Neuroleptic drugs in the human brain

Abstract

After discontinuation of neuroleptic agents, their effects are still present for a long time. The exact underlaying mechanisms are still unclear. In two previous studies we measured the concentrations and region-specific distribution of haloperidol (Kornhuber et al. 1999) and levomepromazine (Kornhuber et al. 2006) in postmortem human brain tissues. The aim of the present paper is to compare the results of these two studies. Even after short-term treatment, haloperidol and levomepromazine concentrations reach high levels in human brain tissue. Haloperidol concentrations in brain tissue are 10-30 times higher than the optimum serum concentrations in the treatment of schizophrenia. The brain-to-blood concentration ratio of levomepromazine is about 10. The estimated elimination half-life of these drugs in brain tissue are 6.8 days (haloperidol), 7.9 days (levomepromazine) and 27.8 days for the metabolite desmethyl-levomepromazine, respectively. After two half-lives (about 2 weeks), a considerable amount of drug remains in brain tissue. Haloperidol concentrations appeared to be homogeneously distributed across different brain areas, whereas levomepromazine shows a region-specific distribution, with highest values in the basal ganglia. The persistence of neuroleptic drugs in the human brain might explain their prolonged effects and side effects. The region-specific distribution of levomepromazine may increase our understanding of both the preferential toxicity of neuroleptic drugs against basal ganglia structures and higher basal ganglia volumes in patients treated with neuroleptics.