Paracetamol is ineffective at treating back pain and osteoarthritis despite being a recommended treatment, a group of Australian researchers has warned.
Their review of 13 clinical trials, published in the British Medical Journal, said the drug did not reduce disability or improve quality of life.
Instead, the group warned, it increased the odds of liver problems.
The NHS is to review its guidelines. Experts say patients should consult a doctor before changing medicines.
Back pain is a leading cause of disability and in the UK alone it is estimated to affect 26 million people each year.