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During cancer chemotherapy,myelosuppression is a frequently observed toxicity manifestation which may sometimes cause severe infections.In this regard,though leukopenia-induced infections are more closely related to neutrophil counts than leukocyte counts,it is important to evaluate both leukocyte counts and neutrophil counts as markers of myelosuppression.Neutrophil counts,however,are sometimes estimated to be half leukocyte counts without conducting differential leukocyte counts.In the present study,the authors evaluated the necessity of differential leukocyte counts during cancer chemotherapy using pooled laboratory data at the University of Fukui Hospital.Variation in the percentage of neutrophils in leukocytes was observed in each leukocyte range,with the neutrophil count decreasing in pace with decreases in the leukocyte count.As an alternative index to the neutrophil count,the utility of the leukocyte count is thus considered to be low in cancer chemotherapy.There was also a divergence between adverse event grade between neutrophil and leukocyte numbers.In addition,neutrophil counts in 14.8% of the patients (26)were less than 1000/μL in spite of the fact that their leukocyte counts were higher than 3000/μL,and it was noted that 23 of them had undergone a paclitaxel-containing regimen.These results suggested that leukocyte differential counts should be measured during cancer chemotherapy,especially during the nadir period and when receiving chemotherapy containing paclitaxel.

The enterohepatic recycling of a drug consists of its biliary excretion and intestinal reabsorption, which is sometimes accompanied by hepatic conjugation and intestinal deconjugation reactions. β-Glucuronidase, an intestinal bacteria-produced enzyme, can break the bond between a biliary excreted drug and glucuronic acid. Antibiotics such as ciprofloxacin can reduce the enterohepatic recycling of glucuronide-conjugated drugs. In this study, we established an in vitro system to evaluate the β-glucuronidase-mediated deconjugation of the irinotecan metabolite SN-38-G to its active SN-38 form and the effect of ciprofloxacin thereon. SN-38 formation increased in a time-dependent manner from 5 to 30 min. in the presence of β-glucuronidase. Ciprofloxacin and phenolphthalein-β-D-glucuronide (PhePG), a typical β-glucuronidase substrate, significantly decreased SN-38-G deconjugation and, hence SN-38 formation. Similarly, the antibiotics enoxacin and gatifloxacin significantly inhibited the conversion of SN-38-G to SN-38, which was not observed for levofloxacin, streptomycin, ampicillin and amoxicillin/clavulanate. Ciprofloxacin showed a dose-dependent inhibitory effect on the β-glucuronidase-mediated conversion of SN-38-G to SN-38 with a half-maximal inhibitory concentration (IC50 ) value of 83.8 μM. PhePG and ciprofloxacin afforded the inhibition in a competitive and non-competitive manner, respectively. These findings suggest that the reduction in the serum SN-38 concentration following co-administration of ciprofloxacin during irinotecan treatment is due, at least partly, to the decreased enterohepatic circulation of SN-38 through the non-competitive inhibition of intestinal β-glucuronidase-mediated SN-38-G deconjugation.

Cyclosporin A pharmacokinetics was studied in rats with cisplatin-induced acute renal failure (ARF) using microemulsion preconcentrate (MEPC) and completely dissolved formulations. Although the pharmacokinetics of cyclosporin A was unchanged after intravenous administration, maximum concentration of cyclosporin A in ARF rats was significantly reduced to 608+/-62 and 999+/-189 ng/ml compared with 1720+/-142 and 1832+/-250 ng/ml in controls after oral administration of MEPC and completely dissolved formulations, respectively. In an in situ intestinal loop sac study, the amount absorbed plus metabolized and the blood concentration of cyclosporin A were similar between control and ARF rats, and taurocholic acid, one of the bile acids, significantly increased absorption of cyclosporin A using the MEPC formulation in both control and ARF rats; the amount absorbed plus metabolized with taurocholic acid was increased to 137 and 186%, and simultaneously the blood concentration was increased to 155 and 158% of that without taurocholic acid in control and ARF rats, respectively. The bile flow in ARF rats was decreased compared with that in controls. These results suggested that renal dysfunction decreased the absorption of cyclosporin A in spite of the MEPC formulation, and the alternation of bile secretion partly affected the absorption rate of cyclosporin A in the gastrointestinal tract.

Organosilicon polymers have attracted considerable attention as a new class of functional polymers of the next generation because of their unique electronic and optical properties originating from the delocalization of σ-σ * conjugated electrons along the Si-Si main chain of polysilane. Thus, for these polymers, oxygen is the most remarkable impurity. Nevertheless, the determination of oxygen in any organic material is extremely difficult. Especially, for oraganosilicon compounds, conventional methods do not give good results. In this study we investigated the reason for the low recoveries of organosilicon compounds by several kinds of determination methods, and developed a new determination method involving on inert-gas fusion equipped converter, which includes platinum-carbon. According to our method, oxygen in organosilicon polymers can be determined quantitatively. We confirmed that our new method is applicable not only to organosilicon materials, but also to organic and organometallic compounds as well as inorganic materials.