The pharmacokinetics of N-[14C-formyl]-leurosine in humans

N-Formyl-leurosine labeled with ¹⁴C in the formyl group was administered to six patients with malignant disease, and the pharmacokinetic behavior of the drug was determined. Chromatographic studies on plasma showed the presence of unchanged drug and 7 metabolites. No metabolites were found in the urine. The plasma decay curve of the unchanged drug was biphasic with half-life values of $\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2\alpha </mtext>}}\text{= 18.6 min}$ and $\text{t}{}_{\mathrm{<mtext>1</mtext><mtext>2\beta </mtext>}}\text{= 4.28 hr}$. Within 72 hr only 30–40% of the radioactivity could be recovered in urine and feces in 5 patients. One patient consumed laxatives during the treatment. In this case 95% of the ¹⁴C-dose was recovered. The contribution made by fecal elimination was 80%.