Tuesday, 1 November 2011

Oh my cold!

I’ve had a cold for several days and I hate it. What I hate the most is the running and stuffy nose. But the problem with cold is that you cannot cure it. The only thing you can do is to pass it and treat the symptoms. Many people think that you get stuffy nose because your nose gets filled up with mucus but the reality is a bit different. The main cause of the stuffy nose is the inflammation of the blood vessels in the nose. This makes the tissue in the nose to swell and get closer blocking the nose. We can find this type of inflammation in colds caused by viral infections and in allergic processes as well. Actually the production of mucus is a defensive mechanism that cells use to get rid out of the foreign agent (virus or particle that is producing the allergy).

As a pharmacist I can tell you that there are different anticatarrhal drugs and descongestant nasal sprays that you can use for these symptoms. These drugs help to get through the cold but you have to be quite careful with them. The anticatarrhal drugs usually have a combination of different drugs to treat different symptoms. They often have a pain killer and antipyretic drug like ibuprofen, paracetamol or salicylic acid, and one or two more drugs for the mucus, sneezes and stuffy nose. The most common combinations of these are salts of chlorphenamine and phenylephrine.

Phenylephrine is a derivative of ephedrine and it has been used in substitution of pseudoephedrine. The chemical difference between these molecules is not very big. Actually ephedrine and pseudoephedrine have the same chemical groups in their molecule but organised (orientated) in different ways. They are diastereomers..

Ephedrine and Pseudoephedrine are obtained from plants of the genus Ephedra and they act as alpha1 adrenergic agonist drugs (they bind to the receptors alpha1 of the nervous system). What they mainly do is to promote the contraction of the nose blood vessels to reduce the inflammation, reducing the stuffy nose at the same time. But these drugs have a big problem. Their chemical structure looks like the amphetamine and methamphetamine a lot.

These drugs are psycostimulants, produce euphoria and create addiction. As you can imagine that’s not really the effect a decongestant wants to produce and because of that the derivative used nowadays to treat the stuffy nose is phenylephrine. This has an extra hydroxyl group that makes this drug less similar to amphetamines.  Phenylephrine is used mainly in oral preparations but several studies carried out in 2006, 2007 and 2009 (two studies) have doubted its effectiveness, saying that its effect is not better than the placebo one. Interestingly, another study carried out by GlaxoSmithKline in 2007 showed that it does have effectiveness. The controversy is still out there but the Food and Drug Administration has stood by its 1976 approval of phenylephrine for nasal congestion as the debate continues.

But there are also topical preparations, like nasal sprays, that act specifically in the nose because it’s where the drug is delivered. In this case the drug used is called oxymetazoline. This drug is an alpha1 and partial alpha2 adrenergic agonist, and due to this effect in the alpha2 receptors its effects last for longer but are slower than the phenylephrine ones.

However topical decongestants as oxymetazoline can cause rebound congestion when the effects of the drug fade off. This will cause the use of the decongestant again in a vicious circle of persistent and worsening congestion, creating a kind of addiction to the decongestant.

As you can see there is no magic drug to get rid out of the stuffy nose and that’s quite annoying but I can tell you that if I have a cold I would never get on a plane without a decongestant spray.  If you don’t use this drug on time the pain can be really horrible. And that’s the least you want for starting your trip.

This post takes part of the VIII edition of the Carnival of Chemistry hosted in the blog Science Box.


Hendeles, L., & Hatton, R. (2006). Oral phenylephrine: An ineffective replacement for pseudoephedrine? Journal of Allergy and Clinical Immunology, 118 (1), 279-280 DOI: 10.1016/j.jaci.2006.03.002

Hatton RC, Winterstein AG, McKelvey RP, Shuster J, & Hendeles L (2007). Efficacy and safety of oral phenylephrine: systematic review and meta-analysis. The Annals of pharmacotherapy, 41 (3), 381-90 PMID: 17264159

Horak F, Zieglmayer P, Zieglmayer R, Lemell P, Yao R, Staudinger H, & Danzig M (2009). A placebo-controlled study of the nasal decongestant effect of phenylephrine and pseudoephedrine in the Vienna Challenge Chamber. Annals of allergy, asthma & immunology : official publication of the American College of Allergy, Asthma, & Immunology, 102 (2), 116-20 PMID: 19230461

Day JH, Briscoe MP, Ratz JD, Danzig M, & Yao R (2009). Efficacy of loratadine-montelukast on nasal congestion in patients with seasonal allergic rhinitis in an environmental exposure unit. Annals of allergy, asthma & immunology : official publication of the American College of Allergy, Asthma, & Immunology, 102 (4), 328-38 PMID: 19441605

Kollar C, Schneider H, Waksman J, & Krusinska E (2007). Meta-analysis of the efficacy of a single dose of phenylephrine 10 mg compared with placebo in adults with acute nasal congestion due to the common cold. Clinical therapeutics, 29 (6), 1057-70 PMID: 17692721

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