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.
References:
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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