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Purpose: Clobazam (CLB) is metabolized by cytochrome P450 (CYP) 3A4 to yield N-desmethylclobazam ( N-CLB), which is further inactivated by CYP2C19. The aim of this study was to retrospectively evaluate the relationship between CYP2C19 polymorphisms and the efficacy of low-dose, add-on CLB therapy in Japanese patients with epilepsy. Methods: Fifty patients were divided into three groups according to their CYP2C19 polymorphism. CLB and N-CLB serum concentrations and seizure frequency before and after starting CLB were analyzed. Results: Extensive metabolizers (EMs, n = 11), intermediate metabolizers (IMs, n = 22), and poor metabolizers (PMs, n = 17) were included. Although the dose-normalized CLB serum concentrations were not significantly different, the dose-normalized N-CLB serum concentrations were significantly higher in PMs than in EMs or IMs. Seizure frequency was significantly decreased by the CLB therapy in PMs ( p < 0.01), but not in EMs or IMs. CLB serum concentrations did not correlate with seizure reduction rate, but median N-CLB serum concentrations were significantly higher in patients with excellent seizure control (≧90 % seizure reduction) compared to those with ≧50 % seizure reduction or with <50 % seizure reduction (1103, 341, and 570 ng/mL, respectively). Conclusions: The efficacy of low-dose CLB therapy was significantly influenced by CYP2C19 polymorphisms. Ideally, CLB therapy should be started with a low dose (2.5 mg/day) and dosage increased until N-CLB serum concentration reaches 1100 ng/mL or until the desired effect is acquired, a recommendation that is particularly important for PMs. [ABSTRACT FROM AUTHOR]

Purpose: Omeprazole has ( R)- and ( S)-enantiomers, which exhibit different pharmacokinetics (PK) among patients with cytochrome P450 (CYP) 2C19 genotype groups. The aim of this study was to investigate whether the 1-point, 4-h postdose ( R)-omeprazole hydroxylation index (HI) of racemic omeprazole reflects the three CYP2C19 genotype groups in Japanese individuals. Methods: Ninety healthy Japanese individuals were enrolled and classified into the three different CYP2C19 genotype groups: homozygous extensive metabolizers (hmEMs; n = 34), heterozygous EMs (htEMs; n = 44), and poor metabolizers (PMs; n = 12). Blood samples were drawn 4 h after the intake of an oral dose of omeprazole 40 mg, and plasma levels of omeprazole and its metabolites were analyzed by high-performance liquid chromatography (HPLC) using a chiral column. Results: Mean plasma concentrations of ( R)- and ( S)-omeprazole in PMs were significantly higher than those in hmEMs and htEMs, and similar results were obtained in the case of omeprazole sulfone. Additionally, there was a significant difference in plasma concentrations of ( R)-5-hydroxyomeprazole among CYP2C19 genotype groups, whereas no significant differences were observed in that of ( S)-5-hydroxyomeprazole. Similarly, ( R)-omeprazole HI in hmEMs, htEMs, and PMs were 5.6, 3.1, and 0.3, respectively, which were significantly different, but no significant difference was present in the ( S)-omeprazole HI. Conclusion: Our findings demonstrate that ( R)-omeprazole HI correlated better with CYP2C19 genotype groups than racemic-omeprazole HI, and these results may be useful for classification among patients in CYP2C19 genotype groups prior to omeprazole treatment. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to investigate the interactions of itraconazole (ITCZ) with orally administered calcineurin inhibitors (CNIs) in Japanese allogeneic hematopoietic stem cell transplant (HSCT) recipients. Methods: Sixteen HSCT patients (8 patients each receiving tacrolimus or cyclosporine) were enrolled. An ITCZ oral solution was administered from day 30 after the initiation of ITCZ administration as a loading dose. Before the co-administration of ITCZ and CNI and 1 week daily thereafter, whole blood ITCZ and CNI (tacrolimus or cyclosporine) concentrations were measured in samples taken just before (C) and 2 h (C) after CNI administration. Results: The median dose-adjusted C values of tacrolimus and cyclosporine on day 7 after the start of ITCZ co-administration were 5.6- and 2.7-fold higher, respectively, than the corresponding values obtained before the initiation of ITCZ treatment. On day 7 after ITCZ treatment, the mean single dosages of tacrolimus and cyclosporine were reduced to 33.7 and 66.5 % of the dosages before ITCZ co-administration, respectively, to adjust the CNI target concentration. Although ITCZ co-administration did not alter the dose-adjusted C values of tacrolimus in a patient with a CYP3A5*1/*1 allele, it did change this value of tacrolimus in patients with CYP3A5*3 alleles. However, in patients receiving cyclosporine, no such tendency was observed. Conclusion: The magnitude of the interaction between orally administered tacrolimus and ITCZ was significantly greater than that between cyclosporine and ITCZ. Prospective analysis of the CYP3A5 polymorphism may be important to ensure safe and reliable immunosuppressive therapy with tacrolimus in patients treated with ITCZ. [ABSTRACT FROM AUTHOR]

Objective: This study is a pharmacogenetic clinical trial designed to clarify whether the N-acetyltransferase 2 gene ( NAT2) genotype-guided dosing of isoniazid improves the tolerability and efficacy of the 6-month four-drug standard regimen for newly diagnosed pulmonary tuberculosis. Methods: In a multicenter, parallel, randomized, and controlled trial with a PROBE design, patients were assigned to either conventional standard treatment (STD-treatment: approx. 5 mg/kg of isoniazid for all) or NAT2 genotype-guided treatment (PGx-treatment: approx. 7.5 mg/kg for patients homozygous for NAT2*4: rapid acetylators; 5 mg/kg, patients heterozygous for NAT2*4: intermediate acetylators; 2.5 mg/kg, patients without NAT2*4: slow acetylators). The primary outcome included incidences of 1) isoniazid-related liver injury (INH-DILI) during the first 8 weeks of therapy, and 2) early treatment failure as indicated by a persistent positive culture or no improvement in chest radiographs at the8th week. Results: One hundred and seventy-two Japanese patients (slow acetylators, 9.3 %; rapid acetylators, 53.5 %) were enrolled in this trial. In the intention-to-treat (ITT) analysis, INH-DILI occurred in 78 % of the slow acetylators in the STD-treatment, while none of the slow acetylators in the PGx-treatment experienced either INH-DILI or early treatment failure. Among the rapid acetylators, early treatment failure was observed with a significantly lower incidence rate in the PGx-treatment than in the STD-treatment (15.0 % vs. 38 %). Thus, the NAT2 genotype-guided regimen resulted in much lower incidences of unfavorable events, INH-DILI or early treatment failure, than the conventional standard regimen. Conclusion: Our results clearly indicate a great potential of the NAT2 genotype-guided dosing stratification of isoniazid in chemotherapy for tuberculosis. [ABSTRACT FROM AUTHOR]

Purpose: Congestive heart failure (CHF) alters the pharmacokinetics of various drugs, including cardiovascular agents, due to decreased cardiac output and decreased renal blood flow. The purpose of this study was to evaluate the influence of CHF on the clearance of vancomycin, a glycopeptide antibacterial agent. Methods: After reviewing more than 1,500 clinical charts of patients who received vancomycin therapy and whose serum vancomycin level was monitored, we identified 101 patients who also had the left ventricular ejection fraction (LVEF) assessed at that time. The fluorescence polarization immunoassay method was used to measure vancomycin serum concentrations in these patients 1 h after the end of vancomycin infusion and just before the next administration. Using these two measurements, we calculated the pharmacokinetic parameters using the Bayesian estimator. Results: Patients with an LVEF of <40 % (16 patients) or those with an LVEF of ≥ 40 % and <60 % (40 % ≤ LVEF < 60 % ; 32 patients) had a significantly lower vancomycin clearance than patients with LVEF of ≥60 % (53 patients) (2.29 ± 0.95 or 2.79 ± 0.99 vs. 3.50 ± 1.04 L/h; p < 0.001 or p < 0.01, respectively). Vancomycin clearance was strongly correlated not only with estimated creatinine clearance (CLcr) in patients with an LVEF of <40 % ( r = 0.828) and 40 % ≤ LVEF < 60 % ( r = 0.773), but also with an LVEF in patients with a CLcr of <60 mL/min ( r = 0.646). Consistent with these findings, multiple regression analysis revealed that CLcr, LVEF and body weight were important independent variables for vancomycin clearance ( r = 0.649). Conclusions: Vancomycin clearance decreased with decreasing cardiac function (LVEF) and decreasing CLcr. This finding suggests that vancomycin clearance is affected by cardiac function and would be predicted not only CLcr but also by LVEF. [ABSTRACT FROM AUTHOR]