By Pat Anson, Editor

The world’s most widely used over-the-counter pain reliever is ineffective in treating low back pain and provides little benefit to people with osteoarthritis, according to a new study published in the British Medical Journal.

In a systematic review of a dozen research reports (a study of studies), Australian researchers also questioned many of the conventional treatments for back pain and other musculoskeletal conditions.

Acetaminophen -- also known as paracetamol – is the active ingredient in Tylenol, Excedrin, and hundreds of other pain medications. It is often recommended by doctors worldwide for back pain and osteoarthritis.

"Clinicians should carefully weigh benefits and harms when making treatment decisions. Paracetamol is not efficacious and potentially harmful. In this context we cannot justify its continued use for these prevalent diseases,” said Professor David Hunter of the University of Sydney.

The researchers found “high quality” evidence showing that patients taking acetaminophen are at greater risk of liver toxicity and nearly four times more likely to have abnormal results from liver function tests.

"World-wide, paracetamol is the most widely used over-the counter medicine for musculoskeletal conditions so it is important to reconsider treatment recommendations given this new evidence," said lead author, Gustavo Machado of The George Institute and the University of Sydney.

Low back pain is the leading cause of disability worldwide, and osteoarthritis of the hip or knee is the 11th highest contributor to global disability.

"This latest research, the most comprehensive systematic review of its kind, reaffirms this with an even larger, global patient base, and has for the first time also established that the effects of paracetamol for knee and hip osteoarthritis are too small to be of clinical importance." said senior author Manuela Ferreira of the George Institute for Global Health and the University of Sydney.

"We urgently need to take stock of the evidence for common musculoskeletal conditions, a largely under-recognized health priority, and make sure people are receiving appropriate care."

Treatments known to be effective for low back pain include counseling, physical therapy, exercise and psychological therapies such as cognitive behavioral therapy.

Aerobic exercise, strengthening exercise, weight management and anti-inflammatory medicines have been shown to provide benefit for patients with lower limb osteoarthritis.

A recent study published in The Lancet found that acetaminophen had no effect on pain, disability, function, sleep quality, or quality of life for people with low back pain.

Over 50 million people in the U.S. use acetaminophen each week to treat pain and fever. The pain reliever has long been associated with liver injury and allergic reactions such as skin rash. In the U.S. over 50,000 emergency room visits each year are caused by acetaminophen, including 25,000 hospitalizations and 450 deaths.