How to understand cough medicines

The average person takes a lot of over-the-counter cough medicines in their lifetime for little to no benefit.

The common cold, living up to its name, affects the average adult multiple times per year. There is no medication that actually attacks the viruses that cause colds; instead, there are different medications to alleviate different symptoms you may experience. Many are confusingly marketed, most people have no idea which medication will work for which symptom, and most over-the-counter medications might not actually work very well at all.

This post will attempt to help the average person understand which medicines they might actually want to take, and which are expensive wastes of your time.

There are multiple distinct types of medicine used to treat coughs and colds:

  • Decongestants try to clear the airways inside your head. This helps if you have a blocked nose, a sinus headache, or your ears won’t pop.
  • Expectorants and mucokinetics help you cough up mucus. This helps if you feel like your lungs and throat are full of gunk and you’re trying to cough it up in order to get it out.
  • Antitussives try to suppress the cough reflex. This helps if you have an unproductive cough – ie you keep coughing and it hurts but you’re not actually coughing anything up.
  • Painkillers are useful if you’ve got a headache, sore throat, sore chest, or whatever other kind of pain. Some of them also help bring down fever or reduce swelling.
  • Antihistamines are used to suppress allergic reactions. Sometimes cough and cold symptoms sort of look like allergic reactions, so we use antihistamines to maybe suppress the symptoms.
  • Substances like honey and mint oil help soothe your throat.
  • Some vitamins are necessary for the functioning of your immune system, and supplementing may help – especially if you’re one of the many people suffering from mild vitamin deficiencies.

The average person doesn’t need to know that much about medicine; you go to the doctor if you’re sick and the doctor tells you which medication to take. However, your doctor often isn’t involved when you visit the pharmacy to buy an over-the-counter cough remedy, so the average person probably should know a little about these – especially when some remedies don’t work and some of them do.

Decongestants

You will commonly encounter cough and cold remedies containing phenylephrine, which is sold as a decongestant. Unfortunately, phenylephrine doesn’t actually work.

Pseudoephedrine works great. The issue is that pseudoephedrine could theoretically be used to make meth. The government really doesn’t want you to make meth. So pseudoephedrine was banned or restricted in many jurisdictions, and pharmacies started selling phenylephrine instead, despite the minor inconvenience about phenylephrine not actually working. The average person doesn’t know that phenylephrine doesn’t work (though most oppose restricting pseudoephedrine if you ask them), so pharma companies continue making billions off it.

In some countries, you will be able to get pseudoephedrine by asking the pharmacist nicely; it won’t be available on the shelves but is available behind the counter. In the UK you can find it sold as ‘Day Nurse’. Frequently it will be mixed with high doses of paracetamol; this is partly because paracetamol is genuinely helpful in reducing pain and fever, and partly to ensure that you die of a paracetamol overdose if you try to take enough to get high off the pseudoephedrine. (Yes, the war on drugs is that counterproductive.)

In other countries, you can’t get pseudoephedrine at all, and you will just have to try regularly blowing your nose and staying hydrated.

The other common decongestant you will encounter is oxymetazoline or xylometazoline, which you’ll find under brand names like Otrivine. This should ideally be sprayed up the nose. These work within minutes to help clear your airways, because they’re “sympathomimetic” or “adrenergic” – that’s a fancy way of saying that they mimic hormones like adrenaline. Your body responds by constricting veins in your nose, which reduces swelling and opens up airways. Unfortunately, they can cause “rebound congestion” – after they wear off, the congestion can come back and sometimes it’s even worse than before (though evidence is mixed about whether the meds are at fault). The leaflets will warn you strictly not to take these for more than a few days. This is because they don’t want a situation where you take the medicine, then get rebound congestion, which makes you take more medicine, which makes you get more rebound congestion, and eventually you end up in the doctor’s office being told that your awful symptoms will go away if you stop constantly spraying adrenaline up your nose.

Follow all the instructions on the leaflets and labels and listen to whatever your pharmacist tells you. I’m not a doctor, so you should listen to doctors about whether these medicines are safe for you. Some medicines really shouldn’t be taken with MAOIs, or if you have high blood pressure or heart problems, or for whatever reason some of them are bad for you if you’ve got an enlarged prostate – don’t ask me, biology is bullshit.

Expectorants vs antitussives

You don’t take expectorants because you want to stop coughing. You take them because there’s thick sticky mucus in your lungs and throat, and it’s really uncomfortable and you’re trying to cough it up, but you just can’t seem to shake it loose. In other words, you want a ‘productive’ cough – a cough that actually gets the icky stuff out of your system. Once the mucus is out, you’ll stop needing to cough, so you’ll stop coughing so much.

That’s almost the opposite of what an antitussive does. An antitussive suppresses the urge to cough. It’s useful if there’s not really any mucus blocking anything, and you’re having an ‘unproductive’ cough – you’re not actually coughing anything up. Your cough reflex is just repeatedly being triggered by irritation at the back of the throat. If you keep coughing and coughing when you don’t need to, you’ll damage your throat – so you want to tell your body to please for the love of god stop triggering that reflex that isn’t achieving anything.

It’s really useful to identify which kind of cough you have, and then take the relevant medicine to actually help with the symptoms you want help with. If you’ve got a dry tickly cough, an expectorant won’t help.

If you’re looking for an expectorant, look for anything with the active ingredient “guaifenesin”. You can use cheap generic versions; so long as they contain “guaifenesin” they’ll work just as well as the expensive brand-name stuff. Guaifenesin is kind of hard to study, because it’s hard to measure that sensation of “oh thank god the sticky stuff that wasn’t coming out is finally coming out”, but patients usually say they’re satisfied.

There’s other expectorants. Acetylcysteine, which is mainly used to treat paracetamol overdose, might also work as an expectorant. Mucokinetics like carbocisteine or bromhexine thin mucus and reduce its viscosity. Ambroxol works on the mucus membranes to try and restore the body’s natural mucus-clearing mechanisms, including making an ‘anti-glue’ chemical that helps mucus stop sticking to the bronchial wall and possibly helping cilia (tiny hairs) to push mucus out. However, I’ve never seen any of these three actually on shelves, so you should probably look for guaifenesin.

It’s important to note that expectorants try to thin mucus by adding more water to the mucus so it’s easier to cough it up and out. This means you need to be hydrated. In fact, your first line of defence is drinking lots and lots of fluids, and if that didn’t work you should try guaifenesin. If you don’t drink enough while you’re taking lots of guaifenesin, you might get a kidney stone or something.

If you’re looking for an antitussive, look for anything with the active ingredient “pholcodine” or “dextromethorphan”. Codeine used to be prescribed as an antitussive, but NICE says it isn’t better than placebo whereas dextromethorphan probably works (both NICE and the Cochraine Review say that the evidence is mixed). Pholcodine is probably a little better, but not by much, and you can’t get it everywhere because it’s technically an opioid.

Again, listen to your doctor or pharmacist about whether you should combine these medicines with your existing health conditions and/or other medications.

Antihistamines

Antihistamines are definitely good at what they do, which is suppress histamine. Histamine is a chemical that your immune system makes when it detects a threat; it makes your eyes water and your nose run, and it makes you sneeze. That’s your body’s attempt to flush the threat out of your system – wash it out of your eyes and blow it out of your nose.

Allergic reactions happen when your body panics about something which isn’t actually a threat – like pollen – and you get all those symptoms even though they aren’t helpful. Antihistamines are fantastic as a treatment for allergic reactions. They make your immune system calm down about not-actually-threatening substances like pollen, which causes hayfever. They’re also used to literally save lives when people have acute allergic reactions in hospitals. They work.

Sometimes, cough and cold symptoms look a lot like allergy symptoms – red eyes, running nose, sneezing – so it makes sense that people tried antihistamines. Unfortunately it turns out that your body freaking out about pollen is a different thing from your body fighting an actual infection, and the evidence is pretty mixed. NICE says antihistamines don’t work for coughs and colds. Some overviews agree they aren’t effective. The Cochrane Review says they have some limited effectiveness in the short term (one or two days of treatment). Most sources suggest that antihistamines aren’t worth it in children, given the side effects and the mixed/limited evidence of efficacy, but adults might as well give it a go if they aren’t bothered by the side effects.

If you want an antihistamine, you’re looking for active ingredients like diphenhydramine, loratadine, cetirizine or promethazine. Again, anything with those active ingredients will work, and brand-name medications aren’t better than cheap generic ones.

Honey and mint

For a long time, science was quite confused about cough syrups. We kept doing studies on the active ingredients, and we kept discovering they were barely (if any) better than placebo. But people kept taking cough syrups and reporting that they felt much better. And then we discovered that up to 85% of the benefit of cough syrup comes, not from the ‘active ingredients’, but from the goddamn syrup. And what we thought was a “placebo effect” was an actual significant effect of sweet-tasting syrups.

This makes sense, because honey and lemon has been a home remedy for the common cold approximately forever. And honey also works, and is safe and effective for kids.

You can now buy cough syrups where the “active ingredient” is listed on the bottle as “glycerol”, presumably because consumers would not buy cough syrup if they marketed it as “literally just syrup LMAO, it turns out that active ingredients are an expensive waste of time”. I think this is definitely on my list of top 10 funniest facts in medicine.

There’s several reasons this works. Firstly, glycerol is a humectant, which means it attracts and absorbs water. You can use it to lubricate things or make them softer. It’s basically like applying moisturiser to the inside of your throat.

Secondly, honey has antimicrobial and anti-inflammatory properties and is basically some kind of magic that I don’t understand.

Thirdly, sweet tastes by themselves may suppress coughs – and mint might do the same thing. This is the reason why menthol or levomenthol can work, too. (Menthol or levomenthol is just a fancy word for mint oil. It’s commonly the active ingredient in medicines that you rub on your chest so that you’ll inhale the vapours.)

It turns out that your body can only really process a certain number of sensations at a time in the throat. There are cells in your throat that sometimes detect “oh no, an irritant!” and send a message to your brain saying that you need to cough to get rid of the irritant. Those cells can’t send that message if they’re busy sending messages like “SUGAR SUGAR WE LOVE SUGAR” or “ALERT! THIS MINT FLAVOUR IS REALLY COLD!” – and so you can suppress the cough reflex by literally just washing your mouth with sugar. If you inhale capsaicin, that’s an irritant, so you’ll cough – but if you firstly inhale mint vapour, it takes a lot more capsaicin to make you cough.

Don’t give honey to infants under 12 months old, because they can get botulism. Everyone else should literally just drink honey-and-lemon or glycerol syrup; it’s cheaper than cough medicine and works better.

Day vs night medications

Some medicines are marketed with different versions for ‘day’ and ‘night’. For example, in the UK we have ‘Day Nurse’ and ‘Night Nurse’.

The primary reason for this is that antihistamines make you drowsy, while most decongestants are also stimulants. You therefore don’t want to take pseudoephedrine if you’re trying to sleep, and don’t want to take antihistamines if you’re trying to get work done.

Look at the active ingredients of the medicine and decide whether you want it. It may not be worthwhile to take antihistamines if they make you drowsy, given the limited evidence base for efficacy – but if you want some help to fall asleep and you know they make you sleepy, I guess you should go ahead, since all the good actually-designed-to-make-you-sleep medicines are generally prescription-only. Not all decongestants will actually say on the packaging that they’re stimulants, but they are, so be aware of that when you are making informed choices about whether to take them in the evening.

Vitamins

Something like 40% of Europeans are deficient in vitamin D, and your risk is higher if you’re a dark-skinned person living in a low-sunlight country. It’s hard to tell if vitamin D is helpful since we keep doing small studies on mostly-not-deficient populations, but taking vitamin D probably won’t hurt you, and vitamin D deficiency has lots of really bad effects. COVID might be worse for you if you have a vitamin D deficiency, and vitamin D supplementation may help prevent COVID.

Regular supplementation of vitamin C and D may help prevent the common cold and reduce the duration of symptoms, but the evidence is mixed and the effect might go away if you adjust for confounders. It’s probably because your immune system is weakened if you have a deficiency in vitamins C or D, and there probably isn’t much benefit if you aren’t deficient – though one study found a linear relationship between vitamin D levels and seasonal infections. Zinc, meanwhile, works to help reduce the duration of colds if you start taking it when your symptoms start, and high doses are better (though you should not shove it up your nose – this can damage your sense of smell).

Echinacea might also work as a preventative.

Medicines you just shouldn’t take

Do not take antibiotics for the common cold. You will be contributing to antibiotic resistance, which kills people, and you will not get any better. The common cold is usually caused by a virus, so antibiotics won’t do anything at all.

Most corticosteroids and bronchodilators aren’t useful for treating common colds in healthy people. NICE thinks they should only be used if you have an underlying condition like asthma.

Heroin was once marketed as a cough suppressant. It was supposed to be a safer alternative to all those terrible cough suppressants that have opiates or morphine in. It turns out that heroin is actually not a nice safe non-addictive alternative. Please do not treat your common cold with heroin.

Conclusion

If you go to the pharmacy to get a remedy for the common cold, and you grab a random medicine off the shelf, the likelihood is high that you will pick up a substance that has not been consistently shown to work better than placebo. It is very easy to waste your money on medicines which add fancy active ingredients to sugar syrups but which don’t actually work any better than just drinking the sugar syrup. And if you don’t know the difference between an expectorant and an antitussive, you might pick up a medicine which isn’t right for the kind of cough you have.

Supplementing vitamins C and D might help prevent the common cold, and taking zinc might help shorten its duration. Staying well-hydrated will help with your symptoms. Drinking honey-and-lemon or glycerol syrup will help. If honey and lemon proves insufficient, reach for pseudoephedrine if your nose is blocked or you have a sinus headache, paracetamol if you’re experiencing pain and fever, guaifenesin if you want to cough up more mucus, or pholcodine or dextromethorphan if you’d like to suppress a cough. Antihistamines may be worth a shot if you’re sneezing lots or have red runny eyes. If you want your nose to unblock right now and don’t mind the chance of a rebound later, use a nasal spray containing oxymetazoline or xylometazoline. I have listed the active ingredients here; anything containing those active ingredients will work, and generic medications will work just as well as brand-name products.

Do not, under any circumstances, take antibiotics and/or heroin for your common cold. I am not a doctor. Don’t take anything which your doctor or pharmacist tells you not to take. Strongly consider wearing a face mask when you are indoors with other people, especially in poorly ventilated areas.

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