Comparative study of phenothiazine derivatives on monoamine metabolism--direct correlation between the concentrations of drugs and monoamine metabolites in the brain.

The pharmacokinetics (distribution and elimination) and pharmacodynamics (biochemical effects on monoamine systems) of phenothiazines including the novel compound, E-0663 (10-[3-(3-hydroxypyrrolidinyl)-propyl]-2-trifluoromethyl phenothiazine), in the central nervous system were investigated concurrently in mice using high-performance liquid chromatography with electrochemical detection. The elimination rate of E-0663 from the brain was longer than that of the classical compounds, chlorpromazine, perphenazine and triflupromazine. The phenothiazine (0.01-100 mumol/kg i.v.) increased the metabolites of catecholamines. Direct correlation analysis was applied to the intracerebral concentrations of the drugs and monoamine-related substances. Significant correlations were observed between the concentrations of drugs and dopamine metabolites (3,4-dihydroxyphenylacetic acid and homovanillic acid). The relative potency of the drugs for the effect on the extraneuronal process was promethazine less than chlorpromazine less than E-0663 less than triflupromazine less than perphenazine by covariance analysis. On the other hand, noradrenaline metabolite (3-methoxy-4-hydroxyphenylethylene glycol) also revealed a significant correlation, and the potency was highest in the case of E-0663. These results suggest that E-0663 possessed different pharmacokinetic profiles and a different spectrum in its action on monoamine metabolism from classical phenothiazines. The method described here is simple for comparing the real potency and is useful as a new approach in the biochemical pharmacology of centrally acting drugs.