Further absorption studies with the anti-diarrhoeal agent ethacridine lactate in the dog.

2-Ethoxy-6,9-diaminoacridine lactate (ethacridine lactate, Rivanol, Metifex) has been administered orally to the dog once daily for 14 days, tritium labelled matterial having been given on days 1 and 14. The extent and rates of urinary excretion of radioactivity and the peak plasma levels and total radioactivity half-lives following the radiolabelled doses on days 1 and 14 were essentially the same. There was no significant change following multiple dosing in the level of urinary acridine-like material as determined fluorimetrically, which compared to approximately 0.01% of the dose found in the 0--24 h urine. It was concluded that, following oral administration of 3H-ethacridine lactate (5 mg/kg), less than 0.1% of the dose is absorbed as acridine-like material. Multiple dosing for 14 days does not alter this very low degree of oral absorption. In a separate study tritiated ethacridine lactate (30 microgram/kg) was administered i.v. to the dog. Approximately 84% of the radioactivity was eliminated in the 0--72 h post dose period, the majority of it being excreted via the faeces. There was a rapid loss of radioactivity from the plasma, followed by a long terminal phase in which acridine-like material was estimated to have a half-life of about 15 h.