Introduction: Paracetamol is commonly used for its antipyretic properties and analgesic effects, but the central mechanism remains elusive. We designed a study in healthy volunteers to detect the central functional working mechanism of paracetamol. Subjects, material and methods: A total of 20 subjects had a baseline functional magnetic resonance imaging (fMRI) before the intake of 1000 mg paracetamol orally; 60 minutes later, a second fMRI was made aiming detection of regional blood flow differences. Results: A decreased connectivity was observed in the ventral volume of interest (VOI), with the posterior cingulate (with both the left anterior cingulate cortex (ACC) and right ACC: respectively, Ke = 576; t = −6.8894 and Ke = 185; t = −4.8178) and the inferior temporal left (Ke = 103; t = −5.0993); in the combined ventral and dorsal VOIs, the posterior cingulate (with the left ACC; Ke = 149; t = −4.5658) and, both with the right ACC, the inferior temporal left (Ke = 88; t = −3.8456) and the inferior frontal gyrus (Ke = 86; t = −4.3937) had a decrease in connectivity. An increase was seen in other regions, including, among others, the middle frontal and temporal gyri (respectively, Ke = 85; t = 4.4256 and Ke = 85; t = 5.6851), the inferior frontal (with the left ACC: Ke = 165; t = 4.4998) and the superior frontal gyrus (with the right ACC; Ke = 281; t = 4.5992), and the post/precentral gyrus (with the right ACC, respectively, Ke = 102; t = 6.0582 and Ke = 105; t = 4.0776). Conclusions: On fMRIs in healthy volunteers, the ingestion of paracetamol affects connections with the ACC. This suggests a central effect of paracetamol in cerebral areas known to be associated with pain. Further studies are needed to demonstrate the same effects in acute and chronic pain states.
The effects of reboxetine on emotional processing in healthy volunteers: an fMRI study
