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Examples of Contributions of fMRI on Analgesics |
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| STUDY FOCUS |
REFERENCE |
MAJOR FINDINGS |
COMMENT |
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| Opioids |
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| Remifentanil(short acting μ opioid) |
Wise et al., 2004. [101] |
Activation measured in insula to noxious stimulus in subjects receiving Rx. |
Study evaluates time course and half life of action of Rx in brain region. |
| Remifentanil |
Wise et al., 2002 [102] |
Activation in brain regions to noxious heat stimulus in patients receiving Rx vs. saline. Rx produced decrease in level of pain activation in insula cortex. |
First study to Evaluate CNS effects on stimulus; this allowed for extraction of regions most affected by the Rx. |
| NaloxoneOpioid (μ antagonist) |
Borras et al., 2004. [59] |
10 subjects. Direct drug effects indicated increased in aCG, prefrontal cortex, hippocampus and entorrhinal cortex. Post infusion painful heat produced increase in activation (correlated with psychophysical effects). |
First study on opioids to address direct CNS effects. Naloxone is a drug that has no cognitive effects in normal healthy volunteers. |
| Morphine (μ agonist) |
Becerra 2006. [58] |
Low dose morphine produces changes in reward (SLEA, NAc, GOb) endogenous analgesia (PAG), and hypnotic circuits. |
fMRI of the effects of morphine on CNS circuits – indicating the use of this approach to define specific circuitry activated by a drug. |
| Antiseizure meds |
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| Gabapentin |
Ianetti et al., 2005 [41] |
Healthy volunteers. In a capsaicin model, single dose gabapentin has an antinociceptive effect but a stronger antihyperalgesic effect: the study indicates that the drug is more effective in the sensitized state. |
An excellent example of the application of fMRI to drug evaluation in dissecting the value of a model with potential clinical relevance. |
| Anti-inflammatory |
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| Cyclogoxygenase-2 inhibitor (Cox 2) |
Baliki et al., 2005 [61] |
Patient with psoriatic arthritis. Single subject evaluation. Activation induced by palpating joints included thalamus, insula, SI, SII, aCG. Rx produced decrease at 1 h. |
An example of specific application on evaluating efficacy of Rx. No drug site of action could be detected in this study. |
| Antidepressant |
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| Amitriptyline |
Morgan et al., 2005 [62] |
Evaluation of rectal pain in patients with irritable bowel syndrome. Rx produced a decrease in activation in aCG, parietal association cortex. |
Another example of how the focus on efficacy (CNS) of drugs may be evaluated. |
Borsook and Becerra Molecular Pain 2006 2:30 doi:10.1186/1744-8069-2-30 |
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