Codeine is a standard ingredient in cough remedies, but it seems to be no more effective than an inactive "placebo" compound, at least in people with chronic lung disease, UK researchers report.Dr. Jacyln Smith of South Manchester University Hospital Trusts and colleagues note that codeine is the standard anti-cough agent to which others are compared.Laboratory studies suggest it is effective for cough due to different causes, but little is known about its impact on cough in people with chronic obstructive pulmonary disease (COPD) such as emphysema.To investigate further, the researchers conducted a controlled study of 21 such patients who complained of cough. The participants were challenged with citric acid to induce cough and then, on two separate occasions, they were given either codeine or placebo 1 hour before returning home. There they wore a lapel microphone to record the sounds of "explosive" coughing during the day and night. At the start of the study, they subjects experienced an average of 8.27 seconds of coughing per hour. After placebo treatment this fell to 7.22 seconds per hour. After codeine, it dropped to 6.41 seconds per hour, the investigators report in the Journal of Allergy and Clinical Immunology.Although the time spent coughing was significantly less after codeine than at the beginning of the study, there was no difference between codeine and placebo from a statistical standpoint -- despite the fact that the dose of codeine used "far exceeds that in over-the-counter cough remedies," the researchers note.They conclude that the findings are "consistent with the view that any (anti-cough) effect of codeine is attributable to a placebo effect." Smith and colleagues say that studies of cough in other clinical situations are "urgently needed" if codeine is to continue to be used as a cough remedy.