The Metabolic Fate of the Coronary Dilator 4-(3,4,5-Trimethoxycinnamoyl)-1-(N-Isopropylcarbamoylmethyl)- Piperazine in the Rat,Dog and Man

1. An oral dose of the coronary dilator 4-(3,4,5-trimethoxycinnamoyl)-1- (N-isopropylcarbamoylmethyl)-piperazine was readily absorbed and more than 75% of the dose was excreted within 24 h by the rat, dog and man. In 4 days, rat, dog and man excreted in the urine and faeces respectively 32.5 and 62.3%, 43.9 and 49.1%, and 57.8 and 43.3%. Faecal radioactivity was mainly excreted via the bile.

2. Plasma concentrations of radioactivity reached a maximum within 1 h in rats and dogs and within 2 h in man. For several h, more than 50% of the radioactivity circulating in the plasma of rats and more than 80% in man was due to unchanged drug.

3. Sequential whole-body autoradiography of the rat indicated that much of the radioactivity was distributed in the liver, kidneys and gastrointestinal tract and that there was significant uptake into the heart and lungs.

4. Although similar metabolites were excreted by the rat, dog and man, the relative proportions differed. 11.7, 2.3 and 28.8% respectively of the unchanged drug were excreted in the urine and 13.1, 19.5 and 10.4% respectively of the principal metabolite a glucuronide whose exact structure was not determined. Other metabolites included 4-(3,4,5-trimethoxycinnamoyl)-1-carbamoylmethyl piperazine and N-(3,4,5-trimethoxycinnamoyl)-piperazine.