Objectives: To review the seven Cochrane reviews of non-antibiotic treatment for the common cold.
Methods: Each Cochrane review was read and summarized, and results presented as relative risks and, where possible, numbers needed to treat.
Results: The main theme that runs through these Cochrane reviews is the variable quality of the primary studies. In general, the reviewers are fairly cautious about the benefits of any of the treatments other than first-dose decongestants and antihistamine-decongestant combinations. For antihistamines alone, the reviewers were clear about the lack of efficacy except in the high-quality studies in which a global improvement in symptoms was noted. Some studies were statistically significant, but the Cochrane reviewers were guarded about how clinically significant they were. For Echinacea, problems were found with the quality of the studies and the wide range of different forms of this substance. Heated humidified air seemed to be effective in the UK and Israel, but not the USA, making definitive statements about efficacy difficult. Over-the-counter medication for cough seemed to have no documented benefit in children under the age of 5 years. Letosteine (a mucolytic) may be effective in children but is not available in the UK. Bisolvon (a mucolytic) was found to be effective for cough in only one study. For older children and adults, dextromethorphan may be effective (two out of three studies showed benefit), and guiafenesin (an expectorant) showed mixed benefit in two trials. Dexbrompheniramine (a sedating antihistamine)/pseudoephedrine (6 mg/120 mg twice daily for 1 week) was significantly more effective than placebo for severity of cough, whereas, in another study, loratadine (a non-sedating antihistamine)/pseudoephedrine (5 mg/120 mg twice daily for 4 days) did not show any difference between the study groups. Vitamin C may have a small role in preventing the common cold, with possibly a greater role in high-intensity physical activity and sub-arctic conditions. Zinc lozenges seemed to be effective, but the issue of unblinding due to taste was a methodological issue of concern to the reviewers. The benefits and harms are calculated as numbers needed to treat for one person to benefit (NNTB) and numbers needed to treat for one person to harm (NNTH), and were calculated by the author.
Conclusion: Most non-antibiotic treatments for the common cold are probably not effective. The most promising are dextromethorphan, bisolvon and guiaphenesin for cough, antihistamine-decongestant combinations for a wide range of symptoms, nasal decongestants (at least for the first dose) and possibly zinc lozenges.