Pentazocine and Flupirtine Effects on Spontaneous and Evoked EEG Activity

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Abstract
Somatosensory (SEP), auditory evoked potentials (AEP) and power spectral density of ongoing EEG (PSD) were investigated under different drug conditions: the opioid pentazocine (30 mg), the centrally acting non-narcotic analgesic flupirtine (80 mg) and placebo were administered i.v. in a double-blind cross-over study (intersession interval 7 days) with 20 healthy male subjects. Intracutaneous electrical stimuli were applied to the finger tip with randomized intensities of two- and threefold individual pain threshold. One stimulus block consisted of 80 trials. Mean values of two stimulus blocks per session were analyzed: one block before and one block 30 min after treatment. Pentazocine significantly reduced the peak- to peak amplitude of the late SEP components (N150-P240) from pretreatment to postreatment blocks, and flupirtine diminished this amplitude to nearly the same degree. With placebo no substantial reduction was found. In contrast to these drug-induced changes in SEP, the AEP components showed no significant alterations after any treatment. The PSD under pentazocine showed a reduction of total power. This effect was mainly due to a reduced power in the alpha band. The PSD under flupirtine showed slight increases in power of theta, alpha and beta activity. Again, under placebo no changes from pretreatment to post-treatment conditions occurred. The difference in EEG change might suggest different sites of action of the two analgesics.