About two-thirds of adults have lower back pain at some point in their lives, and most are told to take acetaminophen, sold under brand names like Tylenol, Anacin and Panadol. Medical guidelines around the world recommend acetaminophen as a first-line treatment.
But there has never been much research to support the recommendation, and now a large, rigorous trial has found that acetaminophen works no better than a placebo.
“Our result illustrates the problems in relying on that indirect evidence when setting guidelines,” said Christopher M. Williams, a researcher at the George Institute for Global Health in Sydney and lead author of the new study, published Wednesday in The Lancet.
Williams and his colleagues randomly assigned 1,643 people with low back pain to one of three groups. The first was given two boxes: one “regular” box containing 500-milligram acetaminophen tablets, and a second “as-needed” box also containing acetaminophen.
The second group received a regular box of acetaminophen and an as-needed box containing a placebo. The third group received two boxes of placebos.
All participants were told to take six tablets every day from the regular box, and up to two tablets a day from the as-needed box for pain relief.
The three-month study found no differences among the groups in recovery time, pain, disability, function, symptom changes, sleep or quality of life. About three-quarters of the patients were satisfied with their treatment whether they received medicine, placebos or both.
Dr. Bart W. Koes, who wrote an editorial accompanying the paper, said that even though the study was large and methodologically sound, it was not necessarily the last word on the subject.
“The fact that it’s no more effective than placebo does not mean that it doesn’t work for a given patient,” wrote Koes, a professor of general practice at Erasmus University Medical Center in Rotterdam, Netherlands.
Williams said acetaminophen had been shown to be effective for headaches, toothaches and pain after surgery, but the mechanism of back pain is different and poorly understood. Doctors should not initially recommend acetaminophen to patients with acute low back pain, he said.
But, he added, “If patients already taking it feel they are getting a benefit, then it wouldn’t be wise to tell them to stop.”
