Investigation of the boxed warnings in package inserts of prescription medicines for medical professionals in Japan

Objective: In the Japanese Pharmacists Act, article 25-2, revised in 2013, it states that pharmacists shall provide the necessary information and guidance to the patient based on pharmaceutical knowledge and experience for ensuring the proper use of the medicine dispensed. The package insert is one of the documents to be referred to when providing the information and guidance. The boxed warnings in package inserts that include the precautions and responses are the most significant parts, however, the suitability of boxed warnings for pharmaceutical practice has not been evaluated. The aim of this study was to investigate the boxed warning descriptions in package inserts of prescription medicines for medical professionals in Japan. Methods: Package inserts of prescription medicines listed in the Japanese National Health Insurance drug price list on March 1st 2015 were collected one by one by hand from the website of the Japanese Pharmaceuticals and Medical Devices Agency (https://www.pmda.go.jp/english/). Package inserts with boxed warnings were classified according to the Standard Commodity Classification Number of Japan based on the pharmacological activity of each medicine. They were also compiled according to their formulations. The boxed warnings were divided into the precautions and responses parts, and their characteristics were compared among medicines. (AU)

Stereoselective interaction of tolvaptan with amiodarone under racemic metabolic impact by CYP3A5 genotypes in heart failure patients.

PURPOSE: The diuretic effect of tolvaptan is largely blood level-dependent although it does exhibit interindividual differences according to cytochrome P450 (CYP) 3A5 genotype. This study aimed to investigate the pharmacokinetic relationship between plasma tolvaptan and its monohydroxylate enantiomers and the factors affecting their metabolism in heart failure patients. METHODS: Japanese heart failure patients (n = 88) receiving oral tolvaptan (median dosage 7.5 mg/day) were enrolled. Blood samples were collected prior to the dosing on day 6 or later after first administration to determine the plasma concentrations of tolvaptan and its monohydroxylate enantiomers. Gene polymorphisms of CYP3A5, carbonyl reductase (CBR) 1/3, and ATP-binding cassette subfamily B member (ABCB) 1 were analyzed for their impact on tolvaptan pharmacokinetics. Serum laboratory test values and concomitant use of amiodarone were evaluated as factors related to tolvaptan metabolism. RESULTS: The median of the sum of the 5S- and 5R-tolvaptan plasma concentrations was 48.9 (range, 15.3-100) ng/mL. CYP3A5 genotypes significantly affected the concentration ratio of all enantiomeric metabolites to tolvaptan, while the other metabolic-related gene polymorphisms had no influence. A negative correlation was found between serum albumin and the enantiomeric ratio of tolvaptan and monohydroxylate DM-4111. Concomitant use of amiodarone increased the plasma levels of whole tolvaptan but significantly decreased the metabolic ratios of 5R-tolvaptan. 5S-tolvaptan was selectively synthesized from ketone MOP-21826 by CBR1 with a substantially smaller reaction velocity compared to tolvaptan monohydroxylation by CYP3A4/5. CONCLUSION: This study clarified the racemic impact of CYP3A5 genotypes on tolvaptan metabolism. Amiodarone may stereoselectively interact with R-forms rather than S-forms of tolvaptan.

Investigation of the boxed warnings in package inserts of prescription medicines for medical professionals in Japan.

Objective: In the Japanese Pharmacists Act, article 25-2, revised in 2013, it states that pharmacists shall provide the necessary information and guidance to the patient based on pharmaceutical knowledge and experience for ensuring the proper use of the medicine dispensed. The package insert is one of the documents to be referred to when providing the information and guidance. The boxed warnings in package inserts that include the precautions and responses are the most significant parts, however, the suitability of boxed warnings for pharmaceutical practice has not been evaluated. The aim of this study was to investigate the boxed warning descriptions in package inserts of prescription medicines for medical professionals in Japan. Methods: Package inserts of prescription medicines listed in the Japanese National Health Insurance drug price list on March 1st 2015 were collected one by one by hand from the website of the Japanese Pharmaceuticals and Medical Devices Agency (https://www.pmda.go.jp/english/). Package inserts with boxed warnings were classified according to the Standard Commodity Classification Number of Japan based on the pharmacological activity of each medicine. They were also compiled according to their formulations. The boxed warnings were divided into the precautions and responses parts, and their characteristics were compared among medicines. Results: The number of package inserts found on the website of the Pharmaceuticals and Medical Devices Agency was 15,828. Boxed warnings were present in 8.1% of the package inserts. A description of adverse drug reactions accounted for 74% of all precautions. Most of the precautions were observed in the warning boxes of antineoplastic agents. Blood and lymphatic system disorders were the most common precaution. Responses in the boxed warnings directed toward medical doctors, pharmacists, and other healthcare professionals accounted for 100, 77, and 8% of all package inserts with a boxed warning, respectively. Explanations for patients were the second most frequent response. Conclusions: The majority of boxed warnings request therapeutic contribution by pharmacists, and the descriptions of these explanations and guidance by pharmacists to patients were found to be consistent with the Pharmacists Act.

Simultaneous determination of itraconazole and its CYP3A4-mediated metabolites including N-desalkyl itraconazole in human plasma using liquid chromatography-tandem mass spectrometry and its clinical application.

BACKGROUND: Itraconazole (ITZ), a triazole antifungal agent, is metabolized to hydroxy-ITZ (OH-ITZ), keto-ITZ (KT-ITZ), and N-desalkyl ITZ (ND-ITZ) by cytochrome P450 3A4. The pharmacokinetics of ND-ITZ remain largely unknown due to the lack of an accurate and reliable determination method. This study aimed to develop a simultaneous determination method for ITZ and its three major metabolites including ND-ITZ in human plasma using isocratic liquid chromatography coupled to tandem mass spectrometry and then apply the method in a clinical setting. METHODS: Plasma specimens were pretreated by protein precipitation with acetonitrile. The supernatant was separated on a 3-µm particle octadecyl silane column (75 × 2.0 mm I.D.) in an isocratic elution of acetonitrile and 5 mM ammonium acetate (pH 6.0) (57:43, v/v). The method was applied to 10 patients treated with oral ITZ. RESULTS: The calibration curves of ITZ, OH-ITZ, KT-ITZ, and ND-ITZ were linear over the concentration ranges of 15-1500, 15-1500, 1-100, and 1-100 ng/mL, respectively. The pretreatment recoveries and matrix factors were 90.1-102.2% and 99.1-102.7%. Their intra- and inter-assay accuracies and imprecisions were 94.1-106.7% and 0.3-4.4%. The plasma concentrations of ITZ, OH-ITZ, KT-ITZ, and ND-ITZ 12 h after dosing ranged from 32.5-1127.1, 19.0-1166.7, 1.1-5.4, and 3.5-28.3 ng/mL, respectively, in immunocompromised patients. CONCLUSIONS: This study developed a simultaneous determination method for concentrations of ITZ and its three metabolites including ND-ITZ in a clinical setting.

Impact of flavin-containing monooxygenase 3 and CYP2C19 genotypes on plasma disposition and adverse effects of voriconazole administered orally in immunocompromised patients.

Flavin-containing monooxygenase (FMO) 3 together with cytochrome P450 (CYP) 2C19 play a significant role in voriconazole N-oxidation. This study aimed to evaluate the influence of FMO3 and CYP2C19 genotypes on the plasma disposition and adverse effects of voriconazole in immunocompromised patients. Sixty-five Japanese immunocompromised patients receiving oral voriconazole were enrolled. Predose plasma concentrations of voriconazole and N-oxide were determined at day 5 or later. The adverse effects of voriconazole and the FMO3 and CYP2C19 genotypes were investigated. The patients with FMO3 E158K/E308G had a lower plasma concentration of voriconazole. The metabolic ratio to N-oxide was significantly higher in the FMO3 E158K/E308G group than in the wild group. In contrast, FMO3 V257M was not associated with the plasma concentration of voriconazole. No significant difference was observed in the saturation index, defined as a correlation coefficient of the regression line between the absolute plasma concentration of voriconazole and the inverse value of the metabolic ratio to N-oxide, between the FMO3 genotypes. CYP2C19 phenotype did not affect the plasma concentration and metabolic ratio of voriconazole. The saturation index of voriconazole rose in the order of CYP2C19 extensive, intermediate, and then poor metabolizer groups. However, the FMO3 and CYP2C19 genotypes and their associated voriconazole pharmacokinetics did not have an effect on the incidence of adverse effects. In conclusion, FMO3 E158K/E308G decreased the plasma concentration of voriconazole through its higher metabolic activity. The FMO3 genotype altered the plasma exposure of voriconazole, while the CYP2C19 phenotype affected the metabolic capacity in immunocompromised patients.

Mycophenolic acid exposure and complement fraction C3 influence inosine 5'-monophosphate dehydrogenase activity in systemic lupus erythematosus.

Background Mycophenolate mofetil has recently been reported to be effective against systemic lupus erythematosus. The influence of the pharmacokinetics of mycophenolic acid, the active form of mycophenolate mofetil and the major inactive mycophenolic acid phenolic glucuronide on the activity of the target enzyme inosine 5'-monophosphate dehydrogenase, is expected to be revealed. The aim of this study was to identify the factors associated with inosine 5'-monophosphate dehydrogenase activity in systemic lupus erythematosus patients. Methods Fifty systemic lupus erythematosus patients in remission maintenance phase (29 received mycophenolate mofetil [MMF+] and 21 did not [MMF-]) were enrolled. Median and interquartile range of dose of mycophenolate mofetil were 1500 and 1000-1500 mg/day, respectively. Stepwise multiple linear regression analysis was performed to assess the dependence between inosine 5'-monophosphate dehydrogenase activity and 25 predictor values including predose plasma concentrations of free mycophenolic acid and mycophenolic acid phenolic glucuronide. Results Median and interquartile range of predose total plasma concentrations of mycophenolic acid and mycophenolic acid phenolic glucuronide were 2.73 and 1.43-5.73 and 25.5 and 13.1-54.7 µg/mL, respectively. Predose inosine 5'-monophosphate dehydrogenase activity was significantly higher in MMF+ than MMF- patients (median 38.3 and 20.6 nmoL xanthosine 5'-monophosphate/g haemoglobin/h, P<0.01). The plasma concentration of free mycophenolic acid phenolic glucuronide, complement fraction C3 and body weight were significant predictors accounting for interindividual variability in the inosine 5'-monophosphate dehydrogenase activity (adjusted R2 = 0.52, P < 0.01) in a multivariate analysis. Conclusions Predose inosine 5'-monophosphate dehydrogenase activity was higher in systemic lupus erythematosus patients receiving mycophenolate mofetil therapy. Inosine 5'-monophosphate dehydrogenase activity may be determined by mycophenolic acid exposure and complement fraction C3 in systemic lupus erythematosus patients.

Validated determination method of tramadol and its desmethylates in human plasma using an isocratic LC-MS/MS and its clinical application to patients with cancer pain or non-cancer pain.

BACKGROUND: This study aimed to develop a simultaneous determination method for tramadol and its desmethylates in human plasma using isocratic liquid chromatography coupled to tandem mass spectrometry and to validate it for pharmacokinetic evaluation in patients with cancer pain or non-cancer pain. METHODS: The pretreatments for human plasma involved protein precipitation using acetonitrile and methanol under basic conditions. Tramadol, O-desmethylate, N-desmethylate, and N,O-didesmethylate were separated on an octadecylsilyl column filled with 3-µm particles using isocratic mixture of methanol and 0.15 % formic acid in water (35:65, v/v). The mass spectrometer was run in positive ion multiple reaction monitoring mode. This method was applied to the determination of plasma samples in patients treated with oral tramadol. RESULTS: The chromatographic total run time was 10 min. The calibration curves in human plasma of tramadol, O-desmethylate, N-desmethylate, and N,O-didesmethylate were linear over the concentration ranges of 12.5-1600, 2.5-320, 2.5-320, and 2.5-320 ng/mL, respectively. The lower limits of quantitation of tramadol and its desmethylates in human plasma were 12.5 and 2.5 ng/mL. Their extraction recoveries were 85.5-106.3 %. The intra-day and inter-day precisions and accuracies were 1.6-10.2 % and 89.2-106.2 % for all analytes. The plasma concentration ranges of tramadol, O-desmethylate, N-desmethylate, and N,O-didesmethylate were 18.2-564, 11.8-137, 4.9-250, and 6.1-147 ng/mL in cancer patients, and 32.8-670, 7.0-84.8, 5.1-317, and 6.7-85.2 ng/mL, respectively, in non-cancer patients. CONCLUSIONS: The present method with acceptable analytical performance can be helpful for evaluating the pharmacokinetics of oral tramadol, including the determination of its desmethylates, for patients with cancer pain or non-cancer pain in clinical settings.

[Optimization of Immunosuppression and the Prevention of Fungal Infection in Autoimmune Diseases].

Mycophenolate mofetil (MMF) has recently been reported to be effective in the treatment of systemic lupus erythematosus (SLE). The therapeutic range of mycophenolic acid (MPA) and its 7-O-glucuronide (MPAG), and factors affecting their pharmacokinetics, remain to be clarified. The influence of the pharmacokinetics of MPA and MPAG on the activity of inosine 5'-monophosphate dehydrogenase (IMPDH), a target of the MPA, also remains to be revealed. The pharmacokinetic variability of hydroxy-itraconazole (OH-ITZ), an active metabolite of itraconazole frequently co-administered with immunosuppressants in immunocompromised patients, is not fully known. The aim of this study was to establish the optimal dosage and administration of immunosuppressants and antifungal agents. MMF improved clinical laboratory markers and reduced prednisolone dosage in 31 SLE patients, with a pre-dose plasma concentration of MPA and MPAG in the interquartile ranges of 0.94-2.96 and 18.6-53.7 µg/mL, respectively. Renal function and co-administered metal influenced the pharmacokinetics of MPA and MPAG in 31 SLE patients in the remission maintenance phase. IMPDH activity was induced in 29 SLE patients receiving the MMF therapy. This induction was dependent on the plasma concentration of MPAG, but not MPA. In addition, IMPDH activity was negatively correlated with complement fraction C3. MPA exposure and disease activity in SLE patients may determine IMPDH activity. The pharmacokinetic variability of OH-ITZ was associated with saturated metabolism to keto-itraconazole, serum concentration of albumin, and renal function in 46 immunocompromised patients. Prevention of fungal infections and drug-drug interactions in immunocompromised patients can be obtained by considering these identified confounding factors.

Saturated Metabolism of Voriconazole N-Oxidation Resulting in Nonlinearity of Pharmacokinetics of Voriconazole at Clinical Doses.

Metabolic saturation of voriconazole based on the trough plasma concentrations of voriconazole and its major metabolite N-oxide were evaluated according to CYP2C19 genotypes in 58 Japanese patients receiving voriconazole (median dose; 200 mg twice daily) for prophylaxis or treatment. Predose trough plasma concentrations of voriconazole and N-oxide were monitored on day 5 d or later after initiation of voriconazole treatment. Large interindividual variations in trough plasma concentrations of voriconazole and N-oxide were observed. Dose-normalized trough plasma concentrations of voriconazole were strongly correlated with its absolute trough concentrations, and the straight regression line between them intersected close to the origin of the coordinates. No significant correlation was observed between the trough plasma concentrations of voriconazole and N-oxide. The inverse value of the metabolic ratio of N-oxide to voriconazole was strongly correlated with the absolute trough voriconazole concentrations. No significant differences in the trough plasma concentrations of voriconazole and N-oxide or the metabolic ratio of N-oxide to voriconazole between the CYP2C19 genotypes were observed. Saturated metabolism of voriconazole N-oxidation rather than CYP2C19 genotypes contributed to the nonlinear pharmacokinetics. The metabolic process converting voriconazole to N-oxide was saturated at the clinical dose.

ABCB1 genetic variant and its associated tacrolimus pharmacokinetics affect renal function in patients with rheumatoid arthritis.

BACKGROUND: This study aimed to evaluate the blood exposure of and clinical responses to tacrolimus based on genetic variants of CYP3A5 and ABCB1 in patients with rheumatoid arthritis. METHODS: Seventy rheumatoid arthritis patients treated with oral tacrolimus once daily were enrolled. Blood concentrations of tacrolimus and its major metabolite 13-O-demethylate at 12h after dosing were determined. The relationships between the tacrolimus pharmacokinetics and efficacy, renal function, and CYP3A5 and ABCB1 genotypes were evaluated. RESULTS: Dose-normalized blood concentration of tacrolimus was significantly higher in the CYP3A5*3/*3 group than in the *1 allele carrier group. A lower metabolic ratio of 13-O-demethylate to tacrolimus was observed in the CYP3A5*3/*3 group. The ABCB1 3435TT group had higher dose-normalized blood concentrations of tacrolimus and 13-O-demethylate. The blood tacrolimus concentration was inversely correlated with the estimated glomerular filtration rate (eGFR). ABCB1 C3435T but not CYP3A5 genotype had decreased eGFR. Patients lacking the CYP3A5*3 allele had a higher incidence of tacrolimus withdrawal. CONCLUSION: CYP3A5*3 increased the blood exposure of tacrolimus through its metabolic reduction. ABCB1 C3435T led to a higher blood exposure of tacrolimus and its major metabolite. The ABCB1 genetic variant and its associated tacrolimus pharmacokinetics affected renal function in rheumatoid arthritis patients.

Impact of inflammation and concomitant glucocorticoid administration on plasma concentration of triazole antifungals in immunocompromised patients.

BACKGROUND: The expression of hepatic CYP3A decreases with inflammatory response but increases with glucocorticoid administration. The aim of this study was to evaluate the plasma concentration of voriconazole and itraconazole under inflammatory conditions and glucocorticoid therapy. METHODS: Forty-one voriconazole- and 42 itraconazole-treated immunocompromised patients were enrolled in this study. Plasma concentrations of triazoles and their major metabolites at 12h after dosing were determined. The relationships between C-reactive protein (CRP), prednisolone dose, and plasma exposure parameters of triazole were evaluated. RESULTS: Plasma concentration of voriconazole was not correlated with that of its N-oxide. A higher CRP was correlated with a higher dose-normalized plasma concentration of voriconazole and a lower plasma concentration ratio of N-oxide to voriconazole. Prednisolone dose was weakly correlated with the plasma concentration ratio of N-oxide to voriconazole. Plasma concentration of itraconazole had a good correlation with that of its hydroxide. Parameters of itraconazole were not associated with CRP and prednisolone dose. CONCLUSIONS: An inflammatory state raised the plasma concentration of voriconazole through its metabolic reduction, while it did not have an effect on plasma concentration of itraconazole. Concomitant glucocorticoid administration slightly elevated the voriconazole metabolism, although it did not affect the plasma concentration of triazoles.

Blood distribution of bortezomib and its kinetics in multiple myeloma patients.

OBJECTIVES: Pharmacokinetic disposition of bortezomib in the blood has not been fully characterized in humans. This study aimed to evaluate the blood distribution of bortezomib and its kinetics in multiple myeloma patients. DESIGN AND METHOD: Eighteen multiple myeloma patients receiving bortezomib-dexamethasone combination therapy were enrolled. Blood specimens were drawn just before bortezomib administration on days 1 and 8 in the second and third cycles and after discontinuation. The relationships between bortezomib concentration and blood components were evaluated. RESULTS: Bortezomib concentration in the blood on day 1 was higher than that on day 8 in the second cycle. No difference was observed in bortezomib blood concentrations between day 8 in the second and third cycles. The bortezomib concentration in the blood and blood cells was 3- and 7-fold higher than that in plasma. Bortezomib concentration in the blood was correlated with the red blood cell count. The half-life of bortezomib in the blood was 23days. CONCLUSION: Bortezomib was taken up into red blood cells to only a limited extent and eliminated in parallel to the red blood cells' lifespan. The turnover of red blood cells can affect the pharmacokinetic disposition of bortezomib in multiple myeloma patients.

Interindividual variations in aprepitant plasma pharmacokinetics in cancer patients receiving cisplatin-based chemotherapy for the first time.

The pharmacokinetics of aprepitant, a neurokinin-1 receptor antagonist, have not been fully evaluated in clinical settings. The aim of this study was to characterize the plasma pharmacokinetics of aprepitant and reveal their influence of laboratory tests and cytochrome P450 (CYP) 3A5 gene polymorphisms in cancer patients. Forty-four Japanese cancer patients receiving cisplatin-based chemotherapy for the first time following oral aprepitant (125 mg on day 1 and 80 mg on days 2 and 3) were enrolled. The patients did not have gastrointestinal disease and the clinical laboratory values were within their normal reference levels. The plasma concentrations of aprepitant 24 (day 2 predose), 72, and 120 h after the first aprepitant administration were determined using LC-MS/MS. The relationships between plasma exposure to aprepitant and body weight, clinical laboratory values, age, gender, or CYP3A5*3 were investigated. The median and interquartile ranges of the 120-h area under the plasma concentration time curve (AUC)(0-120) of aprepitant were 73215 and 55518-91121 ng h/mL. The coefficient of variation value for aprepitant AUC(0-120) was 53%. The AUC(0-120) of aprepitant was correlated with the levels of total bilirubin and serum albumin, respectively (r=0.454, p<0.01 and r=0.287, p=0.06), but not with other non-genetic factors and CYP3A5 genetic variants in a univariate analysis. The AUC(0-120) of aprepitant was significantly correlated with the level of total bilirubin (adjusted R(2)=0.187, p<0.01) in a multivariate analysis. In conclusion, the plasma pharmacokinetics of aprepitant varied markedly in cancer patients receiving cisplatin-based chemotherapy for the first time and were correlated with the level of total bilirubin.

Hydroxy-itraconazole pharmacokinetics is similar to that of itraconazole in immunocompromised patients receiving oral solution of itraconazole.

BACKGROUND: The pharmacokinetic variability of hydroxy-itraconazole (OH-ITZ), an active metabolite of itraconazole (ITZ), is not fully known. METHODS: Oral solution of ITZ was administered in 46 immunocompromised patients as a single 200 mg dose for at least 12 days. The plasma concentrations of ITZ, active OH-ITZ, and keto-itraconazole (keto-ITZ), an inactive metabolite, 12 h after administration were determined by LC-UV or LC-MS/MS. RESULTS: The mean±SD of plasma concentrations of ITZ, OH-ITZ, and keto-ITZ were 833±468, 798±454, and 3.94±2.68 µg/l, respectively. A greater correlation coefficient was observed between plasma concentrations of ITZ and OH-ITZ (r=0.90, P<0.01) than between OH-ITZ and keto-ITZ (r=0.44, P<0.01). Plasma concentration of OH-ITZ was inversely correlated with concentration ratio of keto-ITZ to OH-ITZ (r=-0.52, P<0.01). Plasma concentrations of ITZ and OH-ITZ were correlated with serum concentration of albumin (r=0.36, P=0.01 and r=0.37, P=0.01) and estimated glomerular filtration rate (r=-0.27, P=0.08 and r=-0.35, P=0.02). CONCLUSIONS: The pharmacokinetic variability of OH-ITZ was associated with saturated metabolism to keto-ITZ, serum concentration of albumin, and renal function in immunocompromised patients. The plasma concentration of OH-ITZ was strongly correlated with that of ITZ. Prevention of fungal infections can be improved by determining the plasma concentration of ITZ or OH-ITZ.

Impact of CYP3A5 genetic polymorphism on cross-reactivity in tacrolimus chemiluminescent immunoassay in kidney transplant recipients.

BACKGROUND: Tacrolimus immunoassays possess cross-reactivity with metabolites in the blood. The aim of this study was to evaluate the cross-reactivity in tacrolimus chemiluminescent immunoassay (CLIA) in kidney transplant recipients and to characterize the cross-reactivity according to CYP3A5 genetic polymorphism. METHODS: The subjects were 50 kidney transplant recipients receiving low-dose tacrolimus. Blood levels of tacrolimus at 12h (C(12)) measured by CLIA were compared with that by LC-MS/MS using Bland-Altman analysis. The influence of CYP3A5 genotypes on the cross-reactivity in tacrolimus CLIA was evaluated by interaction plots. RESULTS: No significant difference was observed in tacrolimus C(12) between the CYP3A5*1/*3 and CYP3A5*3/*3 genotypes. The dose-normalized C(12) of tacrolimus was significantly higher in the CYP3A5*3/*3 genotype than in the CYP3A5*1/*3 genotype. The C(12) ratio of 13-O-demethylate to tacrolimus was significantly lower in the CYP3A5*3/*3 genotype than in the CYP3A5*1/*3 genotype. Tacrolimus C(12) measured by CLIA was 35% higher than that by LC-MS/MS. A higher cross-reactivity was observed in the patients with a tacrolimus C(12) of less than 3 µg/l and CYP3A5*1/*3 genotype. CONCLUSION: This study confirmed the cross-reactivity in CLIA in kidney transplant recipients receiving low-dose tacrolimus. High metabolic capacity associated with the CYP3A5*1 genotype affected the cross-reactivity in patients with low tacrolimus levels.

Impact of concomitant antacid administration on gabapentin plasma exposure and oral bioavailability in healthy adult subjects.

The aim of this open-label, randomized, and 3-period crossover study was to evaluate the influences of concomitant antacid administration on the plasma disposition, intestinal absorption, and urinary excretion of gabapentin in humans. Gabapentin (200 mg) was orally administered alone, with 1 g magnesium oxide (MgO), or with 20 mg omeprazole to 13 healthy adult subjects. Oral bioavailability (BA) of gabapentin was estimated by 24-h urine collection. The C(max), T(max) and AUC(0-∞) of gabapentin + MgO were significantly lower than that of gabapentin alone (by 33%, 36% and 43%, respectively) and gabapentin + omeprazole (by 29%, 46% and 40%, respectively). In contrast, no significant differences were observed in the plasma disposition parameters of gabapentin between the treatments with and without omeprazole. The gabapentin BA in the MgO treatment was significantly lower, by 32% and 39%, compared to the gabapentin alone and with omeprazole treatment, respectively. There was no significant difference in the gabapentin BA between the gabapentin alone and with omeprazole treatment. Concomitant MgO and omeprazole did not affect the renal clearance of gabapentin. In conclusion, concomitant MgO decreased the gabapentin exposure through the reduction of intestinal absorption extent and rate. This reduction may be independent of the suppression of gastrointestinal acidification caused by antacids.

Impact of CYP3A5 and ABCB1 gene polymorphisms on fentanyl pharmacokinetics and clinical responses in cancer patients undergoing conversion to a transdermal system.

The aim of this study was to evaluate the influence of CYP3A5 and ABCB1 gene polymorphisms on fentanyl pharmacokinetics and clinical responses in cancer patients undergoing conversion to a transdermal system. Sixty Japanese cancer patients being treated with a fentanyl transdermal reservoir system according to the current Japanese guidelines were enrolled. Blood samples were obtained 192 h after conversion to the fentanyl transdermal system. Clinical responses after fentanyl application were evaluated by determining the incidences of adverse effects and rescue medication. The plasma concentration of fentanyl normalized with the measured absorption rate was significantly higher in the CYP3A5*3/*3 group than in the *1/*1 and *1/*3 groups (p = 0.048 and 0.021, respectively). Greater incidences of central adverse effects were observed in CYP3A5*3/*3 patients than in *1/*1+*1/*3 patients (odds ratio [OR], 3.49; 95% confidence interval [95% CI], 1.13-10.75; p = 0.029). Fewer patients with the ABCB1 1236TT allele than the 1236C allele needed rescue medication (OR, 0.17; 95% CI, 0.03-0.89; p = 0.036). CYP3A5*3 affected the pharmacokinetics of fentanyl and increased the incidence of central adverse effects. ABCB1 1236TT was associated with decreased administration of rescue medication after switching to the transdermal fentanyl system. In conclusion, these gene polymorphisms may predict clinical responses to fentanyl in cancer patients being converted to the transdermal system.

Rapid simultaneous determination of voriconazole and its N-oxide in human plasma using an isocratic high-performance liquid chromatography method and its clinical application.

OBJECTIVES: The aim of this study was to develop a simultaneous determination method for voriconazole (VRCZ) and its N-oxide (VNO) in human plasma and to apply it to clinical samples. DESIGN AND METHODS: Plasma specimens were deproteinized with acetonitrile and then injected into an HPLC-UV system. VRCZ and VNO were separated on an ODS column filled with 2.3-µm particles using an isocratic mixture of acetonitrile/methanol/phosphate buffer 25/10/65 (v/v/v). Plasma concentrations of VRCZ and VNO in 25 patients were determined. RESULTS: Both VRCZ and VNO were linear (r>0.999) over the concentration ranges of 0.1-8.0mg/L. The run time for quantification of the analytes was 4 min. Interindividual variation in the plasma concentration of VRCZ that ranged from less than 0.1 to 6.96 mg/L was observed. VNO concentrations weakly depended on VRCZ dosage. CONCLUSIONS: The present method can contribute to the optimization of antifungal therapy using VRCZ.

Pharmacokinetic variability of mycophenolic acid and its glucuronide in systemic lupus erythematosus patients in remission maintenance phase.

The aim of this study was to identify factors affecting the pharmacokinetics of mycophenolic acid (MPA) and its 7-O-glucuronide (MPAG) in systemic lupus erythematosus (SLE) patients. Thirty-one SLE patients in remission maintenance phase treated with mycophenolate mofetil (median 1500 mg/d) and prednisolone and followed-up for up to 56 months (median 13 months) were enrolled. Creatinine clearance and metal medication were significant predictors accounting for interindividual variability in the dose-normalized predose plasma concentration (C0) of MPA (adjusted R²=0.305, p=0.01) in a multivariate analysis. Dose-normalized MPAG C0 was significantly correlated with only creatinine clearance (adjusted R²=0.135, p=0.03). The free fraction of MPA was significantly correlated with only serum albumin (adjusted R²=0.700, p<0.01). The free fraction of MPAG was significantly correlated with serum albumin, metal medication, and age (adjusted R²=0.598, p=0.02). In conclusion, renal function and co-administered metal influenced the pharmacokinetics of MPA and MPAG in SLE patients in remission maintenance phase.

Suitability of chemiluminescent enzyme immunoassay for the measurement of blood tacrolimus concentrations in rheumatoid arthritis.

OBJECTIVES: The aim of this study was to evaluate the suitability of chemiluminescent enzyme immunoassay (CLIA) for the monitoring of whole-blood tacrolimus concentrations in rheumatoid arthritis (RA) patients. DESIGN AND METHODS: Sixty-three RA patients and 47 renal transplant (RT) patients treated with tacrolimus were enrolled. Tacrolimus concentrations in spiked blood and patient blood were measured by CLIA and HPLC-MS/MS. The cross-reactivity in CLIA was evaluated using 13-O-demethylated or 31-O-demethylated tacrolimus. RESULTS: Tacrolimus concentrations measured by CLIA correlated with those measured by HPLC-MS/MS. Bland-Altman analysis revealed the 95% confidence intervals between CLIA and HPLC-MS/MS in RA and RT patients were -20.7 to 109.9% and -5.0 to 74.1%, respectively. While 31-O-demethylated tacrolimus cross-reaction amounted to an equivalent of 120% tacrolimus in CLIA, 13-O-demethylated tacrolimus did not cross-react. CONCLUSION: CLIA values should be carefully interpreted in RA patients, especially those receiving a low dose of tacrolimus.