A drug frequently prescribed for pain is no more effective than a placebo at controlling sciatica, a common source of pain in the lower back and leg, according to a study published in the New England Journal of Medicine.

Researchers at the George Institute for Global Health in Australia followed 209 sciatica patients who were randomly assigned to receive either pregabalin, more commonly known as Lyrica, or a placebo.

The results showed no significant differences in leg-pain intensity between the group on the placebo and that on Lyrica after eight weeks taking the drug or during the rest of the year on follow-up exams. Similarly, there were no differences for other outcomes such as back pain, quality of life and degree of disability.

After Lyrica was approved in 2004, it has become the most commonly prescribed medicine for neuropathic pain, which is caused by damage to the nervous system. The drug was ranked as the 19th-highest-earning pharmaceutical in 2015, with worldwide sales rising annually at a rate of 9 percent and U.S. sales of more than $3 billion in 2015.

“We have seen a huge rise in the amount of prescriptions being written each year for patients suffering from sciatica. It’s an incredibly painful and disabling condition, so it’s no wonder people are desperate for relief and medicines such as pregabalin have been widely prescribed,” Christine Lin, one of the authors of the study, said in a news release.

Sciatica can be particularly debilitating and is a symptom of a problem with the sciatic nerve, the largest nerve in the body. In most cases, the cause of the pain remains unclear. Often accompanied by weakness, numbness and tingling, the pain usually radiates on one side of the body and can spread from the lower back to the lower leg and the foot. Sciatic symptoms can subside on their own.

According to the researchers, around 12 percent of the world’s population has lower back pain at any one time, and around 5 to 10 percent of those with such pain have sciatica.

The randomized, double-blind placebo study also found significantly more side effects in people who took Lyrica than in those who were on the placebo. Nearly two-thirds of the participants were very satisfied or satisfied with their drug regimen, regardless of whether they were taking Lyrica or a placebo.

“It seems people associate a drop in pain being due to taking a capsule, rather than something which would happen naturally over time. General practitioners who are prescribing Lyrica should take note of these findings and talk with their patients about other ways of managing and preventing pain,” Lin said.

Lyrica became the best-selling drug for Pfizer after the company’s patent for the statin Lipitor expired in 2012.

Pfizer issued a statement about the study saying, “Lyrica is currently approved in more than 130 countries and regions globally. The efficacy and safety of Lyrica for its approved indications has been demonstrated in large-scale, double blind, randomized, placebo controlled pivotal trials. Lyrica continues to be an important treatment option for the conditions for which it is approved.”