Few pain specialists advise patients with low back pain to simply “take two aspirin and call me in the morning,” to borrow from a now-ancient phrase. Now research suggests that acetaminophen, a commonly used aspirin alternative for low back pain, may not be effective as well.
A study published online in The Lancet (2014 Jul 23) found that acetaminophen was no more effective than placebo in relieving the symptoms of chronic low back pain when administered in either regular or as-needed dosing schedules. The results actually contradicted the authors’ hypothesis before initiating the project. The new research was designed to follow up on an earlier study, also published in The Lancet (2007;370:1638-1643), that demonstrated that adding other treatments (manipulation and nonsteroidal anti-inflammatory drugs) to the recommended guidelines in Australia of advice, reassurance and regular acetaminophen did not speed recovery or improve low back pain symptoms.
“Because patients in the study recovered faster than expected overall, we hypothesized that taking [acetaminophen] regularly was helping with the patients’ recovery,” the study’s lead author, Chris M. Williams, PhD, a postdoctoral research fellow at The George Institute for Global Health, in Sydney, said in an interview. “This assumption was also based on previous questioning of patients who said they typically only take [acetaminophen] ‘as needed.’ In the current study, though, we didn’t find any evidence to support the use of [acetaminophen], no matter how patients took it.”
The new study enrolled more than 1,600 patients from 235 primary care centers in Australia. As part of the multicenter, double-dummy, randomized, placebo-controlled design, patients with low back pain were randomized to receive up to four weeks of regular doses of acetaminophen (three times per day, equivalent to 3,990 mg per day; n=550), as-needed doses of acetaminophen (taken when needed for pain relief; maximum 4,000 mg per day; n=549) or placebo (n=553). According to the authors, patients and staff at all 235 study sites were blinded to treatment allocation, and all study participants received “best-evidence advice” and were followed for three months.
The authors observed no differences in recovery time among the three groups. They reported that median time to recovery was 17 days in the regular and as-needed acetaminophen groups, and 16 days in the placebo group (P=0.79). The median number of tablets consumed per participant per day was four in the “regular” group, 3.9 in the as-needed group, and four in the placebo group (with a maximum of six tablets allowed per day). The number of patients reporting adverse events was similar among all three groups.
“This study certainly casts some doubts on the common practice of using acetaminophen as the first-line agent for low back pain,” said Maryam Jowza, MD, assistant professor of anesthesiology at Weill Cornell Medical College and a pain specialist at the Weill Cornell Pain Medicine Center, in New York City. Although Dr. Jowza, who was not involved in the research, described the study as “well designed,” she noted that the results might have been influenced by patient adherence to the prescribed regimens (which the authors acknowledged), as well as the use of concomitant treatments by those in the as-needed and placebo groups. “It is still too early to change the clinical guidelines, which recommend using acetaminophen as the first choice,” she said.
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