Studies of excretion in rabbit milk after administration of carbon-14 labelled amitriptyline and nortriptyline.

The excretion with rabbit milk has been investigated after subcutaneous administration of carbon-14 labelled amitriptyline and nortriptyline. The amounts of drug material in suckling neonates from nursing rabbits dosed repeatedly with the two drugs were also measured. It was found that the concentrations of radioactivity in milk were of the same size as the concentration in serum. The concentrations of radioactivity in the organs of neonates, which had received milk from rabbits dosed for five days with either amitriptyline or nortriptyline were considerably below those found in the corresponding organs of the dam. Amitriptyline administration to the dams seems to lead to higher concentrations in the organs of the offspring than does nortriptyline administration.