fMRI Could Help Identify New Painkillers

Measuring the brain's neural response to pain using functional magnetic resonance imaging (fMRI) may be a viable tool for evaluating the effectiveness of new pain medications, according to a new study.

Researchers at John Radcliffe Hospital (Oxford, United Kingdom) and Oxford University (United Kingdom) conducted a double-blind, randomized study in 24 healthy volunteers on three separate occasions to assess the use of fMRI in obtaining objective outcome measures of drug differentiation. To induce pain, the researchers used capsaicin cream, a topical irritant often used to produce similar characteristics of neuropathic pain on subjects' skin.

Prior to capsaicin cream application, the subjects either received a single dose of gabapentin, which is considered effective and a first line treatment for neuropathic pain; ibuprofen, which is generally not considered an effective treatment for the condition; or a placebo. The researchers then assessed the effect the drugs or placebo had on the brain's neural response to pain using fMRI, in addition to patient-reported pain relief.

The results showed that neural activity was significantly reduced in the subjects who received gabapentin, even with extremely low subject numbers, highlighting the potential for fMRI to make a drug's effect clear in small cohorts, such as during the early stages of human drug development. This ability could provide a much-needed objective method to collect data that could prevent premature discarding of potentially beneficial therapies. The study was published in the January 2106 issue of Anesthesiology.

“Chronic pain is a very common condition. Even the most effective pain medications currently available only provide adequate pain relief, defined as a 50% reduction in pain, in one out of four patients, while some drugs, such as opioids, have significant side effects, including dependence and overuse,” said lead author Vishvarani Wanigasekera, MD, of the University of Oxford. “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.”

Patient-reported pain relief is the primary outcome measure used in current drug development studies to assess whether medication is effective or not. However, due to their subjective and context-dependent nature, self-reported pain perception and relief are subject to many influences. Due to the low subject population, researchers can also easily miss effective compounds that might work well in the population at large.

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John Radcliffe Hospital
Oxford University