Metabolism of budralazine, a new antihypertensive agent, III

1. [14C]Budralazine (I) administered orally to normotensive and spontaneously hypertensive rats showed no significant difference in metabolic fate between the two groups. 2. Peak plasma levels of 14C were 3.6 microgram equiv. of I per ml in both normotensive and hypertensive rats. Approx. 5% of total 14C in the plasma consisted of I within 4 h, but thereafter the parent drug was not detected. Approx. 15% of 14C in the plasma consisted of 1-hydrazinophthalazine within 16 h after the administration. 3. 45% and 37% of the dose of 14C was excreted into urine and faeces within 24 h, respectively. 4. A high retention of 14C in the aorta wall was found and the time course of 14C in the aorta wall was compatible with that of the reduction in blood pressure. The radioactive materials retained in the aorta wall were likely to be I or 1-hydrazinophthalazine, probably the latter, following macroautoradiography in hypertensive rats.