65 hours. The mean Vss was 20.1 L, and the CL was 598.3 mL/min. The active metabolite M3 showed a biphasic decline in concentration after reaching Cmax values (mean t½ 1.69 hours), whereas the decline of M4 appeared monophasic (mean t½ 0.52 hours). The concentrations of these metabolites were substantially lower than those of bendamustine. The concentrations of the dihydrolysis product HP2 were initially also much lower than the concentrations of bendamustine but, unlike the other analytes, small but measurable
levels of HP2 were still present at 24 hours after the start of the infusion, with a mean concentration at 24 hours selleckchem of 3.75 ng/mL. The TRA concentrations were characterized by a very slow decrease after reaching Cmax values. After 168 hours, the mean
TRA concentration was still 2.29 μg Eq/mL, and the mean t½ of the apparent terminal phase was estimated at 197 hours (Table 2). Bendamustine, M3, M4, and HP2 composed the bulk of the TRA early in the profile (almost 80%); however, their contribution to the TRA quickly declined to approximately 1% at 4 hours after the start of the infusion. Selleck FK506 The mean concentration ratio of TRA in plasma and in whole blood (Fig. 3) was ~1.4
immediately after the end of the infusion and approximately 1 at later time points. Fig. 3 Mean (±standard deviation) [n = 4–6] plasma to whole-blood concentration ratio of total radioactivity immediately after the end of a 60-minute (120 mg/m2, 80–95 μCi) 14C-bendamustine hydrochloride infusion and at Methamphetamine weekly time points thereafter. TRA total radioactivity 3.3 Excretion Balance For all six patients, urine and fecal samples were collected as planned during the first 168 hours after administration of 14C-bendamustine. Thereafter, urine and feces continued to be collected for longer periods in five and three patients, respectively, for up to 3 weeks. Figure 4 shows the mean cumulative urinary, fecal, and total recovery of TRA during 168 hours after 14C-bendamustine administration. At this point, approximately half (45.5%) of the administered radioactivity was recovered in urine and a quarter (25.2%) in feces, resulting in total recovery of 70.6% after 168 hours. After the extended collection period, the total recovery was increased to 76.0%. Individual excretion values are tabulated in Table 3. Fig.