Review Article
The Powerful Placebo in Cough Studies?

https://doi.org/10.1006/pupt.2002.0364Get rights and content

Abstract

Placebo treatment has been reported to improve subjective and objective measures of disease in up to 30–40% of patients with a wide range of clinical conditions. A review of 8 clinical trials on the effects of antitussive medicines on cough associated with acute upper respiratory tract infection shows that 85% of the reduction in cough is related to treatment with placebo, and only 15% attributable to the active ingredient Treatment with a cough medicine can be viewed as consisting of three components: pharmacological, physiological (demulcent) and placebo. The placebo effect is related to belief in the effectiveness of the treatment and this idea must in some way influence the central control of cough. Studies on the placebo effect of analgesics indicate that the placebo effect may be mediated by endogenous opioid neurotransmitters and this may explain the analgesic potency of opioid medicines such as morphine. In the present paper a model is proposed to explain the antitussive effects of placebo treatment on the basis of endogenous opioid neurotransmitters. With active pharmacological ingredients contributing only 15% to the effects of cough treatment it seems reasonable to conduct more research on the other components of treatment such as placebo.

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      Citation Excerpt :

      The relationship between a high urge-to-cough threshold and aspiration-related lung infection needs to be investigated. Cough is additionally subject to strong placebo or suggestive suppression, mediated by cognitive processes in the higher brain.31-33 The major function of cough is to engage high-velocity airflow to clear the airways.

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    Author for correspondence: Prof R. Eccles, Common Cold Centre, Cardiff School of Biosciences, Cardiff CF10 3US, UK. E-mail:[email protected]

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