A study published this week in the journal Lancet concluded that acetaminophen, the drug found in Tylenol, is no better than a placebo or a dummy pill when it comes to alleviating lower back pain, or improving pain levels, sleep or overall quality of life.

Conducted at hundreds of clinics in Sydney, Australia, the study tracked 1,652 individuals with lower back pain for four weeks. They were given either paracetamol (what acetaminophen is known as overseas), or a placebo. In the end, researchers found there was almost no difference in the number of days required to recover between the two groups; the median time to recovery was 17 days in the regular paracetamol group, 17 days in the as-needed paracetamol group, and 16 days in the placebo group.

“Simple analgesics such as paracetamol might not be of primary importance in the management of acute lower back pain”, said Dr. Christopher Williams from the George Institute for Global Health at the University of Sydney in Australia and the lead author of the study.

“The results suggest we need to reconsider the universal recommendation to provide paracetamol as a first-line treatment for low-back pain, although understanding why paracetamol works for other pain states, but not low-back pain, would help direct future treatments,” he said.

Low-back pain is the leading cause of disability worldwide and is big business for pharmaceutical companies. A 2011 report from the Institute of Medicine found that chronic pain effects about 100 million adults and cost the United States $635 billion each year in medical treatment and lost productivity.

A separate report in 2011 from Decision Resources, one of the world’s leading research and advisory firms for pharmaceutical and healthcare issues, found that therapies to treat chronic back pain and arthritis will continue to be the most lucrative segments of the $20 billion chronic pain drug market through 2020 in the United States, France, Germany, Italy, Spain and Japan.

The makers of Tylenol, McNeil Consumer Healthcare, said in a statement about the study Thursday that it was important to examine “the entire body of scientific evidence when making recommendations or changing guidelines.”

“The safety and efficacy profile of acetaminophen is supported by more than 150 studies over the past 50 years and we are committed to furthering research and education to ensure consumers can make informed choices about their medications,” it said. “Tylenol (acetaminophen) has been providing consumers effective over-the-counter pain relief for decades.”

GlaxoSmithKline, which provided funding for the study and makes Panadol, which includes paracetamol, said it did not expect the findings to bring any changes in the current recommendations “that paracetamol should remain a first line analgesic in low back pain.”

“The study adds to our understanding of how best to manage acute low back pain, highlighting the importance of advice and reassurance to patients suffering from low back pain in improving time to recovery,” the company said in a statement.

Responding to the study in a comment section of the Lancet, Bart Koes and Wendy Enthoven from Erasmus MC, University Medical Center in Rotterdam, Netherlands, agreed that the current treatment recommendations should remain in place.

“Williams and colleagues are to be applauded for tackling this research question on a topic that has been without debate and evidence for such a long time,” they said. “Although the findings from this high-quality trial are clear, the content of guidelines should not be changed on the basis of a single trial; more robust and consistent evidence, including verification of the results in other populations, is needed.”

Not only has the efficacy of acetaminophen been called into question, but prescription products containing it have faced scrutiny from the Food and Drug Administration earlier this year.

It recommended in January that health care professionals discontinue prescribing and distributing products that have more than 325 milligrams of acetaminophen per tablet, contending that there was no data showing that it “provides additional benefit that outweighs the added risks for livery injury.”

It went onto say that limiting the amount of acetaminophen will reduce the risk of severe liver injury from inadvertent overdose, which can lead to liver failure, liver transplant and even death.

This story was updated to include information that the FDA announcement related to prescription products containing acetaminophen.