Identifying New Effective Painkillers for Patients With Chronic Pain

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Functional MRI may help clinicians with identifying new and effective pain medicines for patients with chronic pain.
Functional MRI may help clinicians with identifying new and effective pain medicines for patients with chronic pain.

Functional MRI (fMRI) may help clinicians with identifying new and effective pain medicines for patients with chronic pain, according to a study published in Anesthesiology.

It is current practice for researchers to use patient-reported pain relief as the primary outcome measure in development studies designed to determine whether a painkiller is effective. This approach, however, is subject to many unwanted influences: self-reported pain perception and relief is subjective. Effective compounds that might work well in the general population can be overlooked.

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"Many potential pain relieving drugs identified in preclinical research fail to reach the market because of a lack of early objective evidence that shows whether a drug is effectively reaching target pain receptors in the body and regulating chronic pain mechanisms," Vishvarani Wanigasekera, MD, study author and clinical post-doctoral research fellow at Nuffield Division of Anaesthetics, University of Oxford, England, said in a statement. "We have used noninvasive fMRI to successfully obtain such evidence that we hope can help to prevent the premature discarding of potentially effective pain relievers, as well as avoid exposing patients to ineffective ones."

On 3 separate occasions, the researchers induced central sensitization and some symptom-like features of neuropathic pain in 24 volunteers by applying capsaicin cream on the subjects' skin. The scientists gave study participants either a single dose of gabapentin, ibuprofen, or a placebo prior to capsaicin cream application. The researchers then used patient reported pain relief and fMRI to assess the effect the drugs or placebo had on the brain's neural response to pain.

Only gabapentin reduced pain relevant neural activity. Detected with probability ≥ 0.8, there was a significant difference between placebo and gabapentin. This reduced to less than or equal to 0.6 when using subjective pain ratings.

"There is a clear need for more effective, safer pain relievers," Dr Wanigasekera said. "We believe that neuroimaging techniques, such as fMRI, can provide objective evidence that can be used as outcome measures in early drug development to enhance the efficiency of the drug development process."

Reference

Wanigasekera V, Mezue M, Andersson J, Kong Y, et al. Disambiguating Pharmacodynamic Efficacy from Behavior with Neuroimaging. Anesthesiology, 2016; 124 (1): 159 doi: 10.1097/ALN.0000000000000924.

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