The effect of treatment expectation on drug efficacy: imaging the analgesic benefit of the opioid XXXX .

@entity1 @entity1931 @entity1337 @entity158 @entity1937
Evidence from behavioral and self-reported data suggests that the @entity1 ' beliefs and expectations can shape both therapeutic and adverse effects of any given drug. We investigated how divergent expectancies alter the analgesic efficacy of a potent opioid in healthy volunteers by using brain imaging. The effect of a fixed concentration of the  -opioid agonist @entity1937 on constant @entity158 was assessed under three experimental conditions using a within-subject design: with no expectation of @entity1337 , with expectancy of a positive analgesic effect, and with negative expectancy of @entity1337 (that is, expectation of @entity1931 or exacerbation of @entity158 ). We used functional magnetic resonance imaging to record brain activity to corroborate the effects of expectations on the analgesic efficacy of the opioid and to elucidate the underlying neural mechanisms. Positive treatment expectancy substantially enhanced (doubled) the analgesic benefit of @entity1937 . In contrast, negative treatment expectancy abolished @entity1937 @entity1337 . These subjective effects were substantiated by significant changes in the neural activity in brain regions involved with the coding of @entity158 intensity. The positive expectancy effects were associated with activity in the @entity158 modulatory system, and the negative expectancy effects with activity in the hippocampus. On the basis of subjective and objective evidence, we contend that an individual's expectation of a drug's effect critically influences its therapeutic efficacy and that regulatory brain mechanisms differ as a function of expectancy. We propose that it may be necessary to integrate @entity1 ' beliefs and expectations into drug treatment regimes alongside traditional considerations in order to optimize treatment outcomes.
