A drug used to treat bone pain caused by cancer makes little difference to patients' well-being, new research shows.
The study is the latest to suggest there is no evidence that pregabalin, which is increasingly being prescribed, works.
Researchers had set out to test whether the drug could reduce bone pain in one in three patients - the threshold that would make it worth prescribing.
More than 200 people were tested in the University of Edinburgh study. Patients were divided into two groups and half were given a placebo - a dummy drug - and half took pregabalin for four weeks. All patients had bone pain without any evidence of the pain being caused by nerves.
No significant difference was found in the pain or quality of life experienced by the two groups throughout the study.
The researchers concluded that although pregablin is increasingly used to treat bone pain caused by cancer, there is no evidence that it is beneficial to the patient.
Bone pain is the most common pain caused by cancer. Radiotherapy can reduce pain but only in around one quarter of patients.
Lead researcher Professor Marie Fallon of the Edinburgh Cancer Research Centre, which is based at the University of Edinburgh, said: ''It is important to find out whether or not pregabalin helps reduce bone pain before it becomes widely used.
"Our study has shown that giving pregablin has no-more effect on pain than a placebo. This suggests it shouldn't be prescribed as a way to control bone pain related to cancer.''
The research, published in the Journal of Clinical Oncology, was funded by Cancer Research UK.