Cassia angustifolia and tacrolimus interaction in a liver transplant patient, a case report.

Cassia angustifolia is a species of plant from the Senna family that has traditionally been used as a laxative in different herbal products and commercial medicines. Even though there are few documented drug-plant interactions, the use of C. angustifolia with different drugs may have additive effects, such as with other laxatives or potassium-depleting diuretics. Its use also increases peristalsis which, may reduce drug absorption. The combination with digoxin has been associated with an increased risk of digoxin toxicity, probably due to an increase in plasma digoxin concentrations and hypokalaemia. We present a case with supratherapeutic trough concentration of tacrolimus, an immunosuppressive agent, and a herbal product in a liver transplant patient after concomitant intake of tacrolimus and a herbal product based on C. angustifolia, suggesting a possible drug-lant interaction through by P-glycoprotein. We observed an increase in the patient's blood concentration 2.8-fold and the area under the curve at steady state 2.1-fold. This interaction could be of clinical relevance, given the dose-dependent side effects of tacrolimus, such as nephrotoxicity, neurotoxicity, hypertension, hyperglycaemia, or electrolyte alterations.

Population Pharmacokinetic Model of Adalimumab Based on Prior Information Using Real World Data.

Adalimumab is a fully human monoclonal antibody used for the treatment of inflammatory bowel disease (IBD). Due to its considerably variable pharmacokinetics and the risk of developing antibodies against adalimumab, it is highly recommended to use a model-informed precision dosing approach. The aim of this study is to develop a population pharmacokinetic (PopPK) model of adalimumab for patients with IBD based on a literature model (reference model) to be used in the clinical setting. A retrospective observational study with 54 IBD patients was used to develop two different PopPK models based on the reference model. One of the developed models estimated the pharmacokinetic population parameters (estimated model), and the other model incorporated informative priors (prior model). The models were evaluated with bias and imprecision. Clinical impact was also assessed, evaluating the differences in dose interventions. The developed models included the albumin as a continuous covariate on apparent clearance. The prior model was superior to the estimated model in terms of bias, imprecision and clinical impact on the target population. In conclusion, the prior model adequately characterized adalimumab PK in the studied population and was better than the reference model in terms of predictive performance and clinical impact.

Cost-Effectiveness of Therapeutic Drug Monitoring of Anti-TNF Therapy in Inflammatory Bowel Disease: A Systematic Review.

Infliximab and adalimumab are monoclonal antibodies against tumor necrosis factor (anti-TNF) used to manage inflammatory bowel disease (IBD). Therapeutic Drug Monitoring (TDM) has been proven to prevent immunogenicity, to achieve better long-term clinical results and to save costs in IBD treatment. The aim of this study was to conduct a systematic review on cost-effectiveness analyses of studies that apply TDM of anti-TNF in IBD and to provide a critical analysis of the best scientific knowledge available in the literature. The quality of the included studies was assessed using Consolidated Health Economic Evaluation Reporting Standards (CHEERS). Cost-effectiveness of the TDM strategies was presented as total costs, cost savings, quality-adjusted life-years (QALY) and incremental cost-effectiveness ratio (ICER). Thirteen studies that examined the health economics of TDM of anti-TNF in IBD from 2013 to 2021 were included. Eight of them (61.5%) achieved a score between 17 and 23 on the CHEERS checklist. The comparison between the TDM strategy and an empirical strategy was cost saving. The ICER between reactive TDM and an empirical strategy was dominated (favorable) by reactive TDM, whereas the ICER value for proactive TDM compared to an empirical strategy ranged from EUR 56,845 to 3,901,554. This systematic review demonstrated that a TDM strategy is cost-effective or cost-saving in IBD.

Development of a Population Pharmacokinetic Model of Busulfan in Children and Evaluation of Different Sampling Schedules for Precision Dosing.

We develop a population pharmacokinetic model to describe Busulfan pharmacokinetics in paediatric patients and investigate by simulations the impact of various sampling schedules on the calculation of AUC. Seventy-six children had 2 h infusions every 6 h. A two-compartment linear model was found to adequately describe the data. A lag-time was introduced to account for the delay of the administration of the drug through the infusion pump. The mean values of clearance, central volume of distribution, intercompartmental clearance, and peripheral volume of distribution were 10.7 L/h, 39.5 L, 4.68 L/h and 17.5 L, respectively, normalized for a Body Weight (BW) of 70 kg. BW was found to explain a portion of variability with an allometric relationship and fixed exponents of 0.75 on clearance parameters and 1 on volumes. Interindividual variability for clearance and volume of distribution was found to be 28% and 41%, respectively, and interoccasion variability for clearance was found to be 11%. Three sampling schedules were assessed by simulations for bias and imprecision to calculate AUC by a non-compartmental and a model-based method. The latter was found to be superior in all cases, while the non-compartmental was unbiased only in sampling up to 12 h corresponding to a once-daily dosing regimen.

Evaluation of the Predictive Performance of Population Pharmacokinetic Models of Adalimumab in Patients with Inflammatory Bowel Disease.

Adalimumab is a monoclonal antibody used for inflammatory bowel disease. Due to its considerably variable pharmacokinetics, the loss of response and the development of anti-antibodies, it is highly recommended to use a model-informed precision dosing approach. The aim of this study is to evaluate the predictive performance of different population-pharmacokinetic models of adalimumab for inflammatory bowel disease to determine the pharmacokinetic model(s) that best suit our population to use in the clinical routine. A retrospective observational study with 134 patients was conducted at the General University Hospital of Alicante between 2014 and 2019. Model adequacy of each model was evaluated by the distribution of the individual pharmacokinetic parameters and the NPDE plots whereas predictive performance was assessed by calculating bias and precision. Moreover, stochastic simulations were performed to optimize the maintenance doses in the clinical protocols, to reach the target of 8 mg/L in at least 75% of the population. Two population-pharmacokinetic models were selected out of the six found in the literature which performed better in terms of adequacy and predictive performance. The stochastic simulations suggested the benefits of increasing the maintenance dose in protocol to reach the 8 mg/L target.

Population pharmacokinetics models of sirolimus in renal transplant patients: A systematic review.

OBJECTIVE: Sirolimus is used in the immunosuppressive therapeutic treatment  of kidney transplant patients. The high pharmacokinetic variability of sirolimus  makes pharmacokinetic monitoring and dosage individualization of  mmunosuppressive therapy a key process to achieve better efficacy results.  The availability of a population pharmacokinetic model can be used to provide  better pharmacokinetic adjustment of plasma concentrations of sirolimus and  thus achieve greater clinical benefit. METHOD: We conducted a systematic review of the literature available in the  Medline, Embase, and Scopus databases to identify and subsequently analyze  population pharmacokinetic models of orally administered sirolimus in adult  patients after kidney transplant. The descriptors used MeSH were kidney  transplantation, pharmacokinetics, and sirolimus. The following variables from  the selected studies were assessed: study population, immunosuppressive  treatment, blood sampling times, covariates analyzed, type of pharmacokinetic  model, computer software used, estimated pharmacokinetic  parameters, interindividual variability of pharmacokinetic parameters, residual  variability and mathematical equations of the pharmacokinetic model. RESULTS: A total of 548 results were obtained, excluding 175 records that were  identified in more than one database. Finally, seven articles that  et  the inclusion criteria were selected. Most of the pharmacokinetic models found fit a two-compartment model. The interindividual variability of sirolimus  was explained by covariates such as age, weight, liver function, cyclosporine exposure and dose, sirolimus doses, CYP3A5 genetic  olymorphisms, serum creatinine, and concomitant treatment. CONCLUSIONS: The two-compartment model was the pharmacokinetic model of  choice in most of the selected studies. The interindividual variability of the  pharmacokinetic parameters of sirolimus is explained by demographic, clinical,  genetic, and biochemical variables. The availability of pharmacokinetic models  of sirolimus can assist in optimizing therapy in patients after kidney transplant.

OBJETIVO: Sirólimus es un fármaco utilizado en los esquemas terapéuticos inmunosupresores en pacientes con trasplante renal. La elevada  variabilidad farmacocinética de sirólimus hace que la monitorización  farmacocinética y la individualización posológica de la terapia inmunosupresora sea un proceso crucial para conseguir mejores resultados de  eficacia. La disponibilidad de un modelo farmacocinético poblacional permite  realizar un mejor ajuste farmacocinético de las concentraciones plasmáticas de  sirólimus y así conseguir un mayor beneficio clínico.Método: Se realizó un análisis sistemático de la literatura disponible en las  bases de datos Medline, Embase y Scopus para identificar y posteriormente analizar los modelos farmacocinéticos poblacionales de  irólimus administrado por vía oral en pacientes adultos con trasplante renal. Se utilizaron como descriptores MeSH: kidney transplantation, pharmacokinetic  y sirolimus. De cada artículo seleccionado se evaluó: la  población a estudio, el esquema de tratamiento inmunosupresor, los tiempos  de muestreo de las extracciones de sangre, las covariables analizadas, el tipo  de modelo farmacocinético, el programa informático utilizado, los parámetros  armacocinéticos estimados, la variabilidad interindividual de  los parámetros  farmacocinéticos, la variabilidad residual y las ecuaciones matemáticas del  modelo farmacocinético. RESULTADOS: Se obtuvieron un total de 548 resultados, excluyendo 175  registros tras identificarse en más de una base de datos. Finalmente se  seleccionaron siete artículos que cumplían los criterios de inclusión. La mayoría  de los modelos farmacocinéticos encontrados siguen un modelo  bicompartimental. Covariables como edad, peso, función hepática, exposición y  dosis de ciclosporina, dosis de sirólimus, polimorfismos genéticos del  CYP3A5, creatinina sérica y tratamiento concomitante explican la variabilidad  interindividual de sirólimus. CONCLUSIONES: El modelo bicompartimental fue el modelo farmacocinético de  elección en la mayoría de los estudios seleccionados. La variabilidad interindividual de los parámetros farmacocinéticos de sirólimus se explica por variables demográficas, clínicas, genéticas y bioquímicas. La disponibilidad de modelos farmacocinéticos de sirólimus permiten  ndividualizar la terapia en pacientes con trasplante renal.

Modelos farmacocinéticos poblacionales de sirólimus en pacientes trasplantados renales: Revisión sistemática / Population pharmacokinetics models of sirolimus in renal transplant patients: A systematic review

Objetivo: Sirólimus es un fármaco utilizado en los esquemas terapéuticos inmunosupresores en pacientes con trasplante renal. La elevada variabilidad farmacocinética de sirólimus hace que la monitorización farmacocinética y la individualización posológica de la terapia inmunosupresorasea un proceso crucial para conseguir mejores resultados de eficacia. Ladisponibilidad de un modelo farmacocinético poblacional permite realizar un mejor ajuste farmacocinético de las concentraciones plasmáticasde sirólimus y así conseguir un mayor beneficio clínico.Método: Se realizó un análisis sistemático de la literatura disponible enlas bases de datos Medline, Embase y Scopus para identificar y posteriormente analizar los modelos farmacocinéticos poblacionales de sirólimusadministrado por vía oral en pacientes adultos con trasplante renal. Seutilizaron como descriptores MeSH: kidney transplantation, pharmacokinetic y sirolimus. De cada artículo seleccionado se evaluó: la poblacióna estudio, el esquema de tratamiento inmunosupresor, los tiempos demuestreo de las extracciones de sangre, las covariables analizadas, eltipo de modelo farmacocinético, el programa informático utilizado, losparámetros farmacocinéticos estimados, la variabilidad interindividual de los parámetros farmacocinéticos, la variabilidad residual y las ecuacionesmatemáticas del modelo farmacocinético.Resultados: Se obtuvieron un total de 548 resultados, excluyendo175 registros tras identificarse en más de una base de datos. Finalmentese seleccionaron siete artículos que cumplían los criterios de inclusión.La mayoría de los modelos farmacocinéticos encontrados siguen unmodelo bicompartimental. Covariables como edad, peso, función hepática, exposición y dosis de ciclosporina, dosis de sirólimus, polimorfismosgenéticos del CYP3A5, creatinina sérica y tratamiento concomitante explican la variabilidad interindividual de sirólimus. (AU)

Objective: Sirolimus is used in the immunosuppressive therapeutictreatment of kidney transplant patients. The high pharmacokinetic variability of sirolimus makes pharmacokinetic monitoring and dosage individualization of immunosuppressive therapy a key process to achieve betterefficacy results. The availability of a population pharmacokinetic modelcan be used to provide better pharmacokinetic adjustment of plasma concentrations of sirolimus and thus achieve greater clinical benefit.Method: We conducted a systematic review of the literature availablein the Medline, Embase, and Scopus databases to identify and subsequently analyze population pharmacokinetic models of orally administered sirolimus in adult patients after kidney transplant. The descriptorsused MeSH were kidney transplantation, pharmacokinetics, and sirolimus.The following variables from the selected studies were assessed: studypopulation, immunosuppressive treatment, blood sampling times, covariates analyzed, type of pharmacokinetic model, computer software used,estimated pharmacokinetic parameters, interindividual variability of pharmacokinetic parameters, residual variability and mathematical equationsof the pharmacokinetic model. Results: A total of 548 results were obtained, excluding 175 records thatwere identified in more than one database. Finally, seven articles that met theinclusion criteria were selected. Most of the pharmacokinetic models foundfit a two-compartment model. The interindividual variability of sirolimus wasexplained by covariates such as age, weight, liver function, cyclosporineexposure and dose, sirolimus doses, CYP3A5 genetic polymorphisms, serumcreatinine, and concomitant treatment. (AU)

Envarsus, una novedad para los nefrólogos del trasplante: estudio observacional retrospectivo / Envarsus, a novelty for transplant nephrologists: Observational retrospective study

El objetivo del presente estudio fue evaluar las concentraciones valle (Cpvalle) y la pauta posológica de tacrolimus tras la conversión de Prograf o Advagraf a Envarsus (nueva forma farmacéutica con tecnología Meltdose que mejora la absorción de fármacos liposolubles) en pacientes con trasplante renal estable, y su función renal. Se seleccionaron los pacientes trasplantados renales estables que fueron convertidos a Envarsus. Se definieron dos periodos: basal y conversión (Envarsus), y se estratificaron en función de la forma farmacéutica utilizada en el periodo basal. Se incluyeron 61 pacientes (24 con Advagraf y 37 con Prograf), con una edad media de 52 años. El tiempo medio postrasplante en el momento de la conversión a Envarsus fue de 76,3 meses y el seguimiento medio en el periodo basal y conversión fue de 10,1 y 11,6 meses, respectivamente. En el grupo Prograf y Envarsus las medianas Cpvalle fueron 6,6 vs 6,4 ng/ml (p = 0,636), con una dosis diaria media que disminuyó significativamente de 3 a 2 mg (p < 0,001), respectivamente, manteniendo el filtrado renal. Las medianas Cpvalle en los grupos Advagraf y Envarsus fueron 5,7 y 6,3 ng/ml (p = 0,07), con una mediana de dosis diaria de 7 y 4 mg (p < 0,001), respectivamente, e igual función renal. En pacientes trasplantados renales estables la conversión de Advagraf a Envarsus ha permitido reducir la dosis de tacrolimus un 42,9% y la de Prograf un 33,3% para mantener unas Cpvalle similares, sin que se altere la función renal

The aim of this study was to evaluate the trough concentrations (Cptrough) and the tacrolimus dosage regimen after the conversion of Prograf or Advagraf to Envarsus (new pharmaceutical form with MeltDose technology that improves the absorption of fat-soluble drugs) in patients with stable renal transplantation, and their renal function. We selected stable renal transplant patients who were converted to Envarsus. Two periods were defined: Baseline and Conversion (Envarsus) and they were stratified according to the pharmaceutical form used in the Baseline period. Sixty-one patients were included (24 with Advagraf and 37 with Prograf), with an average age of 52 years. The mean post-transplant time at the time of conversion to Envarsus was 76.3 months and the mean follow-up in the Baseline and Conversion period was 10.1 months and 11.6 months, respectively. In the Prograf and Envarsus group, the Cptrough medians were 6.6 vs 6.4 ng/mL (P = .636), with a mean daily dose that decreased significantly from 3 mg to 2 mg (P < .001), respectively, maintaining the filtration rate. The median Cptrough values in the Advagraf and Envarsus groups were 5.7 ng/mL and 6.3 ng/mL (P=.07), with a median daily dose of 7 mg and 4 mg (P<.001), respectively, and the same renal function. In stable renal transplant patients, the conversion from Advagraf to Envarsus has allowed the dose of tacrolimus to be reduced by 42.9% and, in the case of Prograf, by 33.3%, maintaining similar Cptrough values, without renal function being altered

Optimization of a paediatric fixed dose combination mini-tablet and dosing regimen for the first line treatment of tuberculosis.

We aim to optimize the paediatric dosing regimen of isoniazid, rifampicin and pyrazinamide for the first-line treatment of tuberculosis, based on a fixed dose combination (FDC) mini-tablet using simulations. An optimization problem was set up to determine the 3 strengths of the drugs of the mini-tablet and 4 cutoff points that define the weight bands of a dosing chart, simultaneously. Using Monte Carlo simulations, first, exposure targets were determined for the 3 drugs, from published population pharmacokinetic models for adults, assuming that the approved doses for adults are de facto efficacious. Then optimal strengths and cutoff points were determined by matching children exposures generated from population pharmacokinetic models to the adults targets. The optimal dosing strengths of the FDC tablet were found to be 95 mg of rifampicin, 200 mg of pyrazinamide and 75 mg of isoniazid, and the 4 body weight bands for 1 to 4 mini-tablets, respectively were: 4 to 8 kg, 8 to 12 kg, 12 to 18 kg and 18 to 28 kg. Children with body weight ≥ 28 kg will be treated with adult dosages. The higher doses proposed were evaluated to be much closer to the adult targets compared to the existing recommended by WHO paediatric doses.

Envarsus, a novelty for transplant nephrologists: Observational retrospective study. / Envarsus, una novedad para los nefrólogos del trasplante: estudio observacional retrospectivo.

The aim of this study was to evaluate the trough concentrations (Cptrough) and the tacrolimus dosage regimen after the conversion of Prograf or Advagraf to Envarsus (new pharmaceutical form with MeltDose technology that improves the absorption of fat-soluble drugs) in patients with stable renal transplantation, and their renal function. We selected stable renal transplant patients who were converted to Envarsus. Two periods were defined: Baseline and Conversion (Envarsus) and they were stratified according to the pharmaceutical form used in the Baseline period. Sixty-one patients were included (24 with Advagraf and 37 with Prograf), with an average age of 52years. The mean post-transplant time at the time of conversion to Envarsus was 76.3months and the mean follow-up in the Baseline and Conversion period was 10.1months and 11.6months, respectively. In the Prograf and Envarsus group, the Cptrough medians were 6.6 vs 6.4 ng/mL (P=.636), with a mean daily dose that decreased significantly from 3mg to 2mg (P<.001), respectively, maintaining the filtration rate. The median Cptrough values in the Advagraf and Envarsus groups were 5.7ng/mL and 6.3ng/mL (P=.07), with a median daily dose of 7mg and 4mg (P<.001), respectively, and the same renal function. In stable renal transplant patients, the conversion from Advagraf to Envarsus has allowed the dose of tacrolimus to be reduced by 42.9% and, in the case of Prograf, by 33.3%, maintaining similar Cptrough values, without renal function being altered.

Suitability of the AUC Ratio as an Indicator of the Pharmacokinetic Advantage in HIPEC.

The purpose of this study was to evaluate the area under the concentration-time curve (AUC) ratio as an optimal indicator of the pharmacokinetic advantage during hyperthermic intraperitoneal perioperative chemotherapy. The impact on the AUC ratio on the variables related to the calculation of systemic drug exposure, instillation time, and peripheral drug distribution was evaluated through simulations as well as through a retrospective analysis of studies published in the literature. Both model simulations and the retrospective analysis showed that the 3 variables evaluated had an impact on the AUC ratio value if the complete systemic exposure was not fully considered. However, when that complete systemic exposure was considered, none of these variables affected the AUC ratio value. AUC ratio is not a characteristic parameter of a drug if the calculated systemic drug exposure is not complete. Thus, AUC ratio is not valid for comparing the pharmacokinetic advantage of 2 drugs, and it should not be employed to prove whether a drug can be used in hyperthermic intraperitoneal perioperative chemotherapy safely with regard to toxicity. As an alternative, the study of the absorption rate constant and the bioavailability are proposed as the true and independent parameters that reflect the amount of drug absorbed.

Impact of Laparotomy and Intraperitoneal Hyperthermic Instillation (LIHI) on the oxaliplatin pharmacokinetics after intravenous administration in Wistar rats.

PURPOSE: In peritoneal metastasis condition, the fact that most of the disease is limited to the peritoneal cavity laid the foundations for a surgical treatment, including intraperitoneal hyperthermic chemotherapy (HIPEC). The aim of this study was to evaluate the impact of the surgical procedures implied in open HIPEC technique, referred to laparotomy procedures followed by an intraperitoneal hyperthermic instillation (LIHI) on oxaliplatin tissue distribution and elimination. To delimit the influence of this procedure alone, oxaliplatin was administered as an intravenous (iv) bolus in both groups. METHODS: An experimental model in Wistar rats was employed, and LIHI was evaluated as a dichotomous covariate by using a population pharmacokinetic (PK) approach. Rats were randomized in two groups receiving 1.5 mg iv oxaliplatin alone or 1.5 mg iv oxaliplatin under LIHI conditions, carrying out a hyperthermic 5% dextrose instillation. The oxaliplatin plasma concentrations were characterized by an open two-compartment PK model. RESULTS: Results concluded that surgical conditions affect the oxaliplatin elimination and distribution from blood to peripheral tissues, increasing the systemic drug exposure. Concretely, oxaliplatin peripheral volume of distribution, and clearance decreased by 48.6% and 55.3%, respectively, compared to the control group that resulted in a two-fold increase of the area under the concentration time curve. CONCLUSIONS: Comparison in clinical practice of oxaliplatin PK parameters obtained after iv administrations with those obtained after HIPEC interventions must be done carefully. This would limit the use of iv PK parameters to simulate new scenarios for oxaliplatin in HIPEC.

Pharmacokinetic and pharmacodynamic analysis of hyperthermic intraperitoneal oxaliplatin-induced neutropenia in subjects with peritoneal carcinomatosis.

The objective of this study was to characterize the pharmacokinetics and the time course of the neutropenia-induced by hyperthermic intraperitoneal oxaliplatin (HIO) after cytoreductive surgery in cancer patients with peritoneal carcinomatosis. Data from 30 patients who received 360 mg/m(2) of HIO following cytoreductive surgery were used for pharmacokinetic-pharmacodynamic (PK/PD) analysis. The oxaliplatin plasma concentrations were characterized by an open two-compartment pharmacokinetic model after first-order absorption from peritoneum to plasma. An oxaliplatin-sensitive progenitor cell compartment was used to describe the absolute neutrophil counts in blood. The reduction of the proliferation rate of the progenitor cells was modeled by a linear function of the oxaliplatin plasma concentrations. The typical values of oxaliplatin absorption and terminal half-lives were estimated to be 2.2 and 40 h, with moderate interindividual variability. Oxaliplatin reduced the proliferation rate of the progenitor cells by 18.2% per mg/L. No patient's covariates were related to oxaliplatin PK/PD parameters. Bootstrap and visual predictive check evidenced the model was deemed appropriate to describe oxaliplatin pharmacokinetics and the incidence and severity of neutropenia. A peritoneum oxaliplatin exposure of 65 and 120 mg·L/h was associated with a 20% and 33% incidence of neutropenia grade 4. The time course of neutropenia following HIO administration was well described by the semiphysiological PK/PD model. The maximum tolerated peritoneum oxaliplatin exposure is 120 mg L/h and higher exposures should be avoided in future studies. We suggest the prophylactic use of granulocyte colony stimulating factor for patients treated with HIO exposure higher than 65 mg L/h.

Semi-mechanistic model for neutropenia after high dose of chemotherapy in breast cancer patients.

PURPOSE: To describe the absolute neutrophil counts (ANC) profile in breast cancer patients receiving high-dose of chemotherapy and peripheral blood stem-cells (PBSC) transplantation. METHODS: Data from 41 subjects receiving cyclophosphamide, thiotepa and carboplatin were used to develop the ANC model consisting of a drug-sensitive progenitor cell compartment, linked to the peripheral blood compartment, through three transition compartments. PBSC were incorporated into the first transit compartment following a zero-order process, k(in), and the rebound effect was explained by a feedback mechanism. A 'kinetics of drug action' model was used to quantify the HDC effect on the progenitor cells according to a linear function, with a slope (alpha). RESULTS: The typical of the ANC at baseline (Circ(0)), mean transit time (MTT), feedback parameter (gamma), k(in) and alpha were estimated to be 5,610 x 10(6)/L, 3.25 days, 0.145, 0.954 cell/kg/day and 2.50 h/U, respectively. rHuG-CSF shortens the MTT by 92% and increases the mitotic activity by 120%. Bootstrap analysis, visual predictive check and numerical predictive checks evidenced accurate prediction of the ANC nadir, time to ANC nadir and time to grade 4 neutropenia recovery. CONCLUSION: The time course of neutropenia following high-dose of chemotherapy and PBSC transplantation was accurately predicted. Higher amount of CD34+ cells in the PBSC transplantation and earlier administration rHuG-CSF were associated with faster haematological recovery.

Computer simulations of bioequivalence trials: selection of design and analyte in BCS drugs with first-pass hepatic metabolism: linear kinetics (I).

Modeling and simulation approaches are useful tools to assess the potential outcome of different scenarios in bioequivalence studies. The aim of this study is to propose a new and improved semi-physiological model for bioequivalence trial simulations and apply it for all BCS (Biopharmaceutic Classification System) drug classes with non-saturated first-pass hepatic metabolism. The semi-physiological model was developed in NONMEM VI to simulate bioequivalence trials. Parent drug and metabolite levels for both reference and test were simulated. Eight types of drugs (with high or low permeability and high or low solubility (class I to IV) and high or low intrinsic clearance) were considered in two variability scenarios (high-low) and in six test products of decreasing biopharmaceutic quality. The scenarios were tested in single dose and steady state studies. In case of drugs with non-saturated hepatic first-pass effect (and no gut-wall metabolism) the parent drug is usually the most sensitive analyte and the single dose design is usually the most sensitive study design to detect the worsening of the biopharmaceutic quality of the test formulation. The only exception to this general conclusion was observed in class III drugs (high solubility, low permeability) with low intrinsic clearance for which the parent drug C(max) ratio in steady state shows higher sensitivity followed by the metabolite C(max) ratio in single dose. This exceptional behaviour is caused by a limited operative absorption time (or absorption window) in class III drugs that precludes complete absorption and produces a non-linear absorption. Therefore, it can be concluded that the metabolite does not need to be measured if the drug has no gut-wall metabolism and shows linear pharmacokinetics. Interestingly, a steady state study should be conducted in this exceptional case to compare with the highest possible sensitivity. Metabolite data in most of the scenarios either shows less sensitivity to the product characteristics (resulting in C(max) ratios passing the bioequivalence criteria when the products were not bioequivalent) or it gives the same information as the parent compound.

Population pharmacokinetics meta-analysis of plitidepsin (Aplidin) in cancer subjects.

OBJECTIVE: To characterize the population pharmacokinetics of plitidepsin (Aplidin) in cancer patients. METHODS: A total of 283 patients (552 cycles) receiving intravenous plitidepsin as monotherapy at doses ranging from 0.13 to 8.0 mg/m(2) and given as 1- or 24-h infusions every week; 3- or 24-h infusion biweekly; or 1-h infusion daily for 5 consecutive days every 21 days were included in the analysis. An open three-compartment pharmacokinetic model and a nonlinear binding to red blood cells model were used to describe the plitidepsin pharmacokinetics in plasma and blood, respectively, using NONMEM V software. The effect of selected covariates on plitidepsin pharmacokinetics was investigated. Model evaluation was performed using goodness-of-fit plots, posterior predictive check and bootstrap. RESULTS: Plasma clearance and its between subject variability (%) was 13.6 l/h (71). Volume of distribution at steady-state was calculated to be 4791 l (59). The parameters B (max) and C (50) of the non-linear blood distribution were 471 microg/l (56) and 41.6 microg/l, respectively. Within the range of covariates studied, age, sex, body size variables, aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), total bilirubin, creatinine clearance, albumin, total protein, performance status, co-administration of inhibitors or inducers of CYP3A4 and presence of liver metastases were not statistically related to plitidepsin pharmacokinetic parameters. Bootstrap and posterior predictive check evidenced the model was deemed appropriate to describe the time course of plitidepsin blood and plasma concentrations in cancer patients. CONCLUSIONS: The integration of phase I/II pharmacokinetic data demonstrated plitidepsin linear elimination from plasma, dose-proportionality up to 8.0 mg/m(2), and time-independent pharmacokinetics. The distribution to red blood cells can be considered linear at doses lower than 5 mg/m(2) administered as 3-h or longer infusion. No clinically relevant covariates were identified as predictors of plitidepsin pharmacokinetics.

Pharmacokinetic studies of linezolid and teicoplanin in the critically ill.

OBJECTIVES: To determine the pharmacokinetic characteristics of linezolid and teicoplanin in critically ill patients. PATIENTS AND METHODS: Serum was collected frequently during day 0 and then pre- and 1 h post-dose on days 1, 2, 3, 5, 7 and every third day thereafter during treatment. Serum linezolid concentrations were analysed using HPLC. Serum teicoplanin levels were analysed by fluorescence polarization immunoassay. RESULTS: A two-compartment model was required to characterize linezolid pharmacokinetics (n=28) and account for the accumulation seen after multiple dosing. The estimated clearance was 0.049 +/-0.016 L/h/kg (+/-s.e.m. of estimate). At steady state (dosing interval 12 h), linezolid serum concentrations exceeded the breakpoint of 4 mg/L for 10.88 h (95% CI 10.09-11.66) after a 600 mg dose with an AUC/MIC of 92.4 (95% CI 57.2-127.7). Teicoplanin was best described by a two-compartment model (n=26). The clearance was 4.97+/-1.58 L/h. Serum levels exceeded the breakpoint of 4 mg/L for the entire dosing interval in all subjects (400 mg dose every 12 h) with an AUC/MIC of 399.3 (95% CI 329.6-469.0). However, only four of 14 exceeded trough serum concentrations of 10 mg/L. For both agents, trough levels were similar in those who survived and those who died. CONCLUSIONS: Linezolid dosage at 600 mg every 12 h was adequate in the critically ill without need for adjustment for renal function. For teicoplanin, further study is needed to confirm if a trough of 10 mg/L is associated with a higher rate of cure than 5 mg/L. If so, serum drug assays would be needed to ensure a therapeutic level.

Assessment and modulation of acamprosate intestinal absorption: comparative studies using in situ, in vitro (CACO-2 cell monolayers) and in vivo models.

The purpose of this study was to explore the intestinal absorption mechanism of acamprosate and to attempt to improve the bioavailability (BA) of the drug through modulation of its intestinal absorption using two enhancers (polysorbate 80 and sodium caprate) based on in situ, in vitro and in vivo models and comparing the results obtained. Intestinal transport of the drug, in the absence and in presence of polysorbate 80 (0.06, 0.28 and 9.6 mM) or sodium caprate (13 and 16 mM) was measured by using an in situ rat gut technique and Caco-2 cell monolayers. Additionally, the effect of sodium caprate on drug oral bioavailability, measured as urinary recovery, was quantified by performing in vivo experiments with the rat as animal model. Only sodium caprate was able to increase the absorption rate constant (ka) of acamprosate in the mid-intestine of the rats from 0.29 +/- 0.07 h-1 in the absence of the promoter to 0.51 +/- 0.19 h-1 in the presence of C10 16 mM, along with the apparent permeability (Papp) obtained in Caco-2 cells (around two-fold). However, the drug bioavailability in rats (around 20%) did not improve in the presence of any of the concentrations tested (13, 16 and 50 mM). It is concluded that acamprosate absorption likely occurs via paracellular pathway and can be enhanced by sodium caprate in situ and in vitro but not in vivo-thus suggesting that although in situ and in vitro studies could be useful in early screening to select a potential promoter, in vivo studies in animal models are necessary to confirm the utility of the enhancer and to determine the influence of physiological variables.