UK trials have begun of a nasal spray that could prevent COVID-19 infections

A few weeks ago, it was announced that UK trials were beginning of a nasal spray proven to kill 99.9% of the coronavirus that causes COVID-19. The idea, broadly, is that you’d use the spray first thing in the morning, during the day after social interactions, and then again in the evening — and it would prevent the virus from taking hold and making you ill.

Awesome, right? Simple, cheap, portable. Sort of like cleaning your teeth regularly: prevention rather than cure. Combined with a vaccine, particularly for anyone at high risk such as those in healthcare settings, it could put a stop to the whole thing — and might also turn out to be effective on other, less deadly but still annoying, viruses.

But, I hear you ask, what is it? Because if I’m going to squirt something up my nose several times a day, I have questions…

Nitric oxide has the chemical formula NO

Fair enough. It’s actually, mostly, nitric oxide, which has the chemical formula NO.

Yes, there are plenty of wordplay options here. The researchers have already jammed the letters NO into their company name, and done the acronym thing, to get SaNOtize Nitric Oxide Nasal Spray (NONS). If the trials are successful, it’s probably only a matter of time before we get: “Say NO to coronavirus!” marketing. (Any ad agencies reading this, I’m claiming copyright.)

But that aside, unless you’re a chemist you might be thinking about some half-remembered chemical names and frowning at this point. Isn’t that… used in rocket fuel? Or… wait… isn’t that… the nasty smoggy stuff that causes lung problems?

Ah, well, there are several nitrogen oxides. Let me summarise:

• NO is nitrogen monoxide or nitric oxide — that’s what we’re talking about here.
• NO₂ is nitrogen dioxide — forms when combustion happens in air, and it’s the one that’s brown and smells horrible, and is probably most associated with photochemical smog (although atmospheric NO has a significant role there, too).
• N₂O is nitrous oxide, sometimes just “nitrous” — that’s the one that’s also called laughing gas and is used as an anaesthetic, and “recreationally,” as well as being used to increase the power output of engines.
• NO₃ is nitrogen trioxide — this is a radical, with an unpaired electron. It’s unstable, but it is important in ozone chemistry.
• N₂O₄ is nitrogen tetroxide or dinitrogen tetroxide — this is important because it forms an equilibrium with NO₂ so the two can be thought of an interconvertible, and also because it’s used as a rocket propellent.

Nitric oxides in the atmosphere cause photochemical smog.

There are other nitrogen oxides, not to mention ions — but let’s not spend all day on this. Nitrogen forms this confusing hodgepodge of oxides because it has five electrons in its outermost shell (it’s in group 15 of the periodic table) and because there’s not much difference in the electronegativities of oxygen and nitrogen. So essentially, it can share electrons with oxygen to form bonds in a number of different ways to obtain a stable, full outer shell.

For any students reading this, I’m sorry. You… pretty much just have to remember these. Yes, I know. That’s why experienced chemists so often use the shorthand NOx — we just can’t be bothered keeping all the names straight. (Okay, before someone shouts at me, actually NOx is handy because we’re often talking about more than one oxide at a time, and it allows us to easily express that.)

Back to NO. It’s a colourless gas, and it has an unpaired electron, which makes it a free radical. And… here we go again. Aren’t we supposed to eat lots of antioxidant-rich fruit and vegetables to mop up free radicals? They’re bad, aren’t they?

Viagra (Sildenafil) makes use of the nitric oxide pathway which causes blood vessels to dilate…

Yes and no. Free radicals are reactive species which damage cells and can cause illness and ageing. Too much exposure to free radicals causes something oxidative stress, which is definitely bad. But. It turns out that nitrogen oxide is an important signalling molecule, that is, a molecule which is the body uses to send chemical signals from one place to another. In particular, nitrogen oxide “tells” the smooth muscle around blood vessels to relax, causing those blood vessels to dilate, and increasing blood flow. Viagra (aka Sildenafil) uses the nitric oxide pathway, and I think we all know what that does, don’t we? Good.

Nitric oxide has also been shown to reduce blood pressure, which is generally considered a good thing — up to a point, obviously. This is why you can buy lots of so-called nitric oxide supplements, which, since nitrogen oxide is a gas at room temperature, don’t actually contain nitric oxide on its own. Rather, they’re a mixture of amino acids and other things that supposedly help the body to make NO. But it might be cheaper, and healthier, to eat plenty of beetroot or drink beetroot juice, since there’s evidence that does the same sort of thing.

As always, the dose makes the poison. Too much nitric oxide is definitely problematic, but administered in the right way and in appropriate doses, it’s extremely safe.

It’s suggested that the nitric oxide in the SaNOtize nasal spray destroys the virus and also helps to stop viral replication within cells. Plus, it blocks the receptors that the virus uses to enter cells in the first place. Essentially, it locks the doors and rains down fire on the potential intruders — nice work.

You only need to use the spray occasionally, because developing a COVID-19 infection isn’t instant. First the virus gets into your nose, then it attaches to cells, then it replicates, and then it sheds into your lungs. There are timescales involved here — so long as the spray is used every so often it should do the trick.

Another advantage is that this should, theoretically, work on other strains — where the current vaccines may not. So it could provide a very important stopgap when vaccination isn’t immediately available.

This is only in the early stages of clinical trials so, for now, wear your mask.

All sounds fabulous, doesn’t it? It might be, but, we’re in the early stages with this. Clinical trials have now started in the UK, are already in Phase II in Canada and have been approved to start in the USA. Researchers are hopeful, but we need to wait for the evidence.

So in the meantime, wear a mask, wash your hands, and take a vaccine if you’re offered one. Stay safe out there!

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