Complex choices in tackling common cold
An intriguing discussion by Victoria Ashton in the November 2003 issue of Chemistry in Britain reveals some of the complexity involved in the choice of a remedy for treating the common cold. So prevalent is this winter complaint that we have all developed our own strategies for dealing with it. Some put their faith in the sophisticated mixture
of antitussives, analgesics and syrupy components purchased over the
pharmacy counter. Others, possibly influenced by the wisdom of a grandmother,
will resort to honey and lemon, perhaps with a dash of spirit, or a
tisane made with chosen herbs. There is no agreement regarding the
efficacy of a particular preparation. And over the whole problem is
the difficulty of how powerful is the placebo effect.
Unfortunately, the common cold has many symptoms, each of which may present
a different priority in different individuals. Headache, sore throat,
congested nasal passages and fever affect people in different ways, and
no universal panacea exists to suppress or relieve all symptoms in turn.
It is estimated that sick leave attributable to colds costs United Kingdom
businesses some £1,300m annually, with symptoms lasting a few days
to several weeks. Over-the-counter cold remedies involve the expenditure
of about £100m every year.
Remedies are of many sorts, according to the salient symptoms being treated.
Cough demands a suppressant, which may be an opiate such as codeine,
pholcodine or dextromethorphan, formulated in a soothing syrup. However,
there is some evidence that cough medicines containing codeine or dextromethorphan
may be only 10–15 per cent better at suppressing cough than the
placebo effect of the syrupy vehicle alone. Indeed, the placebo effect
of an antitussive is to be reckoned with, and a hot lemon and honey drink
that promotes salivation may prove as effective against a sickly cough
as an elaborate opiate syrup. Even a well-spiced curry may induce salivation
and suppress an irritating cough.
Topical decongestants containing oxymetazoline or xylometazoline activate
sympathetic receptors and constrict nasal blood vessels. They may remain
effective for eight to 10 hours and are useful for night-time treatment.
But if used to excess they may induce rebound congestion. Oral decongestants
such as ephedrine, pseudoephedrine and phenylephrine are less effective
against cold symptoms and may induce side effects such as hypertension.
Analgesics such as paracetamol and ibuprofen have a well established
role in relieving symptoms of the common cold. A once popular remedy,
menthol, acts as a local anaesthetic, and at the same time induces the
sensation of decongesting the respiratory system although in fact it
does not have this effect. Menthol does alter breathing patterns, and
so may benefit infants with a night-time sniffle. It apparently suppresses
cough, and may be effective in this regard when applied topically.
Certain substances may be useful in promoting immune reactions to infections
such as that of the cold virus. One is zinc, taken as a food supplement.
Another is echinacea, over which there is controversy, however.
In general, treating a common cold must be a matter of common sense.
Whether the condition cures itself with patience, and whether its course
can be shortened by the many traditional treatments in use is largely
a matter of opinion. The great unknown factor is how far the placebo
effect operates towards the cure.
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For five millennia the marshes that surround the confluence of the Euphrates and Tigris rivers supported the Marsh Arabs of Iraq. But when Saddam Hussein attempted to reorganise the entire region, he nearly destroyed the lives of the inhabitants by creating 32 dam projects upstream and deliberately draining the marshes until they constituted only 5 per cent of their former extent.