The findings contradict the first line recommendation of doctors for managing back pain and the packaging advice of paracetamol manufacturers.
They startled the University of Sydney researchers who undertook the study upon discovering that there had never been a large-scale trial comparing paracetamol to placebo for back pain.
Back-pain treatment guidelines universally recommend paracetamol as an analgesic.
Panadol sells a product that is dedicated to back and neck pain, containing 500g paracetamol.
"Patients often said, 'I've tried paracetamol and it doesn't seem to work'," said Chris Maher, a professor at the University of Sydney's George's Institute for Global Health.
[Original article: Sydney Morning Herald]