Analgesic Efficacy Altered by Patient Beliefs

Subjective pain relief and pain-related brain activity affected by patient expectations

THURSDAY, Feb. 17 (HealthDay News) -- An individual's expectation of a drug's effect influences both its therapeutic efficacy and the pain-related brain pathways that are activated during treatment, according to a study published in the Feb. 16 issue of Science Translational Medicine.

Ulrike Bingel, M.D., of the University of Oxford in the United Kingdom, and colleagues investigated how patients' expectations of an analgesic's effectiveness impact their subjective experience of pain. Healthy participants were exposed to pain-provoking heat and given the opioid remifentanil. Some people were told that the drug would have no effect; some were told that it would diminish their pain; and some were told it would worsen their pain. The researchers also used functional magnetic resonance imaging (fMRI) to observe brain activity in the different scenarios.

The researchers found that individuals who expected pain relief experienced twice as much analgesia as people who expected no pain relief. Individuals who were told that the drug would aggravate their pain obtained no analgesia from remifentanil, describing their subjective pain as unchanged. Using fMRI, the researchers observed differences in neural activity in the brain regions that take part in coding pain intensity. Individuals who expected positive results from the analgesic showed brain activity in the endogenous pain modulatory system; whereas, individuals with negative expectations about the drug showed more activity in the hippocampus.

"We propose that it may be necessary to integrate patients' beliefs and expectations into drug treatment regimes alongside traditional considerations in order to optimize treatment outcomes," the authors write.

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