Metabolism of zimelidine in rat, dog and man. Identification and synthesis of the principal metabolites.

Several metabolites of (Z)-3-(4-bromophenyl)-N,N-dimethyl-3-(3-pyridyl)allylamine (zimelidine) were isolated from urine of rat and dog after administration of the 14C-labelled drug. The major metabolic routes found in these species involve oxidations at both the aliphatic and aromatic nitrogen, N-demethylations and deamination of the aliphatic nitrogen. The major excretion products in urine from both rat and dog were the N-oxide of zimelidine, the deamination product 3-(4-bromophenyl)-3-(3-pyridyl)-acrylic acid and its N-oxide. Apparently, there are only minor differences between rat and dog in the metabolism of zimelidine. The N-oxide of zimelidine and the acrylic acid derivative were also identified in a human urine sample. Zimelidine was labelled with 14C in the allylic position. Most of the metabolites were synthesized in pure diastereomeric form and their configuration were shown by UV and 1H-NMR.

On the mechanism of the accumulation of 3H-bretylium in peripheral sympathetic nerves.

The uptake of bretylium-(N-3H-methyl) iodide in the rat heart atrium in vitro was examined. The uptake was linear for at least 1 hr and was strongly inhibited by (+)-amphetamine, (-)-noradrenaline, desipramine, cocaine, DSP 4 [N-(2-bromobenzyl)-N-(2-chloroethyl)ethylamine hydrochloride], guanethidine and ouabain. The amphetamine sensitive part of the uptake was almost completely abolished by pre-treatment of the rats with 6-hydroxydopamine and was dependent on the presence of sodium ions. Reserpine had no effect. (+)-Amphetamine but not desipramine caused an increase of the efflux of bretylium from the tissue. The apparent Km value of the active bretylium uptake was 3 x 10(-6) M, which was 10 times higher than that of the uptake of (-)-noradrenaline in the rat heart atrium (Km = 3 x 10(-7) M). The inhibition constants (Ki) for bretylium in inhibiting the noradrenaline uptake and for (-)-noradrenaline in inhibiting the bretylium uptake were 7 x 10(-6) M and 4 x 10(-7) M, respectively. The results obtained support the hypothesis that bretylium is taken up by the same mechanism as that carrying noradrenaline into the nerve terminals but is not bound in the noradrenaline storage vesicles.