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Recently news have come up that betadine/povidone-iodine mouthwashes should be used for prevention of COVID-19.

Betadine is an antiseptic. We use it in our clinic to clean a wound or after minor surgeries eg. extraction.

So are betadine mouthwashes effective against COVID-19? If yes, then how?

Reference

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    Personally, I think it's nonsense, but how would we know? The only study on the question has only just been launched. – Carey Gregory Jun 11 '20 at 14:23
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    @Carey Yes I agree. However there have been lot of news, If you check on the net. It's a recent idea. That's why I wanted to know the scientific basis of proposing this as a mouthwash as a preventive aid against COVID-19. – Ojasvi Jun 11 '20 at 14:40
  • I don't think there is a scientific basis, but mainly I don't think the question can be answered at this time. – Carey Gregory Jun 11 '20 at 15:04
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    @Carey yes. However I have put this question, if anyone has some information may be in future then can put that here. – Ojasvi Jun 11 '20 at 15:41
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    @CareyGregory - You opine too freely, and often harshly. I assure you, there is more than one study on this subject. – anongoodnurse Jun 11 '20 at 18:35
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Are betadine mouthwashes really effective against COVID-19?

In vitro (test tubes/culture plates) studies do show that providone iodine does kill viruses similar to SARS-CoV-2 after sufficient exposure (just as bleach and ethyl/isopropyl alcohol do.)

The answer in vivo (in humans or animals) is unknown. (N.B.: That's, unknown, as in, you should probably wait for more studies before (potentially serioulsy) harming yourself. Remember bleach, ethyl alcohol at or above 70% -140 proof - and certain industrial disinfectants do the same, which does not mean they should be used on human tissue. Most available PVP-I solutions available are toxic, even if diluted.)

The first study listed found that in vitro,

PVP-I gargle/mouthwash diluted 1:30 (equivalent to a concentration of 0.23% PVP-I) showed effective bactericidal activity against Klebsiella pneumoniae and Streptococcus pneumoniae and rapidly inactivated SARS-CoV, MERS-CoV, influenza virus A (H1N1) and rotavirus after 15 s of exposure.

It is only assumed that because it is effective against SARS-CoV, it is also effective against SARS-CoV-2.

It should be noted that not all providone-iodine solutions are created equally; the gargle preparation used in Japan cannot be obtained in the US and many other parts of the world, and the solutions used in the US are toxic at the same concentrations.

The second paper listed also notes

The utility and excellent safety profile of both topical nasal and oral solutions of PVP-I has long been recognized, especially at dilute concentrations (e.g. 0.001%). A detailed review of its virucidal activity against a wide range of common viruses, including SARS-CoV and MERS-CoV coronaviruses, is beyond the scope of this article.

The next line is

As a word of caution, in vitro studies using 10% and 5% PVP-I have demonstrated cilotoxicity on human respiratory cells.

They go on to propose use of PVP-I on patients known to or suspected of having Covid-19 on whom high-risk procedures are being performed (head/neck surgery) and on healthcare providers pre- and post- exposure to these patients (Apply nasal and oral PVP-I prior to and after patient contact (with repeated contact, apply every 2–3 h, up to 4×/day) in healthcare providers that who lack adequate PPE (e.g. N95, PAPR).

They go on to conclude, in part,

It is important to acknowledge that there is a potential risk in that prophylactic treatment of healthcare providers could increase susceptibility to SARS-CoV-2 infection by affecting mucociliary function or local immunity.

One study seems stalled (cause unknown, recruitment issues?)

while another tested (in vitro) a very specific kind of PVP-I (gel-forming) in very limited circumstances.

The last paper is detailed and thorough (though please note the word potential in the title), and you can skip directly to the PVP-I section, where they state

[the Japanese] mouthwash is not available in the United Kingdom, although may still be purchased in Germany and other countries. As a 1% solution, PVP-I is available in Hong Kong, Korea, Singapore, Malaysia, Philippines, and Taiwan.

In Vitro Bactericidal and Virucidal Efficacy of Povidone-Iodine Gargle/Mouthwash Against Respiratory and Oral Tract Pathogens
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
COVID-19: Povidone-Iodine Intranasal Prophylaxis in Front-line Healthcare Personnel and Inpatients (PIIPPI)
In-Vivo Toxicity Studies and In-Vitro Inactivation of SARS-CoV-2 by Povidone-iodine In-situ Gel Forming Formulations
Potential Role of Oral Rinses Targeting the Viral Lipid Envelope in SARS-CoV-2 Infection

Edited to add: In case there is confusion, I stated that the answer is unknown, and that most PVP-I solutions available are toxic in most countries. I am not an advocate of its use any more than 70% ethyl alcohol or bleach!

I answered this question because it's important to engage with people reaching out for some answers in this pandemic, and because harmful advice is rife now (Even national leaders are making them, and they are surrounded by experts.) And to show that their concerns weren't unshared by some physicians. And that, like Barry Marshall's discovery, sometimes it's the most "ridiculous", "preposterous", and "idiotic" things that turn out to be true in medicine. But Barry Marshall paid a high price to prove his theory, both physically and emotionally, though winning the Nobel Prize was a very nice apology and recognition of the millions upon millions of people he saved from the barbaric approach to chronic ulcer treatment and stomach cancers before his discovery.

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    Seems biologically implausible a mouth wash is going to affect the nasopharynx, and also penetrate into salivary gland ducts. Also, when I apply povidine iodine to the skin I wait for it to dry before I consider the skin "clean". And if these respiratory viruses are in the mouth, they are almost certainly in the alveoli as well. – Graham Chiu Jun 11 '20 at 22:02
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    @GrahamChiu - Clearly you read none of the links; most use some form of nasal application as well. In Japan, I think it's only gargle, but I'm not sure. Also, please note I'm quoting papers, not forwarding my own opinion. So read the papers and argue with the authors. Closed minds are an impediment to science. Ask Nobel Prize (Medicine) winner Barry Marshall. Also, so you let PVP dry. I only kinda do that for spinal taps; I'm liberal with the wet stuff and when sufficient time has gone by, I wipe some of it off with sterile gauze. Finally, again, Read the links. – anongoodnurse Jun 12 '20 at 12:50
  • you quoted mostly in vitro studies, and their speculation about in Vivo use. If there were something truly relevant to the question you should have quoted it rather than ask us to read the papers. I'm just voicing a skeptical viewpoint. – Graham Chiu Jun 12 '20 at 23:39
  • @GrahamChiu - I answered the question. Speculation is all that's available, and if you even read the quotes, you'd have seen that nasal application was involved. Read the entire answer before speculating yourself. – anongoodnurse Jun 12 '20 at 23:44
  • The question links to an article about using PI gargles 4x a day to prevent COVID-19. I repeat that this is biologically implausible since it's a respiratory virus that attacks alveoli. – Graham Chiu Jun 12 '20 at 23:51

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