Even though its use is often advised by doctors, the painkiller acetaminophen -- best known as Tylenol -- does not help treat lower back pain, according to a new Australian study.
The researchers found the drug was no more effective than a dummy pill for more than 1,600 people suffering from acute lower back pain.
The research team said the findings call into question the belief that acetaminophen should be the first choice when treating this common form of back pain.
The drug "might not be of primary importance in the management of acute lower back pain," study lead author Dr. Christopher Williams from the George Institute for Global Health at the University of Sydney in Australia, said in a news release from the journal The Lancet.
The study was published online in the July 23 issue of the journal.
However, one expert said it's probably too early to abandon acetaminophen for lower back pain.
"While this is a fascinating study, it is only one study and shouldn't change clinical behavior," said Dr. Houman Danesh, director of Integrative Pain Management and assistant professor of anesthesiology at The Mount Sinai Hospital in New York City.
For its part, McNeil Consumer Healthcare, which makes Tylenol, said doctors need to consider "the entire body of scientific evidence when making recommendations or changing guidelines." The company said that "the safety and efficacy profile of acetaminophen is supported by more than 150 studies over the past 50 years."
The new study involved more than 1,650 people averaging 45 years of age. All had suffered lower back pain and were treated at 235 different primary care facilities throughout Sydney. Each person was randomly assigned to take either three doses of acetaminophen daily (a total of 3,990 milligrams) for up to four weeks, or a placebo pill.
The researchers pointed out the maximum daily dose of the drug is 4,000 milligrams (mg).
All of the patients received follow-up "reassurance and advice" from a doctor for three months.
According to the study, there were no differences in the amount of time it took any of the patients involved in the study to feel better. The median time to recovery for those taking acetaminophen was 17 days, compared to 16 days for patients in the placebo group.
The drug also appeared to have no effect on the patients' level of pain, compared to people who took the dummy pill, the researchers noted. Acetaminophen also did not improve patients' level of disability, sleep quality or quality of life. About the same number of patients in each group experienced negative health issues, the study found.
The researchers suggested that the medical reassurance the patients received during the study -- something many won't get in a "real world" setting -- could have had a more significant effect on their lower back pain than the medication.
"It would be interesting to see whether advice and reassurance [as provided in our trial] might be more effective than pharmacological strategies for acute episodes of low-back pain," Williams said.
Another expert agreed that encouragement and counseling can be key.
Everyone involved in the study received ongoing " 'good-quality advice and reassurance,' which appears to be a big factor in recovery," said Dr. Michael Mizhiritsky, a physiatrist and specialist in pain relief at Lenox Hill Hospital in New York City.
"In my opinion, positive reinforcement about treatments -- including medications and physical therapy -- in the management of low back pain is vital to a quicker and successful recovery," he added.
Both Danesh and Mizhiritsky also took issue with some of the study's methods.
"The drawback I see is there was no group that did not receive any treatment -- meaning there could be a placebo effect" at work, Mizhiritsky said.
And Danesh said people could still get relief from acetaminophen/Tylenol -- just not the kind of relief outlined in the study.
"The criteria was to be pain-free for seven continuous days when using Tylenol," he pointed out. "It does not address if Tylenol will give you a few hours of relief or a few days."
In the meantime, the prognosis for most people with lower back pain is actually quite good, Danesh stressed.
"Most back pain patients improve in 6-8 weeks," he said. "It is important to note that the best treatment of back pain involves not only pain medication, but also physical therapy to address muscle imbalances. Acupuncture for back pain has also been researched by the U.S. National Institute of Health, and after reviewing the literature they state that there is evidence to support the use of acupuncture for back pain."
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The study was partially funded by drug maker GlaxoSmithKline Australia. HealthDay reached out for comment to McNeil Consumer Healthcare, the makers of Tylenol, but did not receive a reply.