105:104724. Crossref
4. Nobukuni K, Hayakawa N, Namba R, et al. The influence
of long-term treatment with povidone-iodine on thyroid
function. Dermatology 1997;195 Suppl 2:69-72. Crossref
5. Casteels K, Pünt S, Brämswig J. Transient neonatal
hypothyroidism during breastfeeding after postnatal
maternal topical iodine treatment. Eur J Pediatr
2000;159:716-7. Crossref
6. Eccles R, Winther B, Johnston SL, Robinson P, Trampisch M,
Koelsch S. Efficacy and safety of iota-carrageenan nasal
spray versus placebo in early treatment of the common
cold in adults: the ICICC trial. Respir Res 2015;16:121. Crossref
7. Koenighofer M, Lion T, Bodenteich A, et al. Carrageenan
nasal spray in virus confirmed common cold: individual
patient data analysis of two randomized controlled trials.
Multidiscip Respir Med 2014;9:57. Crossref
8. Kwon PS, Oh H, Kwon SJ, et al. Sulfated polysaccharides
effectively inhibit SARS-CoV-2 in vitro. Cell Discov
2020;6:50. Crossref