[Distribution of 14C-Diazepam (Valium) in pregnant and lactating rabbits]

14C-labelled Diazepam is applied i.v. in a single dose to pregnant rabbits and in three repeated doses to lactating rabbits. The distribution patterns of the radioactivity in the mother animal and in the fetus resp. in the sucklings are investigated at different intervals post inj. within a range of 10 to 120 minutes for the pregnant and at 8 hours after last injection for the lactating animals. With regard to its metabolic properties it is still admissible to identify the recorded radioactivity with the intact pharmaceutical to large extent for the intervals used in the experiments. The compound is distributed rapidly within the maternal organism and is excreted preferentially by the liver. Compared to blood level a considerable 14C-enrichment is obvious in the brain during the total time of investigation, which seem to be of special interest for the clinical use of the diazepam. An organotropism to the ovary is indicated by the patterns of radioactivity. A rapid diaplacental passage can also be shown, but the 14C-concentrations in blood and organ tissues of the fetus are generally found to be lower than those of the maternal organ tissues. Thus, the 14C-concentration in the fetal brain is equal to 1/3 of that of the maternal brain. Due to the mammoglandular passage the 14C-concentrations in the sucklings are reaching a maximum of one half of the values in the maternal organs.