1.
Ellfolk, Maria, 1976-
(författare)
Regulation of Vitamin D 25-hydroxylases : Effects of Vitamin D Metabolites and Pharmaceutical Compounds on the Bioactivation of Vitamin D
2008
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
A 700bp portion of the promoter of CYP2D25, the porcine microsomal vitamin D 25-hydroxylase was isolated and sequenced. The computer analysis of the sequence revealed the existence of a putative VDRE at 220 bp upstream of the transcription start site. A CYP2D25 promoter-luciferase reporter plasmid was constructed in order to study the transcriptional regulation of the gene. Treatment with the vitamin D metabolites calcidiol and calcitriol suppressed the promoter, provided that the nuclear receptors VDR and RXR were overexpressed. Phenobarbital was also capable of suppressing the promoter if the nuclear receptors PXR or CAR were overexpressed.The 25-hydroxylases are not expressed solely in liver but in a wide array of other organs as well. It is therefore possible at least in theory to study the vitamin D 25-hydroxylation in human subjects using cells from extrahepatic organs, from which biopsy retrieval is easier than from the liver. Dermal fibroblasts are frequently used to study different pathological conditions in human subjects and they are easy to come by. Dermal fibroblasts were shown to express two vitamin D 25-hydroxylases: CYP27A1 and CYP2R1. The expression pattern of CYP2R1 displayed considerable interindividual variation. The fibroblasts were also capable of measurable vitamin D 25-hydroxylation, which makes dermal fibroblasts a possible tool in studying vitamin D 25-hydroxylation in human subjects.Little is known about the regulation of expression and activity of the human vitamin D 25-hydroxylases. Therefore dermal fibroblasts – expressing CYP2R1 and CYP27A1 – and human prostate cancer LNCaP cells, that express CYP2R1 and CYP2J2, were treated with calcitriol and phenobarbital and efavirenz, two drugs that give rise to vitamin D deficiency. Treatment decreased the mRNA levels of CYP2R1 and CYP2J2 provided that the treated cells also expressed the necessary nuclear receptors. CYP27A1 did not respond to any of the treatments. The treatments also managed to decrease the 25-hydroxylating activity of the cells.The results show that vitamin D 25-hydroxylases can be regulated by both endogenous and xenobiotic compounds.
2.
Fransén, Nelly, 1978-
(författare)
Studies on a Novel Powder Formulation for Nasal Drug Delivery
2008
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
Nasal administration has potential for the treatment of indications requiring a fast onset of effect or for drugs with low oral bioavailability. Liquid nasal sprays are relatively common, but can be associated with suboptimal absorption from the nasal cavity; this thesis shows that nasal absorption can be significantly enhanced with a dry powder formulation. It was shown that interactive mixtures, consisting of fine drug particles adhered to the surface of mucoadhesive carrier particles, could be created in a particle size suitable for nasal administration. Sodium starch glycolate (SSG), a common tablet excipient, was used as carrier material. In vitro evaluation of the formulation indicated that the mucoadhesion of the carrier was unlikely to be affected by the addition of a drug. The powder formulation did not improve the in vitro transfer of dihydroergotamine across porcine nasal mucosa compared with a liquid formulation; however, the results were associated with methodological shortcomings. The binding of model substances to SSG and three other excipients was evaluated. Ion exchange interactions were for example detected between SSG and cationic drugs, but these interactions were most extensive at low salt concentrations and should unlikely affect in vivo bioavailability at physiological salt concentrations. Absorption of the peptide drug desmopressin from the SSG nasal formulation, from a novel sublingual tablet formulation and from a commercial nasal liquid spray was evaluated in a clinical trial. While no improvement over the liquid spray was seen with the sublingual tablet, plasma concentrations after the nasal powder formulation were three times higher than those after the liquid spray. All formulations were well accepted by the volunteers. The use of currently available mucoadhesive carrier particles in interactive mixtures offers potential for a new method of producing nasal powder formulations that should also be applicable to large scale production.
3.
Kjellsson, Maria C., 1975-
(författare)
Methodological Studies on Models and Methods for Mixed-Effects Categorical Data Analysis
2008
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
Effects of drugs are in clinical trials often measured on categorical scales. These measurements are increasingly being analyzed using mixed-effects logistic regression. However, the experience with such analyzes is limited and only a few models are used. The aim of this thesis was to investigate the performance and improve the use of models and methods for mixed-effects categorical data analysis. The Laplacian method was shown to produce biased parameter estimates if (i) the data variability is large or (ii) the distribution of the responses is skewed. Two solutions are suggested; the Gaussian quadrature method and the back-step method. Two assumptions made with the proportional odds model have also been investigated. The assumption with proportional odds for all categories was shown to be unsuitable for analysis of data arising from a ranking scale of effects with several underlying causes. An alternative model, the differential odds model, was developed and shown to be an improvement, in regard to statistical significance as well as predictive performance, over the proportional odds model for such data. The appropriateness of the likelihood ratio test was investigated for an analysis where dependence between observations is ignored, i.e. performing the analysis using the proportional odds model. The type I error was found to be affected; thus assessing the actual critical value is prudent in order to verify the statistical significance level. An alternative approach is to use a Markov model, in which dependence between observations is incorporated. In the case of polychotomous data such model may involve considerable complexity and thus, a strategy for the reduction of the time-consuming model building with the Markov model and sleep data is presented. This thesis will hopefully contribute to a more confident use of models for categorical data analysis within the area of pharmacokinetic and pharmacodynamic modelling in the future.
4.
Nordström, Josefina, 1977-
(författare)
Compression analysis as a tool for technical characterization and classification of pharmaceutical powders
2008
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
There are today strong incentives for an increased understanding of material properties and manufacturing processes to facilitate the development of new technologies in the pharmaceutical industry. The purpose of this thesis was to suggest methods requiring a low sample amount for characterization of technical properties of powders.Compression analysis was used to evaluate the formulation relevance of some compression equations. Using the mechanics of single granules to estimate powder functionality was part of this work. It was concluded that the formability of granular solids and the plasticity of single granules could be determined with compression analysis by using the Kawakita model for single components and binary mixtures of ductile granules.Further on, the fragmentation propensity of solid particles could be estimated from compression analysis by using the Shapiro equation, enabling indicators of both the fragmentation and the deformation propensity of particles to be derived in one single compression test.The interpretations of the compression parameters were only valid if the influence of particle rearrangement was negligible for the overall compression profile. An index indicating the extent of particle rearrangement was developed and a classification system of powders into groups dependent on the incidence of particle rearrangement was suggested as tools to enable rational interpretations of compression parameters.The application of compression analysis was demonstrated by investigating the relevance of the mechanics of granular solids for their tableting abilities. The plasticity of single gran-ules was suggested to influence both the rate of compactibility and the mode of deformation, and consequently the maximal tablet strength. The degree of granule bed deformation was shown to be a potential in line process indicator to describe the tableting forming ability.This thesis contributes to a scheme, suitable in formulation work and process control, to describe manufacturability of powders for an enhanced tablet formulation technology.
5.
Unga, Johan, 1976
(författare)
PEG and lipids in solid dispersions and liquid crystals - structure and phase behaviour
2008
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
In this thesis, two different kinds of nano-structured systems have been studied; solid dispersion systems of polyethylene glycol (PEG) and liquid crystalline systems containing the polar lipids monoolein (MO) and phytantriol (PT). Solid dispersions of PEG were studied with addition of different substances, lipids or parabens. The dispersions have been examined in the solid state, using differential scanning calorimetry and X-ray methods with the focus of the behaviour of the PEG carrier material. It was found that incorporation of MO increased with decreasing PEG molecular weight and that MO addition also affected the lamellae thickness of PEG. Different lipids affected the structure of PEG differently. To find which properties of the lipid that governed the behaviour of the solid dispersions twelve different lipids in PEG 4000 were examined. All lipids increased the fraction of the PEG that was in its folded conformation where small and hydrophilic lipids increased the folding the most. The unfolding of the folded form to unfolded was slower with lipids present in the PEG. Large and hydrophobic lipids like triolein and tristearin stabilized the folded form most effectively. The relation between solubility in a liquid PEG (PEG 400) and the structure of PEG 4000 solid dispersions was examined using a homologous series of parabens (methyl- to butyl- paraben). A high solubility in liquid PEG correlated to a high solubility in the solid dispersions and a larger increase of the lamellae thickness. The thickening of the lamellae was shown to be due to a swelling of the amorphous domains of the structure.The studies of the liquid crystalline phases of MO and PT revealed large similarities. The two-component lipid-water systems are almost identical with the difference that the PT phases swell much less. In three component solvent-lipid-water systems (solvents: propylene glycol (PG), polyethylene glycol 400 (PEG 400) and 2-methyl-2,4-pentanediol (MPD)) the same differences could be seen between PT and MO where PT phases swelled less than MO. One other major difference was the formation of L3 phase. With MO L3 phase was found in all three solvent systems whereas it with PT was only found in the system with MPD, the most hydrophobic solvent. The differences between the PT and MO systems were explained by the fact that PT is more hydrophobic and forms less flexible bilayers.
