Although its use is universally recommended to treat people with acute lower back pain, the painkiller acetaminophen -- the active ingredient in Tylenol -- does not speed recovery or reduce pain from the condition, according to a recent study.

Researchers found that the drug - which is the first choice pain killer for lower back pain -- was no more effective than placebo, or dummy, pills for "hastening recovery from acute bouts of low back pain or easing pain levels, function, sleep or quality of life," Reuters reported.

"The results suggest we need to reconsider the universal recommendation to provide [acetaminophen] as a first-line treatment for low-back pain," Christopher Williams, who led the study at the University of Sydney in Australia, said in a statement.

For the study, the research team randomly assigned more than 1,600 individuals with acute low-back pain from 235 primary care centers in Sydney, Australia to receive up to 4 weeks of acetaminophen in regular doses (three times a day; equivalent to 3990 mg per day), acetaminophen as needed (maximum 4000 mg per day), or placebo. All participants received advice and reassurance and were followed-up for 3 months.

Researchers found no differences in the number of days to recovery between the treatment groups. The median time to recovery was 17 days in the group receiving acetaminophen, 17 days in the as-needed acetaminophen group, and 16 days in the placebo group.

The research team said the findings call into question the universal endorsement of acetaminophen as the first choice when treating this common form of back pain.

"Simple analgesics such as [acetaminophen] might not be of primary importance in the management of acute lower back pain," Williams said. "Understanding why [acetaminophen] works for other pain states but not low-back pain would help direct future treatments."

The findings were recently published in The Lancet medical journal.