No description available.

No description available.

No description available.

No description available.

Itraconazole is a triazole antifungal used in the treatment of allergic bronchopulmonary aspergillosis (ABPA) in patients with cystic fibrosis (CF) and for the prevention of invasive fungal infections in paediatric patients undergoing bone marrow transplants (BMT). The pharmacokinetic (PK) properties of this drug and its active metabolite have been described before; however, there is only sparse information available of the PK properties of this drug in the general paediatric population and CF patients in particular. Even though the target concentrations to obtain treatment success from this drug in ABPA have not been established, therapeutic drug monitoring has been shown to be necessary due to a high interpatient variability and low concentrations reported in these patient groups. The general aim of this thesis was to use modelling approaches to provide a better understanding of the PK of itraconazole, in particular to investigate the relative bioavailability of the two commercial formulations (capsule and oral solution), and to attempt to evaluate relationships between patient characteristics and parameters to enable better individualised therapy to maximise the benefits of this drug. The first study was a paediatric population PK (popPK) investigation of itraconazole and its active metabolite hydroxy-itraconazole in CF and BMT patients. All paediatric CF or BMT patients taking oral itraconazole for therapeutic reasons were eligible for the study. A minimum of two blood samples were drawn after the capsules and also after switching to oral solution, or vice versa. Itraconazole and hydroxy-itraconazole plasma concentrations were measured by a newly developed and validated high-performance liquid chromatography. A nonlinear mixed-effects modelling approach (NONMEM 5.1.1) was used to describe the PK of itraconazole and hydroxy-itraconazole simultaneously. A 1-compartment model with first order absorption and elimination best described itraconazole kinetics, with first order conversion to hydroxy-itraconazole. For itraconazole, the apparent clearance and volume of distribution was 35.5 L/h and 672 L, respectively; the absorption rate constant for the capsule formulation was 0.0901 h¯¹ and for the oral solution formulation it was 0.959 h¯&sup1. The relative bioavailability for the capsules was 0.55. Of several screened covariates, only allometrically scaled total body weight significantly improved the fit to the data. No difference between the two populations was found. High inter-patient variability confirmed previous data in CF, leukaemia and BMT patients. From the population model, simulations were performed to develop more adequate dosage regimens to achieve target therapeutic trough plasma concentration of 0.5 mg/L. Higher doses of itraconazole than presently used are needed in these patients, particularly when it is prescribed as capsules. To further support the aims of the thesis, a popPK study with oral itraconazole and its active metabolite in adult patients with CF for capsule and oral solution was performed. A D-optimal study design was developed in MATLAB using POPT v. 2.0, B, which was based on the administration of solution and capsules to 30 patients in a cross-over design. Eight blood samples were taken on two occasions as per the optimal sampling design and assayed by HPLC. NONMEM (5.1.1) was used for the popPK analysis. A total of 241 blood samples were collected, of which 94% were taken within the defined optimal sampling window. A 2-compartment model with first order absorption and elimination best described itraconazole kinetics, with first order formation for metabolism to the hydroxy-metabolite. Absorption rate constants for capsule and solution were 0.0315 h¯¹ and 0.125 h¯¹, respectively. The comparative bioavailability of the capsule to solution was 0.82 in this study. There was no evidence of nonlinearity in the PK of itraconazole and no screened covariate significantly improved the fit to the data. There was high inter-patient variability confirmed previous results in CF. The optimal design performed well for estimation of model parameters from a complex parent-metabolite popPK model. Due to the sampling windows, most of the samples could be collected within the daily hospital routine, but at times that were “near-optimal” for estimating the popPK parameters. Simulations from the final model showed that the current dosing regimen of 200 mg twice daily would provide a trough target concentration at steady state in only 35% of patients when administered as the solution, and 31% when administered as the capsules. The optimal dosing schedule was 500 mg b.d. for both formulations. Since the therapeutic target for itraconazole, is still unresolved, the potential risks of these dosing schedules need to be assessed on an individual basis. This thesis provides information on several methods and their applications to sparse sampling population pharmacokinetic studies and offers results and future directions to maximize the benefits of itraconazole therapy. The population modelling approach has been successfully applied to both clinical studies.

Itraconazole is a triazole antifungal used in the treatment of allergic bronchopulmonary aspergillosis (ABPA) in patients with cystic fibrosis (CF) and for the prevention of invasive fungal infections in paediatric patients undergoing bone marrow transplants (BMT). The pharmacokinetic (PK) properties of this drug and its active metabolite have been described before; however, there is only sparse information available of the PK properties of this drug in the general paediatric population and CF patients in particular. Even though the target concentrations to obtain treatment success from this drug in ABPA have not been established, therapeutic drug monitoring has been shown to be necessary due to a high interpatient variability and low concentrations reported in these patient groups. The general aim of this thesis was to use modelling approaches to provide a better understanding of the PK of itraconazole, in particular to investigate the relative bioavailability of the two commercial formulations (capsule and oral solution), and to attempt to evaluate relationships between patient characteristics and parameters to enable better individualised therapy to maximise the benefits of this drug. The first study was a paediatric population PK (popPK) investigation of itraconazole and its active metabolite hydroxy-itraconazole in CF and BMT patients. All paediatric CF or BMT patients taking oral itraconazole for therapeutic reasons were eligible for the study. A minimum of two blood samples were drawn after the capsules and also after switching to oral solution, or vice versa. Itraconazole and hydroxy-itraconazole plasma concentrations were measured by a newly developed and validated high-performance liquid chromatography. A nonlinear mixed-effects modelling approach (NONMEM 5.1.1) was used to describe the PK of itraconazole and hydroxy-itraconazole simultaneously. A 1-compartment model with first order absorption and elimination best described itraconazole kinetics, with first order conversion to hydroxy-itraconazole. For itraconazole, the apparent clearance and volume of distribution was 35.5 L/h and 672 L, respectively; the absorption rate constant for the capsule formulation was 0.0901 h¯¹ and for the oral solution formulation it was 0.959 h¯&sup1. The relative bioavailability for the capsules was 0.55. Of several screened covariates, only allometrically scaled total body weight significantly improved the fit to the data. No difference between the two populations was found. High inter-patient variability confirmed previous data in CF, leukaemia and BMT patients. From the population model, simulations were performed to develop more adequate dosage regimens to achieve target therapeutic trough plasma concentration of 0.5 mg/L. Higher doses of itraconazole than presently used are needed in these patients, particularly when it is prescribed as capsules. To further support the aims of the thesis, a popPK study with oral itraconazole and its active metabolite in adult patients with CF for capsule and oral solution was performed. A D-optimal study design was developed in MATLAB using POPT v. 2.0, B, which was based on the administration of solution and capsules to 30 patients in a cross-over design. Eight blood samples were taken on two occasions as per the optimal sampling design and assayed by HPLC. NONMEM (5.1.1) was used for the popPK analysis. A total of 241 blood samples were collected, of which 94% were taken within the defined optimal sampling window. A 2-compartment model with first order absorption and elimination best described itraconazole kinetics, with first order formation for metabolism to the hydroxy-metabolite. Absorption rate constants for capsule and solution were 0.0315 h¯¹ and 0.125 h¯¹, respectively. The comparative bioavailability of the capsule to solution was 0.82 in this study. There was no evidence of nonlinearity in the PK of itraconazole and no screened covariate significantly improved the fit to the data. There was high inter-patient variability confirmed previous results in CF. The optimal design performed well for estimation of model parameters from a complex parent-metabolite popPK model. Due to the sampling windows, most of the samples could be collected within the daily hospital routine, but at times that were “near-optimal” for estimating the popPK parameters. Simulations from the final model showed that the current dosing regimen of 200 mg twice daily would provide a trough target concentration at steady state in only 35% of patients when administered as the solution, and 31% when administered as the capsules. The optimal dosing schedule was 500 mg b.d. for both formulations. Since the therapeutic target for itraconazole, is still unresolved, the potential risks of these dosing schedules need to be assessed on an individual basis. This thesis provides information on several methods and their applications to sparse sampling population pharmacokinetic studies and offers results and future directions to maximize the benefits of itraconazole therapy. The population modelling approach has been successfully applied to both clinical studies.

No description available.

No description available.

Alzheimer's disease (AD) is a progressive neurodegenerative disorder, which is characterised clinically by dementia and progressive memory loss, and pathologically by neuronal degeneration, plaques (insoluble β-amyloid (Aβ) protein) and neurofibrillary lesions (abnormally phosphorylated tau protein). The mechanisms by which cells die in AD remain largely unknown and controversial. There is some evidence to suggest that cell death in AD brains may occur by apoptosis, and that Aβ might be involved in this process. Apoptosis, a type of cell death characterised by distinct morphological and biochemical features, is often the result of 'programmed cell death' (PCD). Many gene families have been proposed to be involved in the PCD pathway, including the caspase family, inducible transcription factor (ITF) family (including Jun, Fos and Krox genes), and members of the Bcl-2 gene family (including the death promoting gene Bax). It is possible, therefore, that some of these genes may play a role in cell death in AD. The hippocampus is one of the first regions of the brain to be affected in AD, showing cell loss mainly in the CA1-2 pyramidal cell layer. In this thesis, the hippocampus from AD and Control cases has been examined for markers of apoptosis and genes thought to be involved in PCD. In addition, the actions of Aβ, human amylin (a structurally similar protein to Aβ) and the Aβ precursor protein (APP) have been examined in cell culture in an attempt to elucidate their mechanisms of action and relate this to the pathogenesis of AD. AD hippocampi showed increased DNA fragmentation as assessed by TdT-mediated dUTP-biotin nick end labelling (TUNEL), but TUNEL-positive cells in AD generally did not exhibit 'typical' apoptotic morphology, and there was no evidence of the oligonucleosomal DNA fragmentation characteristic of apoptosis. This indicates that 'typical' apoptosis may not be the predominant cell death mechanism in AD. However, there was some evidence of atypical 'broken' nuclei, which may represent a form of apoptosis that presents with a different morphology in aging tissue. This study found no conclusive evidence of increased expression of Fos or Jun family members in the CA1 region of AD hippocampi, however there were increased levels of the putative 'apoptosis-specific protein' and krox24 mRNA in this area which could be related to the cell death. There was no change in Bax expression in the CA1 region of AD brains (although increased Bax expression was observed in this region in a rat hypoxic-ischemia model where the CA1 neurons die by apoptosis). However, there was a decrease in Bax expression in the granule cells of AD hippocampi which could be related to the relative preservation of these cells in AD. Bax and ITF expression was observed in tangles, senile plaques and Hirano bodies in AD hippocampi, which may be related to the formation of these features and/or the pathogenesis of AD. There appeared to be changes in the cellular location of proteins in post-mortem tissue that made determination of ITF levels extremely difficult. In addition, patterns of ITF expression differed when different antisera directed at the same protein were used. These observations indicate that caution must be exercised when studying protein changes in post-mortem tissue. Application of insoluble Aβ to cultured cells, and overexpression of APP or familial AD-linked APP mutants in cultured cells, did not cause toxicity or alter c-Jun gene expression. However, human amylin was toxic to cultured cells, and had different effects on c-Jun gene expression depending on the cell type. This shows that structurally similar proteins do not always act by a similar mechanism, and that care must be taken when choosing a cell culture system to study disease-related events. The finding that neither insoluble Aβ nor APP/AD-linked APP mutants caused acute toxicity to cultured cells, coupled with the lack of relationship between TUNEL staining and Aβ deposits in post-mortem AD tissue, indicates that deposited insoluble Aβ and/or increased amounts of Aβ may not represent the toxic event in AD. This thesis provides a detailed investigation of several factors that could be involved in the cell death process in the hippocampus in AD. The results presented find no conclusive evidence for ‘classical’ apoptosis and/or increased ITF expression in the hippocampus in AD, but the changes in expression of krox24 mRNA, ‘apoptosis-specific protein’ and Bax suggest that programmed cell death may well be a mechanism which is involved in the pathogenesis of AD. / Whole document restricted, see Access Instructions file below for details of how to access the print copy. / Related published articles. MacGibbon GA, Cooper GJS, Dragunow M. Acute application of human amylin, unlike β-amyloid peptides, kills undifferentiated PC12 cells by apoptosis. NeuroReport 1997; 8:3945-3950. MacGibbon GA, Lawlor PA, Walton M, et al. Expression of Fos, Jun and Krox family proteins in Alzheimer's disease. Exp Neurol 1997; 147:316-332. MacGibbon GA, Lawlor PA, Sirimanne E et al. Bax expression in mammalian neurons undergoing apoptosis, and in Alzheimer's disease hippocampus. Brain Res 1997; 750:223-234

No description available.