Quantitative EEG and psychometric analyses in assessing CNS-activity of Ro 13-5057--a cerebral insufficiency improver

In a double-blind, placebo-controlled cross-over study, the encephalotropic, psychotropic and pharmacodynamic properties of Ro 13-5057/001, a new 2-pyrrolidinone derivative, were investigated in 10 geriatric subjects. They received in randomized order at weekly intervals, single oral doses of placebo, 250 mg, 500 mg and 1000 mg Ro 13-5057, as well as 2000 mg pirazetam as reference drug. EEG recordings, psychometric testing and evaluation of blood pressure, pulse rate and side effects were carried out at the hours 0, 2, 4, 6, 8 and 24. Power spectral density analysis of the EEG demonstrated Ro 13-5057 to be an encephalotropic drug, as statistically significant CNS changes occurred in comparison to placebo, which were characterized by a decrease of delta activity, increase of alpha activity and slow beta activity and acceleration of dominant frequency. The reference drug 2000 mg pirazetam induced similar changes. Such alterations were previously described by us as typical for certain antihypoxidotic/nootropic drugs and are indicative of improvement in vigilance. Psychometric data confirmed this interpretation of neurophysiological alterations as shortening of reaction time, acceleration of tapping speed, CNS activation as measured by the Archimedean spiral, improvement in mood as well as improvement in qualitative but deterioration of quantitative aspects of attention were observed at various times after the active substances as compared with placebo. Regarding time-efficacy, the peak effect in CNS changes was noted in the 2nd hour after Ro 13-5057, but interestingly there were also alterations as late as 24 hours after oral administration. Dose-efficacy curves suggested 1000 mg Ro 13-5057 as the most effective compound of the study. The lack of side effects and clinically relevant changes in blood pressure and pulse rate indicates that the drug is well tolerated in man.