Evaluation of encephalotropic and psychotropic properties of gabapentin in man by pharmaco-EEG and psychometry.

In a double-blind, placebo-controlled study the encephalotropic and psychotropic properties of gabapentin - a new gaba-analogue with anticonvulsant and antispastic properties penetrating the blood brain barrier easily - were studied in 10 normal subjects by means of quantitative pharmaco-EEG and psychometric analyses. They received randomized and in weekly intervals single oral doses of 50 mg, 100 mg, 200 mg and 400 mg gabapentin as well as placebo. EEG recordings and evaluation of pulse, blood pressure and side effects were carried out after 0, 1, 2, 4, 6 and 8 hours; psychometric tests were done at the same times except for the first hour. Computer-assisted spectral analysis of the EEG showed moderate though significant central effects of gabapentine in doses of 200-400 mg as compared with placebo, which were maximally pronounced in the 2nd hour post drug. These alterations were generally characterized by an attenuation of total power, augmentation of delta and theta activity and a decrease of alpha activity indicating CNS-inhibitory properties. Only at the late hours did the type of changes shift towards a vigilance-promoting one. Beta activity showed alternating changes. Psychometric and psychophysiological evaluations demonstrated subtle psychotropic effects as compared with placebo characterized mostly by an improvement in concentration, numerical memory, complex reaction and performance in the alphabetical reaction test while performance variability increased as well. Subjectively experienced well-being changed dose-dependently. CFF decreased after 100 mg as did pupil size after 50-200 mg. Evaluation of pulse, blood pressure and side effects demonstrated good tolerability of the drug.