Pharmacokinetics of aztreonam in healthy subjects and patients with cystic fibrosis and evaluation of dose-exposure relationships using monte carlo simulation.

Aztreonam (AZM) is a monobactam antibiotic with a high level of activity against gram-negative micro-organisms, including Pseudomonas aeruginosa. We evaluated AZM pharmacokinetics and pharmacokinetic-pharmacodynamic relationships in patients with cystic fibrosis (CF) and healthy subjects. Pharmacokinetic data in eight CF patients and healthy subjects that were matched for age, gender, weight, and height were obtained and analyzed by using the nonparametric adaptive grid algorithm.

Pharmacokinetics of mycophenolate mofetil in hematopoietic stem cell transplant recipients.

Mycophenolate mofetil (MMF), a prodrug of mycophenolic acid (MPA), is increasingly used in the prophylaxis of graft-versus-host disease (GVHD) after hematopoietic stem cell transplantation (HCT). Few pharmacokinetic data are available about the use of MMF for this indication. This case series aimed at analyzing the pharmacokinetics of MMF in a population of HCT recipients representative for everyday practice.

Therapeutic drug monitoring of mycophenolic acid: does it improve patient outcome?

Treatment with the immunosuppressive agent mycophenolate mofetil (MMF) decreases the risk of rejection after renal transplantation and improves graft survival compared with azathioprine. The exposure to the active metabolite mycophenolic acid (MPA) is correlated to the risk of developing acute rejection. The interpatient variability in exposure of MPA is wide relative to the proposed therapeutic window of the MPA AUC(0 12) (30 - 60 mg.

Medicinal cannabis does not influence the clinical pharmacokinetics of irinotecan and docetaxel.

Objective: To date, data regarding the potential of cannabinoids to modulate cytochrome P450 isozyme 3A (CYP3A) activity are contradictory. Recently, a standardized medicinal cannabis product was introduced in The Netherlands. We anticipated an increased use of medicinal cannabis concurrent with anticancer drugs, and undertook a drug-interaction study to evaluate the effect of concomitant medicinal cannabis on the pharmacokinetics of irinotecan and docetaxel, both subject to CYP3A-mediated biotransformation.

Influence of ketoconazole on the fecal and urinary disposition of docetaxel.

Objective: The anticancer drug docetaxel is extensively metabolized by cytochrome P450 (CYP) 3A isozymes. Furthermore, docetaxel is also a substrate for the transmembrane ATP-binding cassette efflux transporter protein ABCB1. CYP3A-inhibition significantly reduces docetaxel total systemic clearance, on average by 50%.

Time-dependent clearance of mycophenolic acid in renal transplant recipients.

Aims: Pharmacokinetic studies of the immunosuppressive compound mycophenolic acid (MPA) have shown a structural decrease in clearance (CL) over time after renal transplantation. The aim of this study was to characterize the time-dependent CL of MPA by means of a population pharmacokinetic meta-analysis, and to test whether it can be described by covariate effects.

Methods: One thousand eight hundred and ninety-four MPA concentration-time profiles from 468 renal transplant patients (range 1-9 profiles per patient) were analyzed retrospectively by nonlinear mixed effect modelling.

Nicardipine in pre-eclamptic patients: placental transfer and disposition in breast milk.

To assess the safety risks to the fetus and neonate caused by maternal use of nicardipine in pre-eclamptic patients, we evaluated the placental transfer and the transfer to breast milk after maternal intravenous administration of nicardipine. In ten pre-eclamptic subjects, nicardipine concentrations of maternal blood (P) and both arterial and venous umbilical cord blood samples (Uarterial and Uvenous) were assessed, and the U/P ratio was calculated as an indication of placental transfer. We found a median transfer of 0.

Alternative drug formulations of docetaxel: a review.

The anticancer drug docetaxel (Taxotere) is formulated in the nonionic surfactant polysorbate 80 (Tween 80). Early in the clinical development of docetaxel, it became clear that docetaxel administration is associated with the occurrence of unpredictable (acute) hypersensitivity reactions and cumulative fluid retention. These side-effects have been attributed, in part, to the presence of polysorbate 80 and have consequently initiated research focused on the development of a less-toxic, better-tolerated polysorbate 80-free formulation of docetaxel.

Pharmacokinetics and pharmacodynamics of midazolam and metabolites in nonventilated infants after craniofacial surgery.

Background: Because information on the optimal dose of midazolam for sedation of nonventilated infants after major surgery is scant, a population pharmacokinetic and pharmacodynamic model is developed for this specific group.

Methods: Twenty-four of the 53 evaluated infants (aged 3-24 months) admitted to the Pediatric Surgery Intensive Care Unit, who required sedation judged necessary on the basis of the COMFORT-Behavior score and were randomly assigned to receive midazolam, were included in the analysis. Bispectral Index values were recorded concordantly.

Influence of high-dose ketoconazole on the pharmacokinetics of docetaxel.

Objective: The pharmacokinetics (PK) of docetaxel are characterized by large inter-individual variability in systemic drug exposure (AUC) and drug clearance. The PK variability is thought to be largely related to differences in the catalytic function of CYP3A, involved in docetaxel metabolism and elimination. As variability in efficacy and toxicity is associated with variability in docetaxel AUC and clearance, reducing inter-individual PK variability may help improve the risk-benefit ratio of docetaxel therapy.

Population pharmacokinetics and pharmacodynamics of nelfinavir and its active metabolite M8 in HIV-1-infected children.

Background: The objectives of this study are to develop and validate a population pharmacokinetic model that adequately describes the pharmacokinetics of nelfinavir and its active metabolite M8 in HIV-1-infected children; to define factors involved in the pharmacokinetic variability, which could aid in defining dosing strategies; and to correlate the pharmacokinetics to the treatment response.

Methods: Protease inhibitor-naive, HIV-1-infected children were included. A population pharmacokinetic model of nelfinavir and M8 was developed using NONMEM.

Individualization of mycophenolate mofetil dose in renal transplant recipients.

The immunosuppressive agent mycophenolate mofetil has been successfully used over the past 10 years to prevent acute allograft rejection after renal transplantation. It has mainly been administered as a fixed dose of mycophenolate mofetil 1000 mg b.i.

Caspofungin: antifungal activity in vitro, pharmacokinetics, and effects on fungal load and animal survival in neutropenic rats with invasive pulmonary aspergillosis.

Objectives: Evaluation of the potential of caspofungin, in relation to pharmacokinetics, in order to optimize its use in the treatment of filamentous fungal infections.

Methods: The in vitro antifungal activity, pharmacokinetics and therapeutic efficacy of caspofungin versus amphotericin B was investigated in vitro as well as in a model of aerogenic Aspergillus fumigatus infection in neutropenic rats, using rat survival and decrease in fungal burden as parameters for therapeutic efficacy.

Results: In contrast to amphotericin B, caspofungin shows a concentration-dependent gradual decrease in fungal growth in vitro, which makes it difficult to perform visual readings of antifungal activity (CLSI guidelines).

Explaining variability in mycophenolic acid exposure to optimize mycophenolate mofetil dosing: a population pharmacokinetic meta-analysis of mycophenolic acid in renal transplant recipients.

Large between- and within-patient variability has been observed in the pharmacokinetics of mycophenolic acid (MPA). However, conflicting results exist about the influence of patient characteristics that explain the variability in MPA exposure. This population pharmacokinetic meta-analysis of MPA in renal transplant recipients was performed to explore whether race, renal function, albumin level, delayed graft function, diabetes, and co-medication are determinants of total MPA exposure.

Within-patient variability of mycophenolic acid exposure: therapeutic drug monitoring from a clinical point of view.

Exposure to mycophenolic acid (MPA) is highly variable among patients on standard dose mycophenolate mofetil (MMF) therapy. In addition, MPA exposure increases with time posttransplant and exposure is predictive for the development of acute rejection. Consequently, therapeutic drug monitoring (TDM) of MPA may improve clinical outcome, although a large within-patient variability could be a limitation.

Population pharmacokinetics of mycophenolic acid in renal transplant recipients.

Background: Mycophenolate mofetil is the prodrug of mycophenolic acid (MPA) and is used as an immunosuppressant following renal, heart, lung and liver transplantation. Although MPA plasma concentrations have been shown to correlate with clinical outcome, there is considerable inter- and intrapatient pharmacokinetic variability. Consequently, it is important to study demographic and pathophysiological factors that may explain this variability in pharmacokinetics.

Estimation of the glomerular filtration rate in children: which algorithm should be used?

Glomerular filtration rate (GFR) in children can be estimated by the formula GFR=k x BH/Pcr (where BH is body height in centimetres and Pcr is the plasma creatinine concentration in micromoles per litre). For k, several values have been reported: k=38 (Counahan), k=40 (Morris) and k=48.7 (Schwartz).

Potential for improvement of docetaxel-based chemotherapy: a pharmacological review.

Since the introduction of docetaxel, research has focused on various approaches to overcome treatment limitations and improve outcome. This review discusses the pharmacological attempts at treatment optimisation, which include reducing interindividual pharmacokinetic and pharmacodynamic variability, optimising schedule, route of administration, reversing drug resistance and the development of structurally related second-generation taxanes.

Semi-physiological model describing the hematological toxicity of the anti-cancer agent indisulam.

Indisulam (N-(3-chloro-7-indolyl)-1,4-benzenedisulfonamide, GOAL, E7070) is a novel anti-cancer drug currently in phase II clinical development for the treatment of solid tumors. Phase I dose-escalation studies were conducted comparing four treatment schedules. Neutropenia and thrombocytopenia were dose limiting in all schedules.

Cyclosporine interacts with mycophenolic acid by inhibiting the multidrug resistance-associated protein 2.

In mycophenolate mofetil (MMF)-treated organ transplant recipients, lower mycophenolic acid (MPA) plasma concentrations have been found in cyclosporine (CsA) compared with tacrolimus (Tac)-based immunosuppressive regimens. We previously demonstrated that CsA decreases exposure to MPA and increases exposure to its metabolite MPA-glucuronide (MPAG), possibly by interfering with the biliary excretion of MPAG. To elucidate the role of the multidrug resistance-associated protein (Mrp)-2 in the interaction between MMF and CsA, we treated three groups of 10 Mrp2-deficient rats (TR- rat) for 6 days with either vehicle, CsA (8 mg/kg) or Tac (4 mg/kg) by oral gavage.

Predicting the usefulness of therapeutic drug monitoring of mycophenolic acid: a computer simulation.

The usefulness of therapeutic drug monitoring (TDM) of mycophenolate mofetil (MMF) was investigated with a computer simulation model. For a fixed-dose (FD) and a concentration-controlled (CC) MMF dosing regimen exposure to mycophenolic acid (MPA) was compared. A nonlinear mixed-effects model (NONMEM) for MPA based on extensive pharmacokinetic data from 140 renal transplant recipients who all used cyclosporine and corticosteroids as maintenance immunosuppressive therapy provided Bayesian estimates for MPA oral clearance on 9 occasions during the first 24 weeks after transplantation.

Population pharmacokinetics of cyclosporine in kidney and heart transplant recipients and the influence of ethnicity and genetic polymorphisms in the MDR-1, CYP3A4, and CYP3A5 genes.

Objective: Our objective was to determine the relationship between single nucleotide polymorphisms (SNPs) in the multidrug resistance 1 (MDR-1) gene and the cytochrome P450 (CYP) genes CYP3A4 and CYP3A5 and the pharmacokinetics of cyclosporine (INN, ciclosporin).

Methods: Cyclosporine pharmacokinetics of 151 kidney and heart transplant recipients undergoing maintenance therapy was described by use of nonlinear mixed-effects modeling (NONMEM) according to a 2-compartment pharmacokinetic model with first-order absorption and elimination. All patients were genotyped for the CYP3A4*1B and *3 , CYP3A5*3 and *6 , and MDR-1 3435C-->T SNPs.

Mycophenolic acid in diabetic renal transplant recipients: pharmacokinetics and application of a limited sampling strategy.

Limited sampling strategies may be useful in optimizing therapeutic drug monitoring of mycophenolic acid (MPA). Their use, however, may be limited by several patient factors, including comorbidity. In this study the pharmacokinetics of MPA in diabetic and nondiabetic renal transplant recipients were compared, and it was evaluated whether a limited sampling strategy developed and validated for nondiabetic patients can also be used in diabetic patients.