Regional distribution of halopemide, a new psychotropic agent, in the rat brain at different time intervals and after chronic administration.

Only a very small amount of halopemide, a new psychotropic agent, structurally related to the butyrophenones, but with a different pharmacological and clinical profile, penetrates into the rat brain. The maximum concentration is reached between 1 and 2 hours after injection.Halopemide is evenly distributed over the brain, except for the septum and stria e medullares being regions of a higher concentration. The distribution profile does not change significantly up to 4 hours. The percentage of unaltered halopemide in the brain levels down gradually.After 8 hours only 0. 004% of the dose is present in the brain and hardly any profile is seen.In the pituitary gland however even after 8 hours labelled metabolites are not detectable, whereas the level of halopemide remains high. The concentration of halopemide in the adenohypophysis tends to be higher than in the neurohypofysis.The distribution profile, the brain concentration and the percentage of unaltered halopemide in the brain, pituitary gland and plasma are not significantly influenced by chronic treatment, indicating the absence of accumulation of halopemide.