The drug injections also didn't increase the risk of infection and other complications, despite some previous safety concerns.

It's possible, researchers said, that higher doses of steroids or the anti-arthritis drug etanercept (marketed as Enbrel) may do a better job of easing pain in this notoriously hard-to-treat group of patients. Or people might get more pain relief if the shots are given as-needed, instead of at set intervals.

So the findings can't say definitively whether or not either type of injection might help some people with nerve-related chronic pain, researchers report in the Annals of Internal Medicine.

"This kind of pain is very challenging to treat. There's no reliable treatment that works in everyone," said Dr. Steven Cohen from the Johns Hopkins University School of Medicine in Baltimore, who worked on the study.

Medications tend not to work very well, he told Reuters Health. And although surgery may help in the short term, studies haven't found an effect in people who did or didn't have an operation a couple of years down the line.

Most people with lower back and leg pain due to nerve damage -- also known as sciatica -- are treated with epidural steroid injections, Cohen said. But recently, there's been more interest in injections of immune-suppressing drugs like etanercept.

"People are looking for something more effective and something safer," he said.

"The findings are disappointing, but by no means is this the end of the story."

LACK OF EFFECT FOR EXPENSIVE DRUGS

Cohen's study involved 81 people who'd had sciatica for at least a month. The patients were in their early 40s, on average, and treated at one of four military medical centers and two civilian hospitals.

Study participants were split into three treatment groups. They were given two spinal injections, two weeks apart, of the steroid methylprednisolone, etanercept, or normal salty water, called saline. Neither the patients themselves nor the doctors treating them knew who got which type of injection.

At check-ins one month later, patients' back and leg pain was reduced by a similar amount, regardless of which treatment they'd received. Their back pain scores fell by average of one to two points, and leg pain by two to four points, on a 10-point scale.

People who had gotten steroid or saline injections reported bigger improvements in how well they could get around and perform usual activities compared to those in the etanercept-injection group.

The lack of any significant benefit with etanercept, compared to normal saline, was "disappointing," according to Cohen. "These drugs are expensive, and even though they may be safer than steroids, they're not devoid of risk," he said.

Steroid or etanercept injections cost about $500 to $700 each, Cohen said. The biggest concern with etanercept is immune system side effects, he added, while steroids can cause stomach problems and alter blood sugar levels.

Between one and six patients in each group had side effects related to the injections, including worsening pain, a rash or infection, but none were serious.

It's possible that patients treated with regular saline got some relief because the injection washed out the spine and increased blood flow to nerve roots, researchers said.

In the end, whether or not patients' sciatica pain improves may be more up to their own behavior than what type of injections they get, if any, Cohen added.

"The treatment that has the strongest evidence behind it is actually exercise programs," he said -- as well as losing weight, for people who are too heavy.

"It's kind of a long, slow process. People have to have realistic expectations."

SOURCE: bit.ly/atTzv0 Annals of Internal Medicine, online April 16, 2012.

• A Permanent Economic Emergency