Codeine may not work for cough

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. 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. Researchers from the South Manchester University Hospital Trusts, USA, 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, the 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. 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 above findings are consistent with the view that any anti-cough effect of codeine is attributable to a placebo effect. However, further studies of cough in other clinical situations are needed if codeine is to continue to be used as a cough remedy.