Nahoko Kurosawa

Detection of the four sequence variations of MDR1 gene using TaqMan® MGB probe based real-time PCR and haplotype analysis in healthy Japanese subjects

OBJECTIVES P-glycoprotein (P-gp) is significant from the viewpoint of pharmacokinetics/pharmacodynamics (PK/PD). MDR1 gene encodes P-gp and has a wide variety of SNPs. As the SNPs may be one of the factors that induce pharmacogenetic individual difference, haplotype analysis is necessary to evaluate the PK/PD. DESIGN AND METHODS The SNPs of the detected MDR1 were -129T>C, 325G>A, 2677G>T/A, and 3435C>T. For the analysis of linkage disequilibrium (LD) and haplotype analysis, and for the reconstruction of the haplotype pair, ARLEQUIN and PHASE were employed. RESULTS The result of the chi(2) test detected significant LD between -129 and 2677, -129 and 3435, and 2677 and 3435. There were 9 haplotypes: T-G-C, T-T-C, C-T-C, T-A-C, C-A-C, T-G-T, T-T-T, C-G-T, and C-T-T. CONCLUSIONS LD was found among the positions -129, 2677 and 3435. As a result, 9 haplotypes exists in the Japanese population. These results suggest that it would be necessary to give consideration to haplotype for the purpose of evaluating the PK/PD of the drugs transported by P-gp.

Effects of diltiazem on plasma level and urinary excretion of digoxin in healthy subjects

To evaluate a possible effect of diltiazem hydrochloride (DTZ) on digoxin (DX) kinetics, we performed a study in which a single oral dose of DX (0.5 or 0.75 mg) was given with and without DTZ (30 mg three times daily for 1 wk) to six healthy subjects. DTZ increased plasma DX concentrations at 3, 4, 6, and 12 hr and decreased renal clearance of DX from 3.05 ± 0.126 to 2.31 ± 0.234 ml/min/kg. There was no significant change in absorption t½, peak concentration, peak concentration time, distribution t½, biologic elimination t½, or apparent volume of distribution with DTZ.

Determination of streptomycin in serum by high-performance liquid chromatography

A high-performance liquid chromatographic method was developed for monitoring the serum concentration of streptomycin. The method includes clean-up using a Sep-Pak C18 cartridge and quantitation using dihydrostreptomycin as an internal standard. Streptomycin and dihydrostreptomycin were separated by reversed-phase ion-pair chromatography on LiChrosorb RP-18 and detected by UV absorption (195 nm). The calibration graph of serum streptomycin concentration was linear over the range 5-50 micrograms/ml. Streptomycin was added to serum at the level of 20.0 micrograms/ml and its concentration was determined to be 18.9 micrograms/ml with a coefficient of variation of 2.07% (n = 5). The clinical application of this method was confirmed by comparison with fluorescence polarization immunoassay.

The Association Between Heterozygosity for UGT1A1*6, UGT1A1*28, and Variation in the Serum Total-Bilirubin Level in Healthy Young Japanese Adults

AIMS Considerable variations in the serum total-bilirubin concentrations are observed in healthy subjects. Both sex and the UGT1A1 homozygous genotypes,*6/*6 and *28/*28, are known to influence this variation. However, currently, there is no consensus on the relationship of the heterozygous genotypes *1/*6, *1/*28, or *6/*28 and interindividual variation in the serum total-bilirubin levels. In the present study, we sought to clarify the involvement of heterozygous alleles *6 and *28 in the interindividual difference in the serum total-bilirubin levels among healthy young Japanese adults. METHODS We enrolled 92 healthy Japanese aged 20-30 years (37 men and 55 women). The serum total-bilirubin levels were compared between men and women and with different UGT1A1 genotypes. Multiple regression analysis was used to investigate the relationships between individual differences in the serum total-bilirubin levels, UGT1A1 genetic variants, and sex. RESULTS Serum total-bilirubin levels were significantly lower in women than in men. There were also significant differences in the serum total-bilirubin levels between the *1/*1 and *1/*28 genotype, the *1/*1 and *6/*28 genotype, the *1/*6 and *1/*28 genotype, and also the *1/*6 and *6/*28 genotype. Multiple regression analysis showed significant relationships between the serum total-bilirubin level, the UGT1A1 genotypes *1/*28 and *6/*28, and sex. This model explained 42.3% of the interindividual variation in serum total-bilirubin levels. CONCLUSIONS We found that the UGT1A1 genotypes *1/*28 and *6/*28 as well as sex contributed to interindividual variations in the serum total-bilirubin levels. In contrast, UGT1A1*1/*6 showed only minimal involvement in individual differences in serum total-bilirubin levels.

Avoidance of hepatic first‐pass effect in the rabbit via rectal route of administration

To assess avoidance of hepatic first‐pass effect of drugs, we undertook in situ experiments using rectal administration of lidocaine in the rabbit. We also employed in situ duodenal route to estimate first‐pass metabolism across the gastrointestinal mucosa. Rabbits were administered lidocaine HCl intravenously (i.v., 50 mg/20 min) and portally (i.p.v., 33.3, 16.7, 8.3 mg/20 min) and avoidance of hepatic first‐pass effect (Fh) was calculated from the area under curve (AUC). Fh was about 30% and did not vary with increasing i.p.v. dose. Intravenous and i.p.v. administration was followed by duodenal (i.d.) or rectal (i.r.) administration and the absorption (fa), Fh, and avoidance of first‐pass effect in the duodenal mucosal membrane (Fm) were determined. With i.d. administration, lidocaine was absorbed completely with negligible first‐pass effect in the mucosa (Fm=1). On the other hand, while lidocaine was also absorbed almost completely via the i.r. route, avoidance of first‐pass effect was 60%, representing twice the bioavailability via i.d. administration. On the basis of these data, assuming that the first‐pass effect in the rectal mucosa was negligible, we estimate the fraction of rectal venous drainage bypassing the portal circulation and thus hepatic metabolism (fnh) to be about 40%. Copyright

Association between the low‑dose irinotecan regimen‑induced occurrence of grade 4 neutropenia and genetic variants of UGT1A1 in patients with gynecological cancers

The occurrence of severe neutropenia during treatment with irinotecan (CPT-11) is associated with the *6 and *28 alleles of uridine diphosphate glucuronosyltransferase 1A1 (UGT1A1). However, the correlation between these variants and the occurrence of severe neutropenia in a low-dose CPT-11 regimen for the treatment of gynecological cancers has not been extensively studied. There are also no studies regarding the association between the 421C>A mutation in ATP-binding cassette sub-family G member 2 (ABCG2) and the occurrence of severe neutropenia in CPT-11-treated patients with gynecological cancers. The present study was designed to determine the factors associated with the occurrence of grade 4 neutropenia during chemotherapy for gynecological cancers with combinations of CPT-11 and cisplatin or mitomycin C. In total, 44 patients with gynecological cancer were enrolled in the study. The association between the absolute neutrophil count (ANC) nadir values, the total dose of CPT-11 and the genotypes of UGT1A1 or ABCG2 was studied. No correlation was observed between the ANC nadir values and the total dose of CPT-11. The ANC nadir values in the UGT1A1*6/*28 and *6/*6 groups were significantly lower compared with those in the *1/*1 group (P<0.01). Univariate analysis showed no association between the occurrence of grade 4 neutropenia and the ABCG2 421C>A mutation. Subsequent to narrowing the factors by univariate analysis, multivariate logistic regression analysis only detected significant correlations between the occurrence of grade 4 neutropenia and the UGT1A1*6/*6 and *6/*28 groups (P=0.029; odds ratio, 6.90; 95% confidence interval, 1.22–38.99). No associations were detected between the occurrence of grade 4 neutropenia and the heterozygous variant (*1/*6 or *1/*28) genotype, type of regimen or age. In conclusion, the UGT1A1*6/*28 and *6/*6 genotypes were found to be associated with the occurrence of severe neutropenia in the low-dose CPT-11 regimen for gynecological cancers. This finding indicates that the determination of UGT1A1 variants may be as useful in CPT-11 chemotherapy for gynecological conditions as it is in colorectal and lung cancer patients treated with this drug.

[Absorption and first-pass-effect of salbutamol after intraduodenal and intrarectal administration in rabbits].

To understand the previous result of higher bioavailability of rectal salbutamol (SB) compared with oral SB, in situ experiments using rabbit duodenal and rectal loop were carried out. After the intravenous (i.v.) and intraportal (i.p.) dosing of SB, fraction of dose which avoids the hepatic first-pass-effect (Fh) was calculated from the areas under the blood concentration-time curve (AUC). The Fh was about 10% and unchanged significantly with increasing i.p. dose (5-20 mg). Intraduodenal (i.d.) or intrarectal (i.r.) dosing of SB was made after the i.v. and i.p. dosing, and the AUCs and the residual amount in the loop were obtained to estimate the parameters. The results of the i.d. and i.r. dosing were as follows; for the extent of bioavailability (EBA), 7.7 +/- 1.5% and 14.5 +/- 2.3%, for the fraction of dose absorbed (fa), 93.9 +/- 3.7% and 33.8 +/- 3.3%, and for the fraction of absorbed SB which avoids first-pass-effects (F), 8.4 +/- 1.9% and 43.0 +/- 6.0% (mean +/- S. E., n = 4). Consequently, SB dosed i.d. was absorbed completely, and received first-pass-metabolism in the mucosa (about 20%) and then in the liver (about 90%), which caused the low bioavailability. While, in i.r. dosing, SB absorption was poor. However, higher bioavailability was obtained owing to about 40% of rectal venous blood flow which bypasses the liver and negligible first-pass-metabolism in the mucosa (about 4%).