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Treatment and prevention of the

common

cold

Professor Graham Worrall, professor of family medicine, looks

at the evidence on managing the scourge of winter, the common cold

Treatment

It cannot be overemphasised that there is no effective treatment for the cold, despite many claims. This is an analysis of the various preparations that people take, often in an attempt to relieve the symptoms rather than cure the illness.

Antitussives

It has been estimated that 75 per cent of us take an antitussive when we get a cold. Nevertheless, despite their ubiquitous presence in the drug stores, there is not much evidence that antitussives work. Trials of the

ingredient agents, such as dextromorphan, codeine and ipratropium, have not been convincing; nor is there evidence that the expectorants, such as guaifenesin, help the patient to get better more quickly.

Antitussives are more effective in adults than in children, and codeine is likely

to have unpleasant side-effects in young

children.

Several extensive reviews of these agents have concluded that the best that can be said for them is that they ease the symptoms of some people until the cold gets better (ICSI, 2001; Schroeder and Fahey, 2002).

Antihistamines

These have been the subject of a number of well-designed studies, but reviewers have concluded that the literature offers little support for the use of antihistamines in the common cold. One well-conducted systematic review by Dr Paul Luks of the MonteRore Medical Center, New York, found that compared with placebo, antihistamines reduced symptoms of runny nose and sneezing for the first two days of both naturally occurring and experimentally induced colds.

Decongestants

A Cochrane review of over-the-counter medications by Dr Knut Schroeder at the University of Dundee found that a single dose of nasal decongestant reduced subjective symptom scores by 13 per cent, but there was no evidence of benefit from repeated use over several days. Nasal sprays or oral decongestants may provide temporary relief.

Another Cochrane review of nasal decongestants for the common cold in adults, by Dr David Taverner at the University of Adelaide, found that there was a 13 per cent reduction in symptom score with decongestants, compared with placebo. There was a significant initial decrease in airways nasal resistance when agents such as oxymetazoline, norepinephrine and pseudoephedrine were used. However, there was no significant decrease in congestion after repeated doses over a five-day period. It is well known that long-term use of nasal decongestants can lead to rhinitis medicamentosa.

Antipyretics/NSAIDs

These have been found to relieve the headaches and sore throats associated with a cold, but not to shorten the illness duration.

Echinacea

Extracts from the echinacea plant are widely used by patients and practitioners in Europe and the USA, both to prevent and to treat

upper respiratory tract infections. In Germany alone there are currently more than 200 preparations on the market that contain echinacea, either alone or in combination with other plant products.

A systematic review by Dr Dieter Melchart and colleagues at the University of Munich found that most trials reported favourable results and, overall, the results suggested that some echinacea preparations may be more effective than placebo. However, the reviewers concluded that as yet there is insufficient evidence to recommend a specific preparation, as the products varied widely in strength and formulation.

Vitamin C

Vitamin C has also been popular in the prevention and treatment of colds, especially since the publication of books by Dr Linus Pauling. There have been two systematic reviews of the vitamin C trials (Douglas et al, 1997; Hermila, 1996). They found there was a consistently modest therapeutic effect, with shortening of the duration of symptoms by about half a day. Some small studies have explored the effect of vitamin C when people are under extreme physical stress (for example, during military training or long-distance running). The vitamin may have a small preventive effect in individuals who are predisposed to recurrent colds.

Zinc

It is known that zinc possesses some antiviral properties in vitro, so the treatment has biological plausibility. Since the publication of the results of a randomised controlled trial of zinc lozenges conducted in 1983 by Dr George Eby and colleagues, which suggested that the treatment could cut the duration of cold symptoms by almost half, there has been much interest in the use of zinc lozenges for the common cold.

Unfortunately, the results of subsequent trials have not been so spectacular. Two reviews of all the zinc trials have been undertaken (Marshall et al, 2001; Garland and Hagmeyer, 1998), and both concluded that evidence for the effectiveness of zinc lozenges in reducing the duration of common colds is lacking. They comment that even if the use of zinc produces a modest reduction in severity and duration of symptoms, it must be weighed against the unpleasant taste of zinc and the need to administer it frequently.

Antiviral agents

There have been many studies of antiviral medications, such as interferon and interferon inducers, for the common cold. Unfortunately, according to a heroic review by Jefferson and Tyrell in 2001, who examined 241 studies, any slight beneficial effect is outweighed by their unpleasant side-effects.

Comfort measures

Mothers around the world have traditionally recommended comfort measures for colds. Humidification of the environment, plentiful warm fluids, a nutritious diet, throat lozenges, salt-water gargles, saline nose drops, elevation of the head of the bed and adequate rest have all been advocated.

Steam inhalation does serve as an effective comfort measure for some people. There have been several trials. A systematic review of six trials supported the use of warm vapour inhalations to relieve symptoms of the common cold (Singh, 2001).

Antibiotics

Reports from the USA, the UK, Australia, New Zealand, the Netherlands, Finland, Italy, Croatia and Taiwan have all shown that GPs prescribe antibiotics for up to half of all patients they see with the common cold. In other countries, patients are able to buy antibiotics for themselves. Although three-quarters of the world's population live in Africa, the Middle East, South America and Asia, these countries together account for only about 20 per cent of the world's antibiotic consumption.

Physicians in the developed world are responsible for most antibiotic prescribing.

A Cochrane review of antibiotics and the common cold, undertaken by New Zealand GP Dr Bruce Arroll, concluded that antibiotics have no effect on the severity or duration of the cold. Most of the nine trials in the review were not conducted in general practice – they used A&E patients, young military recruits or people attending infectious diseases clinics. Of the two trials that were conducted in general practice, neither Dr John Howie's study of men in Glasgow nor Dr John Taylor's study of children aged two to 10 years in general practice in the UK showed any benefits from the use of antibiotics.

Ever since the pronouncement by the 17th-century Sage of Leyden, Gerardus van Swieten, 'Certum est, quod in omnibum pectoris morbis, sputa attentam moreatur considerationem' ('It is certain that, in considering all chest diseases, careful attention must be paid to the sputum'), doctors have been paying far too much attention to sputum and 'snot'.

Many patients, and regrettably also many doctors, still think that green or purulent sputum or nasal discharge is a justification for the use of antibiotics. However, this sign does not mean that a cold needs antibiotics, as it does not discriminate between viral and bacterial infection. Purulence occurs when inflammatory cells or sloughed mucosal cells are present, and can result from either type of infection.

Can colds be prevented?

As it seems clear that colds cannot be cured, much effort has been expended in trying to prevent them. Several studies (none of them well-designed trials) have found that hand-washing is the most effective way to prevent the spread of the common cold, especially at the onset of the illness or when the patient is febrile, when the cold is most contagious.

Echinacea

A review of the many studies of preventive effects of regular administration of echinacea concluded that, despite the generally poor quality of the trials, slightly fewer people had colds when they took the preparation (Melchart, 2002).

Vitamin C

Two reviews of the effects of taking preventive vitamin C found that there was no beneficial effect for most people, although there may be small subgroups (such as competitive athletes and those doing heavy physical work) who might benefit (Douglas et al, 1997; Hermila, 1996).

Ginseng

A recent study conducted in Alberta, Canada, compared people who took two capsules of North American ginseng extract daily for four months during the winter season with controls (Predy et al, 2005). Ginseng appeared to reduce the mean number of colds caught, the proportion of individuals who had more than two colds and the duration of the cold symptoms.

More research is needed to confirm the findings of this study. Whether many people are prepared to take relatively expensive medicines regularly throughout the cough and cold season each year, in the hope of gaining a modest preventive benefit, remains to be seen.

Vaccines

At present there are no effective vaccines for the common cold. Some of the earliest recorded trials of the prevention of common colds tried using vaccines, but found that they were not effective (Scientific Committee on Common Cold Vaccines, 1965; Ferguson et al, 1927).

This is an extract from There's a lot of it about: Acute Respiratory Infections in Primary Care, 2006, by Professor Graham Worrall, professor

of family medicine, family medicine research director and director at the Centre for Rural Health Studies, Memorial University of Newfoundland and Labrador in Canada.

To order a copy (paperback priced £21.95)

e-mail orders@radcliffemed.com

or call 01235 528820

Key points

Treatment

• Antitussives relieve cough in adults more than in children

• There is little support for the use of antihistamines

• Decongestants relieve cold symptoms

• Antipyretics/NSAIDs may relieve fever and headache, but do not affect the clinical course

• Some echinacea preparations may be more effective than placebo

• Vitamin C may reduce duration by about half a day

• Zinc may reduce the duration of a cold slightly, but there is no consistent evidence of benefit

• Comfort measures: steam inhalation relieves symptoms, but there is no good evidence for other comfort measures

• Antibiotics: there is no evidence of effectiveness

Key points

Prevention

• Hand-washing is effective in preventing the spread

of colds

• Echinacea has a possible

small preventive effect

• Vitamin C has no effect in

most people

• Ginseng may have a small effect

• There are no effective vaccines

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