Acetaminophen no better than placebo for back pain, study finds

Acetaminophen isn't any better at relieving back pain than a fake pill, despite almost universal recommendations to take the drug, according to the first big trial to test it.

Acetaminophen, sold as Tylenol and Paracetamol, among other names, is recommended in numerous guidelines for back pain, mainly because it has few side effects; past studies have shown it works for other types of pain. But there is no proof it is effective for lower back pain in particular.

In a new study, Australian researchers assigned more than 1,600 people with acute lower back pain to either acetaminophen - to a maximum dose of 4,000 mg per day - or a placebo. Scientists found no major difference in the time it took people to recover: Those on acetaminophen got better after 17 days while those who took dummy pills recovered after 16 days. The study focused on the kind of back pain most people experience, resulting from lack of exercise, bad posture, or a strain.

The research was paid for by the Australian government and GlaxoSmithKline Australia. It was published online Wednesday in the journal, The Lancet.

"Most people would have thought (acetaminophen) would have some effect, so this was a surprise," said Bart Koes of Erasmus MC University Center in the Netherlands, who co-authored an accompanying commentary. He said doctors should monitor people taking acetaminophen to see if the drug actually works. If not, they should switch patients to stronger medication while advising them to stay active.

Lower back pain is the leading cause of disability worldwide and doctors usually recommend treatments including painkillers, exercise, stretching, physical therapy and old-fashioned remedies like hot and cold packs.

"The mechanisms of back pain are likely to be different from other pain conditions and this is an area that we need to study more," said Chris Williams of the University of Sydney in Australia, the study's lead author, in an email.

"We know exercise helps so people should stay as active as possible," said Chris Mercer, a physical therapist specializing in back pain and spokesman for Britain's Chartered Society of Physiotherapy. "Don't just take to your bed."

Some doctors said it was too early to give up on acetaminophen and said most people would get better within a week or two whatever treatment they tried.

"Different strategies will work for different patients," said Dr. Nigel Mathers, honorary secretary of Britain's Royal College of General Practitioners. "If (acetaminophen) works for you, then continue to take it."