External validation and updating of the infusion rate individualization of soybean oil-based intravenous lipid emulsion: A descriptive cohort study.

BACKGROUND: Safe and efficient provision of intravenous lipid emulsion (ILE) requires a strategy to individualize infusion rates. Estimating the maximum acceptable infusion rate (MaxInfRate) of soybean oil-based ILE (SO-ILE) in individuals by using a triglyceride (TG) kinetic model was reported to be feasible. In this study, we aimed to externally validate and, if needed, update the MaxInfRate estimation. METHODS: The maximum TG concentration (TGmax) in patients receiving SO-ILE at MaxInfRate was evaluated to determine if it met the definition of being <400 mg/dl for 90th percentile of patients. The TG kinetic model was evaluated through prediction performance checks and was subsequently updated using the data set of both the previous model development and present validation studies. RESULTS: Out of 83 patients, 74 had TGmax <400 mg/dl, corresponding to a probability of 89.2% (95% CI, 81.9%-95.2%), and the 90th percentile of TGmax was 400 mg/dl (95% CI, 328-490 mg/dl), closely aligned with the theoretical values. However, the individual TGmax values were biased by the infusion rate because the covariate effects were overestimated in the TG kinetic model, requiring a minor revision. The updated MaxInfRate with the combined data set showed unbiased and more accurate predictions. CONCLUSION: The MaxInfRate was validated in external inpatients and updated with all available data. MaxInfRate estimation for individuals could be an option for the safe and efficient provision of SO-ILE.

Model-Informed Vancomycin Dosing Optimization to Address Delayed Renal Maturation in Infants and Young Children with Critical Congenital Heart Disease.

Ensuring safe and effective drug therapy in infants and young children often requires accounting for growth and organ development; however, data on organ function maturation are scarce for special populations, such as infants with congenital diseases. Children with critical congenital heart disease (CCHD) often require multiple staged surgeries depending on their age and disease severity. Vancomycin (VCM) is used to treat postoperative infections; however, the standard pediatric dose (60-80 mg/kg/day) frequently results in overexposure in children with CCHD. In this study, we characterized the maturation of VCM clearance in pediatric patients with CCHD and determined the appropriate dosing regimen using population pharmacokinetic (PK) modeling and simulations. We analyzed 1,254 VCM serum concentrations from 152 postoperative patients (3 days-13 years old) for population PK analysis. The PK model was developed using a two-compartment model with allometrically scaled body weight, estimated glomerular filtration rate (eGFR), and postmenstrual age as covariates. The observed clearance in patients aged ≤ 1 year and 1-2 years was 33% and 40% lower compared with that of non-CCHD patients, respectively, indicating delayed renal maturation in patients with CCHD. Simulation analyses suggested VCM doses of 25 mg/kg/day (age ≤ 3 months, eGFR 40 mL/min/1.73 m2 ) and 35 mg/kg/day (3 months < age ≤ 3 years, eGFR 60 mL/min/1.73 m2 ). In conclusion, this study revealed delayed renal maturation in children with CCHD, could be due to cyanosis and low cardiac output. Model-informed simulations identified the lower VCM doses for children with CCHD compared with standard pediatric guidelines.

Real world population pharmacokinetic study in children and young adults with inflammatory bowel disease discovers novel blood and stool microbial predictors of vedolizumab clearance.

BACKGROUND: Vedolizumab for inflammatory bowel disease (IBD) is often intensified based on distinct pharmacokinetics in children. Prior adult-specific population pharmacokinetic models have identified limited covariates of drug clearance. AIMS: To establish a population pharmacokinetic model for children and young adults to identify novel covariates of drug clearance to better account for paediatric-specific inter-patient variability in vedolizumab pharmacokinetics; a key secondary exploratory aim was to identify microbial signatures of pharmacokinetic outcomes in a subset of patients. METHODS: The study included data from 463 observed vedolizumab concentrations (59 peaks and 404 troughs) from 74 patients with IBD (52 with Crohn's disease and 22 with ulcerative colitis or unclassified IBD, median age 16 years). Pharmacokinetic analysis was conducted with non-linear mixed effects modelling. For the evaluation of the exposure-response relationship, clinical outcomes were evaluated by trough levels, clearance and vedolizumab exposure. Whole-genome metagenomic sequencing was conducted at baseline and week 2. RESULTS: A two-compartment population pharmacokinetic model was identified with a clear correlation between CL and weight, erythrocyte sedimentation rate, and hypoalbuminemia. Trough concentrations before infusion 3 (37 µg/ml) and before infusion 4 (20 µg/ml) best predicted steroid-free clinical remission at infusion 4. Using faecal metagenomics, we identified an early (baseline and week 2) abundance of butyrate-producing species and pathways that were associated with an infusion 4 trough concentration >20 µg/ml. CONCLUSIONS: This novel paediatric vedolizumab pharmacokinetic model could inform precision dosing. While additional studies are needed, an abundance of faecal butyrate producers is associated with early response to vedolizumab, suggesting that microbial analysis may be beneficial to biological selection.

Comparison of cisplatin-induced nephrotoxicity between single-dose and split-dose administration to rats.

To prevent cisplatin (CDDP)-induced nephrotoxicity, co-treatment with massive hydration is essential for its clinical use. However, some patients are ineligible for this treatment. For such patients, a split dose of CDDP has been suggested as an alternative strategy. This study aimed to evaluate the nephrotoxicity of a split dose of CDDP by direct comparison with the conventional single dose of CDDP in rats. Rats were allocated to single- or split-dose groups. In the single-dose group, rats received the total dose of CDDP (from 0 to 7.5 mg/kg) with a single injection, whereas the same total dose of CDDP was split equally across five doses in the corresponding split-dose group. Blood samples were taken until day 21 after the first CDDP injection to monitor the plasma creatinine (Cr) concentration as an index of nephrotoxicity. CDDP-induced nephrotoxicities from day 1-10 and from day 15-21 were defined as acute kidney injury (AKI) and subchronic kidney injury (sCKI), respectively. The toxicity of CDDP-induced AKI in the split-dose group was found to be significantly lower than that in the single-dose group at any given total dose level. At a total dose of 7.5 mg/kg, a decrease of approximately 90% in AKI was found in the split-dose group, while the extent of attenuation of CDDP-induced sCKI in this group was approximately 30%. Our results provide evidence that a split-dose regimen could be an alternative strategy for CDDP-ineligible patients; however, the optimal regimen needs to be determined in future studies.

Individualization of the infusion rate of a soybean oil-based intravenous lipid emulsion for inpatients, based on baseline triglyceride concentrations: A population pharmacokinetic approach.

BACKGROUND: A rapid infusion rate for intravenous lipid emulsion (ILE) can cause adverse effects; therefore, safe and efficient infusion rates are desired. This study aimed to develop a triglyceride (TG) kinetic model after soybean oil-based ILE (SO-ILE) administration and individualize the infusion rate via a population pharmacokinetic approach. METHODS: Eighty-three inpatients were enrolled in this prospective observational study. A TG kinetic model was applied to the observations based on population pharmacokinetics using a nonlinear mixed-effect model. The patients' characteristics and laboratory parameters were evaluated to identify predictors of TG kinetics, and the maximum acceptable infusion rate was defined as that for which the maximum TG concentration did not exceed 400 mg/dl in 90% of patients. RESULTS: No adverse events associated with SO-ILE administration were observed. The developed TG kinetic model explained the observed TG concentrations and identified the baseline TG concentration and body weight as predictors of TG kinetics. The estimated maximum acceptable infusion rates greatly varied among individuals, ranging from <0.01 to 0.3 g/kg/h. CONCLUSION: The present study suggested the necessity and demonstrated the feasibility of individualizing the infusion rates of SO-ILE, using a population pharmacokinetic approach.

Population pharmacokinetics of tacrolimus in umbilical cord blood transplant patients focusing on the variation in red blood cell counts.

WHAT IS KNOWN AND OBJECTIVE: The distribution of tacrolimus (TAC), an immunosuppressant used during cord blood transplantation (CBT)-one of the haematopoietic stem cell transplantations, to red blood cell (RBC) is approximately 90% in whole blood. In CBT patients, the total RBC count shows dramatic fluctuation due to conditioning before transplantation, including anticancer agents and total body irradiation, as well as RBC transfusions during the treatment period. Therefore, the amount of TAC in whole blood may show wide variation. However, therapeutic drug monitoring (TDM) of TAC has been performed based on the whole blood concentration. In this study, to contribute to TDM of TAC in CBT, we performed the population pharmacokinetic (PPK) analysis of TAC in 56 CBT patients and investigated the factors that affected the concentration of TAC, focusing the variation of RBC count. METHOD: A one-compartment model was applied to the observed whole blood TAC concentrations, and a PPK analysis was conducted with a non-linear mixed effect model. RESULTS AND DISCUSSION: Our final PPK model indicated good robustness and accuracy. In addition, haemoglobin (Hb) level was an influential covariate on Vd, which was expressed as Vd(L) = 91.4 × (Hb/8.2)(-1.07) . WHAT IS NEW AND CONCLUSION: In this study, our results showed the necessity for the Hb level monitoring during TDM of TAC in CBT patients and provided useful information for improving TDM strategy of TAC.

Assessment of exposure risk of irinotecan and its active metabolite, SN-38, through perspiration during chemotherapy.

BACKGROUND: Irinotecan (CPT-11) is the key drug used in chemotherapy for many malignant tumors. CPT-11 has cholinergic activity and induces perspiration during intravenous administration. In this study, concentrations of CPT-11 and its active metabolite, SN-38, released during perspiration were measured and risk of exposure of these drugs was assessed. METHOD: Beads of sweat were collected using a dropper from four patients undergoing a chemotherapy regimen involving intravenous administration of CPT-11. The concentrations of CPT-11 and SN-38 in sweat were measured using liquid chromatography tandem mass spectrometry. RESULT: Chemotherapy regimens were capecitabine and irinotecan plus bevacizumab (n = 1), CPT-11 monotherapy (n = 1), and oxaliplatin-irinotecan-leucovorin-5-fluorouracil (n = 2). Uridine diphosphate-glucuronosyltransferase 1A1 phenotypes were *6 homo-type (n = 1), *6 hetero-type (n = 1), and wild type (n = 2). CPT-11 dose was 292.3 ± 75.5 mg/body weight (mean ± standard deviation). CPT-11 was detected in sweat secreted by all the four patients, and its mean (±standard deviation) concentration was 252.6 (±111.9) ng/ml. SN-38 was detected in only one of the patients who received oxaliplatin-irinotecan-leucovorin-5-fluorouracil treatment and who had the wild-type uridine diphosphate-glucuronosyltransferase 1A1 phenotype at a concentration of 74.37 ng/ml. CONCLUSION: CPT-11 and SN-38 are detected in sweat released during intravenous CPT-11 administration. Beads of sweat or linen clothes that absorb the sweat might be the source of CPT-11 and SN-38 exposure.

An LC-MS/MS Method for Absolute Quantification of Nivolumab in Human Plasma: Application to Clinical Therapeutic Drug Monitoring.

BACKGROUND: Nivolumab is a fully humanized IgG4 monoclonal antibody that targets the programmed death-1 (PD-1) receptor, disrupting PD-1-mediated signaling and restoring antitumor immunity. The objective of this study was to develop a nivolumab quantification method using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and to evaluate its application in clinical therapeutic drug monitoring. METHODS: Nivolumab was purified from human plasma using rProtein A resin and then digested with trypsin. The ASGITFSNSGMHWVR peptide (multiple reaction monitoring transition: m/z 550.6→661.4) was detected as a surrogate peptide of nivolumab by triple quadrupole mass spectrometry. Plasma samples (126) were collected from 14 patients with non-small cell lung cancer who were undergoing clinical dosing regimen with nivolumab. The pharmacokinetic data were analyzed using Phoenix NLME software (Version 7.0, Certara, St. Louis, MO) based on a previously reported population pharmacokinetics (PPK) model of nivolumab. RESULTS: Nivolumab was selectively detected in human plasma and the linear range was 5-200 mcg/mL (R = 0.99). The accuracy and intraday and interday imprecision were within ±15% of the quality control values of 5 (lower limit of quantification), 10 (low), 80 (medium), and 160 (high) mcg/mL. The nivolumab concentrations measured using LC-MS/MS were consistent with those of previously reported PPK models, and the pharmacokinetic parameters could be adequately predicted from a single trough concentration using a Bayesian approach. CONCLUSIONS: An absolute quantification method for nivolumab using LC-MS/MS was successfully developed and validated. Combined with PPK analysis, this method should be useful for the therapeutic drug monitoring of nivolumab in clinical practice.

Population Pharmacokinetics of Vancomycin in Patients Undergoing Allogeneic Hematopoietic Stem-Cell Transplantation.

Vancomycin is a commonly used antimicrobial agent for patients undergoing allogeneic hematopoietic stem-cell transplantation (allo-HSCT). Vancomycin has large inter- and intraindividual pharmacokinetic variability, which is mainly described by renal function; various studies have indicated that vancomycin pharmacokinetics are altered in special populations. However, little is known regarding vancomycin pharmacokinetics in patients undergoing allo-HSCT. Therefore, we aimed to develop a population pharmacokinetic (PopPK) model of vancomycin in patients undergoing allo-HSCT for effective and safe antimicrobial therapy and to develop a vancomycin dosing nomogram for a vancomycin optimal-dosing strategy. In total, 285 observations from 95 patients undergoing allo-HSCT were available. The final PopPK parameter estimates were central volume of distribution (V1, L), 39.2; clearance (L/h), 4.25; peripheral volume of distribution (V2, L), 56.1; and intercompartmental clearance (L/h), 1.95. The developed vancomycin model revealed an increase in V1 and V2 compared with those in the general population that consisted of patients with methicillin-resistant Staphylococcus aureus. Moreover, serum creatinine was reduced because of an increase in the plasma fraction because of destruction of hematopoietic stem cells accompanying allo-HSCT pretreatment, suggesting that the Cockcroft-Gault equation-based creatinine clearance value was overestimated. To our knowledge, this is the first PopPK study to develop a dosing nomogram for vancomycin in patients undergoing allo-HSCT and was proven to be useful in optimizing the dosage and dosing interval of vancomycin in these patients. This strategy will provide more useful information for vancomycin therapy with an evidence-based dose adjustment.

Pharmacokinetic-Pharmacodynamic Analysis of Cisplatin with Hydration and Mannitol Diuresis: The Contribution of Urine Cisplatin Concentration to Nephrotoxicity.

BACKGROUND AND OBJECTIVES: Forced diuresis, high-volume hydration with diuresis, is widely used as a prophylactic treatment against cisplatin nephrotoxicity. However, the details of the underlying mechanisms and the optimal protocol of forced diuresis remain unclear. The present study investigated the alterations in pharmacokinetics and pharmacodynamics (nephrotoxicity) of cisplatin with forced diuresis treatment. METHODS: Cisplatin (5 mg/kg) was intravenously injected to rats (5 rats/group, except for control group in pharmacodynamic study, n = 13) treated with or without forced diuresis 2-h pre- and post-hydration with 10% mannitol at different infusion rates (0.3, 1.0, and 3.0 mL/h). The unbound cisplatin concentrations in plasma and urine, and the platinum amount in the kidney were monitored in the pharmacokinetic studies. The plasma creatinine concentration was evaluated as an index of nephrotoxicity in the pharmacodynamic studies. RESULTS: Forced diuresis treatment did not significantly alter the plasma cisplatin pharmacokinetics but dramatically decreased the urine concentration of unbound cisplatin and its accumulation into the kidneys in a dose-dependent manner, and correspondingly, nephrotoxicity was dose-dependently attenuated by forced diuresis. The pharmacokinetic-pharmacodynamic analysis suggested that the urine cisplatin concentration has a comparable impact on the cisplatin-induced nephrotoxicity to that in plasma, probably owing to the reabsorption of cisplatin from urine, which can be attenuated by forced diuresis. CONCLUSIONS: These results indicated that the nephroprotective effect of forced diuresis is a pharmacokinetic-based drug-drug interaction possibly due to the inhibition of cisplatin reabsorption from urine. Monitoring of urine cisplatin concentration may lead to the optimization of a forced diuresis protocol with mannitol.

Alterations in Cisplatin Pharmacokinetics and Its Acute/Sub-chronic Kidney Injury over Multiple Cycles of Cisplatin Treatment in Rats.

Cisplatin (CDDP)-induced acute kidney injury (AKI) is a major clinical concern. CDDP treatment is generally conducted with multiple cycles; the magnitude of the CDDP-induced AKI may be altered by these cycles. Moreover, sub-chronic kidney injury (sCKI) induced by repeated CDDP treatment is often associated with renal interstitial fibrosis, potentially leading to chronic kidney disease. Therefore, it is suggested that the management of not only AKI but also sCKI induced by CDDP in multiple cycles plays an important role in the outcome of CDDP-based chemotherapy. This study investigated the alteration in pharmacokinetics and toxicodynamics of CDDP that was repeatedly administered for three cycles in rats; a cycle consisted of CDDP (5.0 mg/kg, bolus injection) followed by a 21-d washout period. AKI and sCKI were evaluated by plasma creatinine concentration. In repeated multiple administration of CDDP, renal clearance was decreased and the amounts of accumulated Pt in kidneys increased by the cycle. AKI and sCKI were similarly exacerbated by the cycle, whereas the degree of AKI showed a large inter- and intra-individual variation in each cycle. However, the degree of sCKI constantly increased (creatinine increasing ratio in any cycle is about 150%), suggesting that the degree of sCKI in any given cycle was predictable by monitoring the initial creatinine baseline. In this study, therefore, it is suggested that the evaluation of sCKI by monitoring creatinine concentration at base is important for the estimation of CDDP-induced nephrotoxicity. These results may provide useful information for more effective and safe CDDP-based chemotherapy with evidence-based dose adjustment.

Population pharmacokinetics of cyclosporine A in Japanese renal transplant patients: comprehensive analysis in a single center.

PURPOSE: Cyclosporine A (CyA), a potent immunosuppressive agent used in renal transplantation, has a narrow therapeutic window and a large variability in blood concentrations. This study aimed to develop a population pharmacokinetic (PPK) model of CyA in living-donor renal transplant patients at a single center and identify factors influencing CyA pharmacokinetics (PK). METHODS: A total of 660 points (preoperative) and 4785 points (postoperative) of blood concentration data from 98 patients who underwent renal transplantation were used. Pre- and postoperative CyA model structure and PPK parameters were separately estimated with a non-linear mixed-effect model, and subsequently, covariate analysis of postoperative data were comprehensively estimated, including preoperative PK parameters. RESULTS: A two-compartment model with first-order absorption and absorption lag time was selected in this study. Aspartate aminotransferase, body surface area (BSA), pretransplant area under the whole blood concentration-time curve/dose, and postoperative days were identified as the covariates on oral clearance. BSA was selected as a covariate of the distribution volume of the central compartment. In addition, diabetes mellitus was selected as a covariate of the first-order absorption rate. CONCLUSIONS: This PPK study used the largest number of blood concentration data among previous reports of living-donor renal transplant patients. Moreover, all patients received the same immunosuppressive regimen in a single center. Therefore, the validity of the selected covariates is reliable with high precision. The developed PPK model and selected covariates provide useful information about factors influencing CyA PK and greatly contributes to the identification of the most suitable dosing regimen for CyA.

Population Semiphysiologic Kinetic Modeling and Simulation of Plasma Triglyceride Levels After Soybean Oil-Based Intravenous Lipid Emulsion Administration in Rats.

BACKGROUND: Soybean oil-based intravenous lipid emulsion (SO-ILE) has clinical utility as an energy source and in lipid rescue therapy. However, an excessive infusion rate of SO-ILE in routine use and in lipid rescue therapy may cause serious side effects. There is little information about plasma triglyceride (TG) kinetics following SO-ILE administration. The present study aimed to develop a population semiphysiologic kinetic model of TG and to predict the TG kinetics even at extremely high concentrations in rats. MATERIALS AND METHODS: TG concentration profiles after intravenous bolus (0.1, 0.25, 0.5, 1.0, 1.5, and 2.0 g/kg) or infusion (3.0 g/kg/h for 1 hour) of SO-ILE to rats were analyzed by a kinetic model constructed with 4 pathways: apolipoprotein acquisitions, zero-order catabolism, first-order uptake to storage sites, and zero-order secretion from storage sites. The developed model was subjected to internal and external validation. RESULTS: Plasma TG concentrations appeared to decline in a biphasic manner with nonlinear TG kinetics. The developed kinetic model was well validated and found to accurately predict the external validation data. CONCLUSIONS: The proposed kinetic model accurately described TG concentrations after SO-ILE administration at various infusion rates, including a lipid rescue regimen. The maximum acceptable infusion rate of SO-ILE in routine use should correspond to the maximum velocity of the apolipoprotein acquisition: 0.619 g/kg/h in rats. The prediction of TG kinetics at extremely high concentrations will provide useful information for lipid rescue therapy.

Population Pharmacokinetic-Toxicodynamic Modeling and Simulation of Cisplatin-Induced Acute Renal Injury in Rats: Effect of Dosing Rate on Nephrotoxicity.

Nephrotoxicity is the major dose-limiting toxicity of cisplatin (CDDP). The aim of this study was to develop a pharmacokinetic (PK)/toxicodynamic (TD) model of CDDP-induced acute renal injury in rats and to simulate nephrotoxicity at various dosing rates. CDDP was administered to rats by a 30-s bolus or a 2-h infusion (1.0, 2.5, 5.0, and 7.5 mg/kg). Unbound CDDP concentrations in plasma and urine were determined up to 2 h after administration in the PK study, and plasma creatinine (Cr) levels were monitored for up to 7 days as an index of nephrotoxicity in the TD study. The PK was linear and was fitted with a traditional 2-compartment model. The TD was nonlinear and differed between dosing rates. The creatinine concentration profiles were fitted with a signal transduction-indirect response model. Population analysis using a nonlinear mixed-effect model was adapted to the developed PK/TD model and was well-validated. Dosing simulations from the developed population PK/TD model indicated that CDDP-induced nephrotoxicity was due to not only Cmax but also the time above the toxic concentration of CDDP. Prolongation of infusion time will not necessarily attenuate acute nephrotoxicity. This study demonstrated the potential utility of PK/TD modeling for preventing nephrotoxicity.

Enhanced oral bioavailability of vancomycin in rats treated with long-term parenteral nutrition.

Long-term parenteral nutrition (PN) can induce intestinal atrophy, leading to a loss of epithelial integrity in the small intestines. This change may alter the intestinal permeability of vancomycin (VCM), a non-absorbable antibiotic. The aim of the present study was to investigate the effect of PN on the pharmacokinetics of VCM in rats. VCM was intravenously (5 mg/kg) or intraduodenally (20 mg/kg) administered to control and PN rats, which were prepared by administration of PN for 9 days. After intravenous administration, there were no significant differences in any of the VCM pharmacokinetic parameters between the control and PN rats. However, after intraduodenal administration, the maximum concentration and area under the plasma concentration-time curve of VCM in PN rats was approximately 2.4- and 2.6-fold higher, respectively, than in the control rats; the calculated bioavailability was approximately 0.5 and 1.3 % in control and PN rats, respectively. These results indicated that PN administration did not affect VCM disposition, but enhanced VCM absorption; however, the enhanced oral VCM bioavailability was statistically, not clinically, significant. Therefore, while long-term PN administration may play a role in the enhancement of VCM bioavailability, this effect may be negligible without any complications.

Preparation of methacrylic acid copolymer S nano-fibers using a solvent-based electrospinning method and their application in pharmaceutical formulations.

In this study, we applied an electrospinning (ES) method, which is mainly employed in the textile industry, to the field of pharmaceuticals. We developed and modified an ES instrument and then utilized it to produce methacrylic acid copolymer S (MAC) nano-fibers to prepare tablets. By attaching a conductor rod made from stainless steel to the central part of the nano-fiber-collection plate of the ES apparatus, a MAC nano-fiber sheet could be produced effectively. In addition, we studied various operating conditions for this new ES method, including needle gauge, voltage between the electrodes, distance between the needle and nano-fiber-collection plate and the flow rate of MAC polymer solution, but these had no significant effect on the diameter of MAC nano-fibers. On the other hand, the viscosity (concentration) of MAC polymer solution and permittivity of solvent used to dilute MAC were closely related to the mean diameter of the nano-fibers. Tableting of MAC nano-fibers was performed using a tableting machine without lubricants, and addition of Tween 20 to the tablets enabled regulation of the release profile of a water-soluble drug. The modified ES method reported here is a useful technique for the controlled-release of drugs and has wide-ranging potential for pharmaceutical applications.

Effect of intestinal atrophy and hepatic impairment induced by parenteral nutrition on drug absorption and disposition in rats.

BACKGROUND: Long-term parenteral nutrition (PN) has a high risk of hepatic dysfunction and intestinal atrophy. The present study investigated the effect of PN-induced intestinal atrophy and hepatic impairment on drug pharmacokinetics by using 2 contrasting compounds: phenolsulfonphthalein (PSP) and cyclosporin A (CyA). MATERIALS AND METHODS: PSP or CyA was administered to 7-day PN-fed Rats (PN rats) and sham operated rats (control rats) via intravenous (IV) or intraloop administration of the intestine. Pharmacokinetic parameters with 2-compartment analysis including area under the concentration vs time curve (AUC) and the permeability after in situ intraloop administration (P loop) were obtained from both concentration profiles after different administration routes. RESULTS: After IV administration of PSP to control and PN rats, there was no notable difference in any of the pharmacokinetic parameters. In contrast, after intraloop administration, AUC and P loop in PN rats were approximately 2.6- and 2.0-fold higher than that in control rats, respectively. On the other hand, after IV administration of CyA, the terminal half-life and total body clearance were prolonged and decreased in PN rats, respectively, resulting in 2.0-fold increase in AUC. After intraloop administration, the AUC of PN rats was increased to approximately 1.3-fold that of control rats, whereas no notable difference was observed in P loop. CONCLUSION: The intestinal permeability of PSP was enhanced by intestinal atrophy induced by PN, while the metabolism of CyA was diminished by hepatic impairment by PN. These results revealed the physicochemical property-based pharmacokinetic alterations during PN; for a more detailed understanding, however, further studies are needed.

Preparation and pharmaceutical evaluation of nano-fiber matrix supported drug delivery system using the solvent-based electrospinning method.

In this study, utilizing the solvent-based electrospinning (ES) method, which is mainly employed in the textile industry, we prepared nanofiber-based capsules including drugs for controlled-release delivery systems using methacrylic acid copolymer (EUDRAGIT(®) S100, MAC) as a polymer, and evaluated their in vitro drug dissolution profiles and in vivo pharmacokinetics in rats. As the model drugs, uranine (UN) was used as a water-soluble drug and nifedipine (NP) as a water-insoluble drug. The mean diameters of drug free nano-fiber and nano-fiber including NP or UN were 751.5 ± 67.2, 703.3 ± 71.2 and 2477.8 ± 206.1 nm, respectively. X-ray diffraction for the nano-fibrotic sheet showed that UN and/or NP were packed in nano-fiber in an amorphous form. The in vitro release of UN or NP from the nano-fiber packed capsules (NFPC) and milled-powder of nano-fiber packed capsules (MPPC) showed controlled release of UN or NP as compared to capsules of a physical mixture of MAC and each drug. An in vivo pharmacokinetic study in rats after intraduodenal administration of NFPC or MPPC including UN and/or NP clearly demonstrated that application of nano-fibrotic technique as a drug delivery system offers drastic changes in pharmacokinetic profiles for both water-soluble and water-insoluble drugs. The ES method is a useful technique to prepare a nano-fiber like solid dispersion for polar or nonpolar drugs, and has wide potential pharmaceutical applications.

Dose adjustment strategy of cyclosporine A in renal transplant patients: evaluation of anthropometric parameters for dose adjustment and C0 vs. C2 monitoring in Japan, 2001-2010.

The optimal use and monitoring of cyclosporine A (CyA) have remained unclear and the current strategy of CyA treatment requires frequent dose adjustment following an empirical initial dosage adjusted for total body weight (TBW). The primary aim of this study was to evaluate age and anthropometric parameters as predictors for dose adjustment of CyA; and the secondary aim was to compare the usefulness of the concentration at predose (C0) and 2-hour postdose (C2) monitoring. An open-label, non-randomized, retrospective study was performed in 81 renal transplant patients in Japan during 2001-2010. The relationships between the area under the blood concentration-time curve (AUC0-9) of CyA and its C0 or C2 level were assessed with a linear regression analysis model. In addition to age, 7 anthropometric parameters were tested as predictors for AUC0-9 of CyA: TBW, height (HT), body mass index (BMI), body surface area (BSA), ideal body weight (IBW), lean body weight (LBW), and fat free mass (FFM). Correlations between AUC0-9 of CyA and these parameters were also analyzed with a linear regression model. The rank order of the correlation coefficient was C0 > C2 (C0; r=0.6273, C2; r=0.5562). The linear regression analyses between AUC0-9 of CyA and candidate parameters indicated their potential usefulness from the following rank order: IBW > FFM > HT > BSA > LBW > TBW > BMI > Age. In conclusion, after oral administration, C2 monitoring has a large variation and could be at high risk for overdosing. Therefore, after oral dosing of CyA, it was not considered to be a useful approach for single monitoring, but should rather be used with C0 monitoring. The regression analyses between AUC0-9 of CyA and anthropometric parameters indicated that IBW was potentially the superior predictor for dose adjustment of CyA in an empiric strategy using TBW (IBW; r=0.5181, TBW; r=0.3192); however, this finding seems to lack the pharmacokinetic rationale and thus warrants further basic and clinical investigations.

Effects of obesity induced by high-fat diet on the pharmacokinetics of atazanavir in rats.

We studied the effects of obesity on the pharmacokinetics of atazanavir (ATV) using a rat model of high-fat diet-induced obesity (obese rats). The areas under the plasma concentration-time curves for intravenous bolus, oral, and intraportal administration of ATV in obese rats were significantly greater than the corresponding values in control rats. Total plasma clearance of ATV after intravenous bolus injection in the obese rats (0.80 ± 0.07 L/h/kg) was approximately half of that in the control rats (1.55 ± 0.18 L/h/kg). Furthermore, ATV concentration in the plasma-unbound fraction of the obese rats (4.2% ± 2.6%) was significantly lower than that in the control rats (14.2% ± 2.3%). Such differences may result in changes in ATV distribution from the systemic circulation to peripheral or central tissues, and the pharmacological effects of ATV may therefore be reduced in obese patients. Moreover, hepatic extraction in the obese rats (13.5% ± 1.6%) was approximately 62% of that in the controls (21.9% ± 0.96%). These results suggest that hepatic metabolism decreased and that dosing regimens should be carefully evaluated in obese patients. Therefore, in obese patients, it is necessary to pay careful attention to therapeutic drug monitoring data, and the use of specific dosing regimens, as well as that of monitoring system for liver fat accumulation are recommended.