Opioid Efficacy and Dosing Due for More Clinical Trials

May 31, 2016

Researchers assess the efficacy of opioids for short-term back pain relief.

Opioids can provide modest, but not clinically relevant, short-term pain relief in patients with chronic low back pain, a new study finds.

"Our review challenges the prevailing view that opioid medicines are powerful analgesics for low back pain. Opioid analgesics had minimal effects on pain, and even at high doses the magnitude of the effect is less than the accepted thresholds for a clinically important treatment effect on pain," wrote researchers who were led by Andrew McLachlan, Ph.D., of the University of Sydney in Australia and the George Institute for Global Health in Sydney.

The study appears in the May 23 issue of JAMA Internal Medicine.

More than half of patients prescribed opioid analgesics in the United States have chronic low back pain. In Australia, the three most commonly prescribed drugs for back pain are opioid analgesics or opioid analgesic combinations: oxycodone (11.7%), tramadol (8.2%), and paracetamol and codeine combination (12.1%) (percent of all prescribed medicines for back pain), researchers reported. [[{"type":"media","view_mode":"media_crop","fid":"49030","attributes":{"alt":"©Burlingham/Shutterstock.com","class":"media-image media-image-right","id":"media_crop_2909255688528","media_crop_h":"0","media_crop_image_style":"-1","media_crop_instance":"5895","media_crop_rotate":"0","media_crop_scale_h":"0","media_crop_scale_w":"0","media_crop_w":"0","media_crop_x":"0","media_crop_y":"0","style":"font-size: 13.008px; line-height: 1.538em; float: right;","title":"©Burlingham/Shutterstock.com","typeof":"foaf:Image"}}]]

“Despite the widespread use of opioid analgesics for people with low back pain, there remains uncertainty about three central issues that would guide rational prescribing of these medicines for the treatment of people with low back pain,” researchers wrote. These issues include:

- Uncertainty regarding the efficacy of opioid analgesics for people with acute low back pain.

-  Uncertainty regarding the long-term use of opioids for chronic low back pain.

-  Uncertainty regarding the optimal dosing of opioid analgesics. “There has been little consideration of the extent to which an unselected group of opioid-naive people with low back pain would tolerate or respond to an opioid medicine.”

In this study, researchers found that opioids provided short-term modest pain relief for people with chronic low back pain. It is not known how well it works long-term, nor do physicians or researchers know how well opioids work in acute low back pain.

The researchers analyzed placebo-controlled randomized clinical trials on opioids and low back pain with short-term pain relief (three months or less) as the primary outcome. They found 20 trials with 7,295 participants between them that fit the inclusion criteria. The researchers converted the pain measurements used in the studies (which had scales of either 0 to 100 to 0 to 10) to a 0 to 100 scale.

Thirteen of the studies focused on chronic low back pain. These revealed a modest short-term improvement in pain due to single-ingredient opioids (Mean difference -10.1 on the pain scale; 95 percent CI, -12.8 to -7.4). Six studies showed that single-ingredient opioids improved pain in the intermediate term of greater than three months but fewer than 12 months (Mean difference -8.1; 95 percent CI, -10.2 to -6.0). There was minimal evidence regarding the use of a tramadol paracetamol combination, the researchers wrote. One trial found a mean difference of -8 (95 percent CI, -16.2 to 0.2). 

The threshold for a clinically important outcome was 20 points on the pain scale, met by none of the single-ingredient opioids or combination therapies. A look at the morphine-equivalent dose range of opioids found a 12-point greater pain relief for every 1 log unit increase in dosage (p=.046), but still no clinically relevant effects up to 240 mg morphine-equivalent per day.

 

References:

Shaheed CA, Maher CG, Williams KA, Day R, Mclachlan AJ. Efficacy, Tolerability, and Dose-Dependent Effects of Opioid Analgesics for Low Back Pain. JAMA Internal Medicine. Published online May 23, 2016. doi:10.1001/jamainternmed.2016.1251