The antitussive effect of placebo treatment on cough associated with acute upper respiratory infection.
OBJECTIVE
The objective of this study was to determine the effects of a placebo treatment on cough in patients with cough associated with acute upper respiratory tract infection (URTI).


METHODS
Patients with dry or slightly productive cough associated with a history of URTI were recruited. Cough frequency (CF) over 15 minutes was recorded by means of a microphone connected to a pen recorder. Cough suppression time (CST) was recorded when patients were instructed by means of a red light to try not to cough. Patients received either a single dose of vitamin E (placebo treatment) or no treatment. CF and CST were recorded before and 15 minutes after treatment.


RESULTS
Twenty-seven patients were randomized to placebo treatment and 27 to the no-treatment group (mean age 22.6 years). The median difference between post- and pretreatment CF was -3 in the no-treatment group and -18 in the placebo group (p = .0003). There was a significant increase in CST in the placebo group compared with no treatment (p = .027).


CONCLUSIONS
The results demonstrate that placebo treatment has significant antitussive activity. This placebo effect may be related to generation of central neurotransmitters such as endogenous opioids.
Lee
Patrick C L
PC
Common Cold Centre, Cardiff School of Biosciences, Cardiff University, Cardiff CF1 3US, UK.
Jawad
Mutaz S M
MS
Hull
J David
JD
West
Will H L
WH
Shaw
Kerry
K
Eccles
Ron
R
D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000368:Aged; D000996:Antitussive Agents / Q000627:therapeutic use; D003371:Cough / Q000188:drug therapy* / Q000209:etiology / Q000517:prevention & control; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015990:Placebo Effect; D010919:Placebos / Q000008:administration & dosage / Q000627:therapeutic use*; D012141:Respiratory Tract Infections / Q000150:complications* / Q000523:psychology; D016896:Treatment Outcome; D014810:Vitamin E / Q000008:administration & dosage / Q000627:therapeutic use
D000996:Antitussive Agents; D010919:Placebos; D014810:Vitamin E