"Not only did theobromine prove more effective than codeine, at the doses used it was found to have none of the side effects."

The research team discovered that theobromine, a derivative found in cocoa, is nearly a third more effective in stopping persistent coughs when compared with codeine, currently considered the best cough medicine.

Better Quality of Life

Professor Peter Barnes, from Imperial College London and Royal Brompton Hospital, and one of the paper's authors, comments: "Coughing is a medical condition which affects most people at some point in their lives, and yet no effective treatment exists. While persistent coughing is not necessarily harmful it can have a major impact on quality of life, and this discovery could be a huge step forward in treating this problem."

The researchers from Imperial College London, Royal Brompton Hospital, St. Bartholomew's Hospital and Chinoin Co. Ltd, Budapest, gave 10 healthy volunteers theobromine, a placebo or codeine at different times in a randomised double blind trial.

To compare the effectiveness of each they measured the levels of capsaicin in the volunteers and compared these after giving the three options. Capsaicin is used in clinical research to cause coughing, and is used as an indicator to test the effectiveness of cough medicines.

When the volunteers were given theobromine, the concentration of capsaicin required to produce a cough was around one third higher when compared with the group receiving a placebo. When the group received codeine they needed only marginally higher levels of capsaicin to produce coughing, compared with the placebo.

Theobromine works by suppressing vagus nerve activity, which is responsible for causing coughing.

No Adverse Effects

The team also discovered that unlike standard cough treatments, theobromine caused no adverse effects on either the cardiovascular or central nervous systems.

Professor Maria Belvisi, from Imperial College London and Royal Brompton Hospital, and one of the paper's authors, comments: "Not only did theobromine prove more effective than codeine, at the doses used it was found to have none of the side effects. Normally the effectiveness of any treatment is limited by the dosage you can give someone. With theobromine having no demonstrated side effects in this study it may be possible to give far bigger doses, further increasing its effectiveness.

"At the same time, theobromine may not have any of the side effects such as drowsiness. This means there will be no restrictions on when it can be taken. For example, people using heavy machinery or who are driving should not take codeine, but they could take theobromine."