It appears that spinal injections of etanercept, a new type of anti-inflammatory genetically engineered drug, are not as effective in relieving the severe leg and lower back pain of sciatica, as steroid injections into the spine, the current standard of care, according to a new study reported in the 17 April issue of the Annals of Internal Medicine.
Dr Steven P Cohen, an associate professor of anesthesiology and critical care medicine at the Johns Hopkins University School of Medicine in Baltimore, Maryland led the study.
He told the press pain experts have long been looking for a, safe, reliable alternative to steroids as a way to treat sciatica. The current treatment, where steroids are injected into the spine, often has mixed results and only temporarily relieves pain. It also has the potential for “catastrophic complications”.
Etanercept is a genetically-engineered tumor necrosis factor inhibitor (TNF) that is currently used to treat rheumatoid arthritis and other autoimmune disorders, where the patient’s own immune system attacks healthy tissue, causing damage, pain and swelling.
Cohen said research interest in etanercept, sold under the brand-name Enbrel, arose from attempts to prevent or limit the pain produced by herniated discs pressing on nerve roots in the lower back or neck.
The drug works by blocking TNF, a naturally produced substance that causes inflammation. Unlike steroids that combat inflammation generally, TNF inhibitors target the specific inflammation molecules that cause the pain from sciatica and other conditions. They do this by stopping them being able to bind to nerve cell receptors, which should in theory prevent pain altogether.
However, Cohen said while this new treatment shows a lot of promise, “at least in the doses we gave it – the dose known to be safe – steroids still work better”.
For the blinded, placebo-controlled study, 84 adult patients with sciatica (lumbosacral radiculopathy) of less than 6 months’ duration received epidural injections. The patients were randomly assigned to receive either 60 milligrams of a steroid, 4 milligrams of etanercept, or 2 milliliters of saline.
The idea behind giving sciatica patients an epidural injection is to provide better pain relief at lower doses, and fewer side effects compared with giving drugs by mouth or intravenously, because the spinal nerve roots are bathed directly in the medication designed to reduce inflammation (and pain).
The trial ran from 200 to 2011 and took place at several military and civilian treatment centers. Pharmacists prepared the epidural syringes, while neither the physicians who administered the injections, nor the nurses who assessed the outcomes, knew which patient received which treatment.
The results showed that one month after receiving the second of two injections, the patients who received steroids reported less pain and disability than the patients who received etanercept or the saline placebo.
However, Cohen and colleagues found that while the steroids worked, their effect did not last.
Cohen comments that another study published last month, where patients received more than twice the dose of etanercept used in their study, found one and two weeks after injection, the etanercept patients felt better than the patients given steroids, but not four weeks after.
It could be that in lower doses, “etanercept may not be the drug everyone’s hoping it is”, says Cohen, noting that “There’s still a lot more work to be done”.
He suggests there is a need to investigate the safety and effectiveness of higher doses of etanercept and other drugs that block pain receptors.
Most of the funds for the study came from the John P. Murtha Neuroscience and Pain Institute, the International Spinal Intervention Society and the Center for Rehabilitation Sciences Research.
Written by Catharine Paddock PhD