Thèse (M.Sc.)--Université Laval, 2007. / Bibliogr.: f. 100-108. Publié aussi en version électronique dans la Collection Mémoires et thèses électroniques.

We present results of molecular simulations, quantum mechanical calculations, and experimental data aimed towards the rational design of solvent formulations. In particular, we have found that the rate limitation of oxidation of methionine groups is determined by the breaking of O-O bonds in hydrogen peroxide, not by the rate of acidic catalysis as previously thought. We have used this understanding to design molecular level parameters which are correlated to experimental data. Rate data has been determined both for G-CSF and for hPTH(1-34). / Singapore-MIT Alliance (SMA)

Είναι γνωστό ότι τα λιποσώματα παρέχουν πολλά πλεονεκτήματα για τη χορήγηση και /ή τη στόχευση φαρμάκων (Lasic 1993, Gregoriadis 1988). Κατά τη χορήγηση λιποσωμικών φαρμακομορφών για τοπική (topical) εφαρμογή ή εφαρμογή σε επιθήλια (mucosal) (Rollan 1993, Schreier and Bouwstra 1994) είναι απαραίτητο οι ρεολογικές και βλεννοσυγκολητικές ιδιότητες των λιποσωμικών διασπορών να ρυθμίζονται ανάλογα με την επιδιωκόμενη οδό χορήγησης. Αυτό μπορεί εύκολα να επιτευχθεί με τη προσθήκη παραγόντων αύξησης ιξώδους (gelling agents) στις λιποσωμικές διασπορές. Συνεπώς προκύπτουν σύνθετες φαρμακοτεχνικές μορφές που από δομικής σύστασης είναι διασπορές λιποσωμικών μορφών φάρμακων σε συστήματα γελών (drug-in-liposome-in-gel). Ανάλογα με το βαθμό συγκράτησης του φαρμάκου στα λιποσώματα μετά τη διασπορά των λιποσωμάτων στην επιθυμητή φαρμακοτεχνική μορφή, μπορεί να τροποποιηθεί και ο ρυθμός απελευθέρωσης του φαρμάκου από τέτοια συστήματα. Αυτό συνδέεται σε μεγάλο βαθμό κυρίως με δύο ομάδες παραγόντων: • Πρώτον με τη σταθερότητα των λιποσωμάτων (ακεραιότητα μεμβράνης και μηχανική σταθερότητα) κατά τη διασπορά σε ημι-στερεές φαρμακοτεχνικές μορφές, κάτι το οποίο συνδέεται τόσο με την σκληρότητα (rigidity) της μεμβράνης του λιποσωμικού φορέα όσο και με τις φυσικές ιδιότητες του ημι-στερεού συστήματος (ιξώδες και ρεολογικές ιδιότητες). • Δεύτερον, με τις φυσικοχημικές ιδιότητες του προς μορφοποίηση φάρμακου. Όσο πιο λιπόφιλο είναι ένα φάρμακο και όσο μικρότερη η διαλυτότητα του στο νερό, τόσο μεγαλύτερος θα είναι λογικά ο χρόνος συγκράτησης του στις λιπιδικές διπλοστοιβάδες των λιποσωμάτων συγκριτικά με αμφίφιλα φάρμακα που έχουν σημαντικά υψηλότερη διαλυτότητα στο νερό. Επειδή σε ανάλογα σύνθετα (φάρμακο-σε-λιπόσωμα-σε-γέλες) συστήματα χορήγησης είναι πιθανόν να πρέπει να συνυπάρχουν εκτός από τον παράγοντα αύξησης του ιξώδους και άλλα έκδοχα, κυρίως παράγοντες που αυξάνουν τη διαλυτότητα διάφορων ουσιών ή επιφανειοδραστικά, ο σκοπός της παρούσας μελέτης ήταν η εξέταση της επίδρασης τέτοιων εκδοχών κατά την προσθήκη τους στα παραπάνω συστήματα. Πιο συγκεκριμένα μελετήθηκε η επίδραση των εξής εκδόχων: Transcutol, Propylene-glycol, Cremophor και Labrafac στη σταθερότητα λιποσωμικών μορφών φαρμάκων και στο ρυθμό απελευθέρωσης υδρόφιλων και λιπόφιλων μορίων από συστήματα διασποράς λιποσωμικών μορφών τέτοιων ουσιών σε γέλες (drug-in-liposome-in-gel). Τα έκδοχα αυτά μόνα ή σε συνδυασμό μεταξύ τους καθως και σε συνδυασμό με άλλους φορείς προσφέρονται για την παρασκευή κατάλληλων φαρμακοτεχνικών μορφών που αποβλέπουν στην αύξηση διαλυτότητας, απορρόφησης και τελικά της βιοδιαθεσιμότητας δυσδιάλυτων φαρμάκων Για την εκτίμηση του βαθμού επίδρασης των πιο πάνω αναφερθέντων εκδοχών στη σταθερότητα λιποσωμικών μορφών φαρμάκων και στο ρυθμό απελευθέρωσης τόσο των υδρόφιλων όσο και λιπόφιλων φάρμακων από συστήματα διασποράς λιποσωμικών μορφών τους σε γέλες (drug-in-liposome-in-gel). χρησιμοποιήθηκε ως μοντέλο υδρόφιλων μορίων η καλσεΐνη ενώ ως μοντέλο υδρόφοβων ουσιών η γκριζεοφουλβίνη. Εδώ ως παράγοντες αύξησης του ιξώδους για την παρασκευή των σύνθετων φαρμακευτικών μορφών, φάρμακο-σε-λιπόσωμα-σε-γέλες χρησιμοποιήθηκαν: (Ι) το πολυμερές του ακρυλικού οξέος, carbopol 974PNF, (ΙΙ) το πολυμερές υδροξυ-αιθυλ-κυτταρίνης (HEC-Hydroxyethylcellulose) καθως και (ΙΙΙ) μίγμα των δυο πολυμερών. Γενικά από τη μελέτη αυτή συμπεραίνουμε ότι: Η επίδραση των προς εξέταση παραγόντων στη σταθερότητα των λιποσωμάτων εξαρτάται από: τη λιπιδική σύσταση, την προσθήκη χοληστερόλης κατά την παρασκευή των λιποσωμάτων, τη λιποφιλικότητα του εκδόχου και τη συγκέντρωσή του. Σχετικά με τη σταθερότητα των λιποσωμάτων παρουσία των εκδόχων που μελετήθηκαν: 1. Tα PC λιποσώματα σπάνε πολύ εύκολα με και χωρίς την παρουσία των εκδοχών στο φορέα υδρογέλης. 2. Τα πιο ανθεκτικά λιποσώματα DSPC/Chol 1:1 φαίνεται να έχουν μεγαλύτερη σταθερότητα. Όμως και στις δυο περιπτώσεις (PC και DSPC/Chol) η σταθερότητα των λιποσωμάτων στους παράγοντες αυτούς μειώνεται ακολουθώντας την εξής σειρά: Transcutol ≈ Propylene-glycol < Cremophor < Labrafac. 3. To Labrafac διαταράσσει στο μεγαλύτερο βαθμό τις λιπιδικές διπλοστοιβάδες προκαλώντας τη μεγαλύτερη διαρροή των εγκλωβισμένων μορίων προκαλώντας σημαντικές δομικές μεταβολές στα λιποσώματα. 4. H χοληστερόλη αυξάνει την σταθερότητα των λιποσωμάτων κυρίως παρουσία των εκδοχών με μια σχετική ασθενή δράση αλλά όχι σημαντικά παρουσία του εκδόχου Labrafac. Σχετικά με τη κινητική απελευθέρωσης ουσιών από λιποσωμικές τους μορφές που διασπείρονται σε γέλες παρουσία των εκδόχων που μελετήθηκαν: 1. Ένα σημαντικό εύρημα είναι ότι υπάρχει μεγάλη διαφορά στη συμπεριφορά απελευθέρωσης λιπόφιλων και υδρόφιλων μορίων από λιποσωμικές μορφές τους όταν τα τελευταία διασπείρονται σε συστήματα υδρογέλων παρουσία και απουσία των εκδόχων καθως και στη μεταξύ τους απελευθέρωση. 2. Σε γενικές γραμμές η απελευθέρωση των εγκλωβισμένων στα λιποσώματα ουσιών, όταν αυτά διασπείρονται στις γέλες που περιέχουν έκδοχα, φαίνεται να συνδέεται-επηρεάζεται από τη σταθερότητα των λιποσωμάτων παρουσία αυτών των εκδόχων, όπως ευρέθηκε στο πρώτο μέρος της μελέτης. Η κινητική απελευθέρωσης λιπόφιλων φαρμάκων από σύνθετα συστήματα όπως αυτά που μελετήθηκαν μπορεί να επιβραδύνεται σημαντικά όταν μέσα στις μορφές προστίθενται έκδοχα με υψηλή λιπόφιλα (Labrafac- γκριζεοφουλβίνη) (πιθανή κατανομή της γκριζεοφουλβίνης σε λιπόφιλες περιοχές). Κλείνοντας επισημαίνουμε ότι η ανακάλυψη νέων συστημάτων χορήγησης φαρμάκων αποτελεί σήμερα τη μεγαλύτερη πρόκληση για τους επιστήμονες. Οι πιο πάνω φορείς συγκαταλέγονται ανάμεσα στα πιο σπουδαία συστήματα χορήγησης φαρμάκων όχι μόνο λόγω συμβατότητας τους ως προς το ανθρώπινο οργανισμό αλλά και εξαιτίας της μεγάλης δυνατότητας εφαρμογών που προσφέρουν. Απώτερος σκοπός αυτής της μελέτης είναι η καταχώρηση στη βιβλιογραφία νέων στοιχείων σχετικά με την επίδραση αυτών των εκδοχών και συνεπώς η διευκόλυνση κατά την επιλογή των καταλληλότερων συνδυασμών φορέων-εκδοχών στο σχεδιασμό επιθυμητών φαρμακοτεχνικών μορφών. / It is well known that liposomes offer many advantages for the delivery and/or targeting of drugs (Lasic 1993, Gregoriadis 1988). When mucosal or topical delivery of liposomal formulations is considered (Rollan 1993, Schreier and Bouwstra, 1994), it is essential that rheological and/or mucoadhesive properties of the liposome dispersions are adjusted accordingly, depending on the intended route of administration. This can be easily dome by adding gelling agents in the liposomal dispersions. Thereby, eventually a drug-in-liposome-in gel complex formulation is developed. Depending on the retention of the drug in the liposomes after the liposomes are dispersed in the preferred formulation, the release rate of the drug may be modified. This is highly related with two major groups of factors; • First the stability of the liposomes (membrane integrity and mechanical stability) during dispersion in the semi-solid formulation that may be related to the vesicle-membrane rigidity as well as the semisolid system physical properties (viscosity and rheological properties). • Second, the physicochemical properties of the drug formulated. A more lipophilic drug with low aqueous solubility should be logically retained for longer time periods in liposome lipid bilayers when compared with amphiphillic drugs with considerable high aqueous solubility (that will be the driving force to move drug molecules to partition in the aqueous environments until saturation occurs). In some cases, in addition to the gelling agents it is essential to have also other excipients in the complex drug-in-liposome-in-gel systems, as solubilizers, surfactants, co-surfactants et.c. Herein, we evaluate the effect of such excipients on the release of drugs from complex systems. We chose to use trancutol, propylene glycol, cremophor and labrafac-hydro, that are commonly used excipients in pharmaceutical formulations. In order to evaluate the extent to which these compounds can affect the release rate of drugs from drug-in-liposome-in-gel systems we followed the release of two model compounds, one hydrophilic dye (calcein) and one lipophilic drug (griseofulvin). The effect of the rigidity of liposomal membranes was evaluated by testing two different liposome lipid compositions for each case of encapsulated compounds, one that is known to be what is called “leaky”, which is the plain PC (egg lecithin) composition, and one which is very rigid, which is the DSPC/Chol (1:1 mol/mol) composition. Additionally, we also evaluated the effect of the gel composition and characteristics, by studying the release of both drugs from liposomes that have been dispersed in systems with different properties. For this we used gels composed of the acrylic acid based polymer Carbopol 974, which is a substance of many commercially available semisolid formulations, at two different concentrations (same rheological properties and different viscosity) as well as a cellulose based gel, composed of hydroxyethyl-cellulose (different rheological properties). Additionally we evaluated also a mixture of the two polymers, which has been proposed as a formulation base with several advantages, for vaginal delivery of drugs. In addition, we studied the stability of liposomes during incubation in the presence of the plain excipients (in 2 different concentrations, 10% and 25%) in order to see if this can be correlated on the effect of the same agents on drug release from the complex systems. The general conclusion extracted from the experimental results of this study is that the effect of the excipients on liposome stability depend on (i) the lipid composition of the liposomal membranes, (ii) the inclusion of cholesterol in the liposomes or not, (iii) the lipophilicity of the excipient and (iv) the concentration of the excipient. More analytically: In respect to liposome stability: 1. PC liposomes are easily disrupted with or without the presence of the excipients in the gels. 2. The very rigid DSPC/Chol (1:1 mol/mol) liposomes demonstrate higher stability. 3. In both cases the effect of the excipients follows the sequence: Transcutol ≈ Propylene-glycol < Cremophor < Labrafac. 4. Labrafac has the highest effect on liposome stability it practically dissolves liposomal membranes. 5. Cholesterol inclusion in liposomal membranes results in increased stability, however even the most stable DSPC/Chol (1:1) liposomes are very unstable in presence of Labrafac. In respect to the release of liposomal drugs from the complex systems in presence of the excipients studied: 3. A significant finding is that there is a difference in the release pattern and rate between lipophilic and hydrophilic liposome-encapsulated molecules, in the presence of excipient or not (control studies).. 4. In general, there seems to be a correlation between the stability of liposomes in presence of excipients and the effect that the specific excipient has on the release kinetics of liposome encapsulated molecules from complex drug-in-liposome-in-gel systems. 5. The release of lipophilic molecules (that are encapsulated in the lipospmes) from complex systems can be substantially sustained when lipophilic excipients are added in the gel (as is the case of griseofulvin and labrafac). Concluding, we stress the fact that the invention of new drug delivery systems with better performance is a great challenge for scientists involved in pharmaceutics. The systems studied here are offering many advantages due to their biocompatible nature and the extended number of applications they may have. The final scope of this study is the entry of new data about the effect of excipients on the properties of complex drug delivery systems. As the availability similar data in the related literature increases, it will become more easy to make the best selection of excipients during the development of better formulations for existing of new drugs.

Le travail réalisé concerne l’étude de la fonctionnalité et des performances des poudres de mannitol en compression directe en s’appuyant sur la simulation de compression sur presse rotative comme outil d’investigations. Dans le contexte réglementaire actuel, il est important pour les industriels, fournisseurs d’excipients pharmaceutiques, d’approfondir leurs connaissances des matériaux afin de répondre aux critères de qualité des médicaments et aux exigences de l’industrie pharmaceutique. Le mannitol est un excipient très largement utilisé en formulation pharmaceutique et notamment pour la conception de comprimés. L’objectif essentiel de cette Etude vise à mieux connaître et maîtriser la qualité de cette matière première afin de pouvoir améliorer, voire optimiser ses performances en compression directe. A l’aide d’une série de tests de caractérisation physiques, physico-chimiques, mécaniques et de compression sur les poudres de mannitol, nous avons pu identifier, dans un premier temps, un certain nombre de critères qui nous ont permis d’émettre des hypothèses et d’établir des axes de travail afin d’analyser le comportement de ces poudres en compression. Les résultats obtenus ont également permis de mettre en avant, à l’aide de l’étude de la compressibilité et des modèles mathématiques associés, un mécanisme de déformation prédominant sur les poudres de mannitol de compression directe. De nombreux prototypes ont fait l’objet d’une investigation approfondie dans une seconde partie, permettant de valider ces hypothèses et d’identifier les paramètres et mécanismes responsables des performances en compression des poudres de mannitol.Globalement, les travaux de recherche conduits dans cette thèse ont permis d’améliorer les connaissances sur les performances en compression des poudres de mannitol de la société Roquette Frères dans des conditions réelles d’utilisation, semblables aux presses rotatives industrielles, et en fournissant des résultats expérimentaux validés et modélisés. / This work focuses on the study of the functionality and performance of directly compressed mannitol powder using a rotary tablet press simulator as an investigation tool. For regulatory authority, it is essential for industrial - pharmaceutical raw material suppliers, to deepen their knowledge about materials to satisfy the drug quality standards and Pharmaceutical industry requirements. Mannitol is a widely used raw material in pharmaceutical formulations for the design of tablets. The main objective of this study is to have a better control and knowledge about this raw material quality, in order to improve and optimize the performance of mannitol in direct compression.Using a series of physical, physico-chemical, mechanical and compression studies on mannitol powders, we identified some criteria that allowed us to emit hypotheses and build a line of work to analyze the powders behavior under compression. The results also allowed us - using compressibility and associated mathematical models - to study the predominant deformation mechanism of directly compressed mannitol powders. Various mannitol prototypes were studied in a second part, permitting to validate these hypotheses and identify parameters and mechanisms affecting tableting performance.Overall, the research work achieved in this thesis have improved the knowledge about compression performance of mannitol powders from Roquette Frères SA company in tablet production used conditions, similar to industrial rotary tablet press, and providing validated and modeled experimental results.

Uma vacina liofilizada, em comparação a uma líquida, possui inúmeras vantagens, tais como: a melhora na estabilidade do produto às variações de temperatura aumentando sua vida de prateleira, possibilitando uma melhor logística do produto aos locais onde o acesso à rede refrigerada é difícil. O presente trabalho visou investigar as estratégias do processo para a conservação da potência da vacina rábica de uso veterinário por liofilização. O material testado foi a vacina rábica inativada (VRI). Ao total foram testados 13 excipientes com três concentrações diferentes. O processo de triagem utilizado para a escolha das melhores formulações (VRI + excipiente) foi liofilização em microplacas próprias para cultivo celular adaptadas ao liofilizador, sendo posteriormente verificada a preservação da antigenicidade da vacina por meio do teste de ELISA. A análise estatística foi realizada no programa SPSS® v.17, aplicando análise de regressão para dados categóricos. A arginina 0,5%, o PEG 3350 0,5%, a sacarose 2%, a maltose 1% e a trealose 1% foram os que deram melhores resultados, um alto \"score\" de antigenicidade em comparação à vacina liofilizada sem adição de excipientes. A temperatura de colapso da VRI e de suas diversas formulações foi determinada por meio de um microscópio acoplado a um módulo de liofilização. A análise térmica foi realizada em Calorimetria Exploratória Diferencial (Differential Scanning Calorimetry - DSC). Realizou-se os seguintes testes para avaliação da VRI liofilizada em frasco ampola: microscopia eletrônica de varredura (MEV) para análise da estrutura da pastilha e o antibody-binding test (ABT) - Teste de ligação do anticorpo modificado para determinação da potência da VRI e suas formulações. A umidade residual da VRI com PEG3350 0,5% liofilizada foi determinada em temperatura constante de 100ºC resultou em 1,60%. A pastilha da vacina rábica + PEG 3350 0,5% liofilizada em frasco ampola apresentou a elegância farmacêutica esperada de um produto liofilizado. / A lyophilized vaccine, compared to a liquid form, has many advantages, such as the improvement in product stability to changes in temperature by increasing its shelf life, allowing better logistics for product to locations where access to chill is difficult to achieve. This work has investigated the strategies of the process for the conservation of the potency of rabies vaccine for veterinary use by lyophilization. The material tested is an inactivated rabies vaccine (VRI). Altogether 13 excipients were tested with three different concentrations. The screening process used to choose best formulation (s) (VRI + excipient) was lyophilization in microplates suitable for cell culture adapted to the lyophilizer, and subsequently verified the preservation of the antigenicity of the vaccine through the ELISA test. Statistical analysis was performed using SPSS® v.17, applying regression analysis for categorical data. Arginine 0.5%, PEG 3350 0.5%, Sucrose 2%, Maltose 1% and Trehalose 1% were those that gave better results, a high score of antigenicity compared to the lyophilized vaccine with no added excipients. The temperature of collapse of VRI and its various formulations was determined using a microscope coupled to a module of lyophilization. Thermal analysis was performed in Differential Scanning Calorimetry (DSC). The following tests were used for evaluation of freeze-dried VRI: Scanning electron microscopy (SEM), Antibody-binding test (ABT). The residual moisture of lyophilized samples were determined in the moisture analyzer at constant temperature of 100 °C and resulted in 1.60%. The cake of lyophilized rabies vaccine + 0.5% PEG 3350 in vial showed the pharmaceutical elegance expected of a lyophilized product.

Uma vacina liofilizada, em comparação a uma líquida, possui inúmeras vantagens, tais como: a melhora na estabilidade do produto às variações de temperatura aumentando sua vida de prateleira, possibilitando uma melhor logística do produto aos locais onde o acesso à rede refrigerada é difícil. O presente trabalho visou investigar as estratégias do processo para a conservação da potência da vacina rábica de uso veterinário por liofilização. O material testado foi a vacina rábica inativada (VRI). Ao total foram testados 13 excipientes com três concentrações diferentes. O processo de triagem utilizado para a escolha das melhores formulações (VRI + excipiente) foi liofilização em microplacas próprias para cultivo celular adaptadas ao liofilizador, sendo posteriormente verificada a preservação da antigenicidade da vacina por meio do teste de ELISA. A análise estatística foi realizada no programa SPSS® v.17, aplicando análise de regressão para dados categóricos. A arginina 0,5%, o PEG 3350 0,5%, a sacarose 2%, a maltose 1% e a trealose 1% foram os que deram melhores resultados, um alto \"score\" de antigenicidade em comparação à vacina liofilizada sem adição de excipientes. A temperatura de colapso da VRI e de suas diversas formulações foi determinada por meio de um microscópio acoplado a um módulo de liofilização. A análise térmica foi realizada em Calorimetria Exploratória Diferencial (Differential Scanning Calorimetry - DSC). Realizou-se os seguintes testes para avaliação da VRI liofilizada em frasco ampola: microscopia eletrônica de varredura (MEV) para análise da estrutura da pastilha e o antibody-binding test (ABT) - Teste de ligação do anticorpo modificado para determinação da potência da VRI e suas formulações. A umidade residual da VRI com PEG3350 0,5% liofilizada foi determinada em temperatura constante de 100ºC resultou em 1,60%. A pastilha da vacina rábica + PEG 3350 0,5% liofilizada em frasco ampola apresentou a elegância farmacêutica esperada de um produto liofilizado. / A lyophilized vaccine, compared to a liquid form, has many advantages, such as the improvement in product stability to changes in temperature by increasing its shelf life, allowing better logistics for product to locations where access to chill is difficult to achieve. This work has investigated the strategies of the process for the conservation of the potency of rabies vaccine for veterinary use by lyophilization. The material tested is an inactivated rabies vaccine (VRI). Altogether 13 excipients were tested with three different concentrations. The screening process used to choose best formulation (s) (VRI + excipient) was lyophilization in microplates suitable for cell culture adapted to the lyophilizer, and subsequently verified the preservation of the antigenicity of the vaccine through the ELISA test. Statistical analysis was performed using SPSS® v.17, applying regression analysis for categorical data. Arginine 0.5%, PEG 3350 0.5%, Sucrose 2%, Maltose 1% and Trehalose 1% were those that gave better results, a high score of antigenicity compared to the lyophilized vaccine with no added excipients. The temperature of collapse of VRI and its various formulations was determined using a microscope coupled to a module of lyophilization. Thermal analysis was performed in Differential Scanning Calorimetry (DSC). The following tests were used for evaluation of freeze-dried VRI: Scanning electron microscopy (SEM), Antibody-binding test (ABT). The residual moisture of lyophilized samples were determined in the moisture analyzer at constant temperature of 100 °C and resulted in 1.60%. The cake of lyophilized rabies vaccine + 0.5% PEG 3350 in vial showed the pharmaceutical elegance expected of a lyophilized product.

Protein aggregation is a frequently cited problem during the development of liquid protein formulations, which is especially problematic since each protein exhibits different aggregation behaviour. Aggregation can be controlled by judicious choice of solution conditions, such as salt and buffer type and concentration, pH, and small molecule additives. However, finding conditions is still a trial and error process. In order to improve formulation development, a fundamental understanding of how excipients impact upon protein aggregation would significantly contribute to the development of stable protein therapeutics. The underlying mechanisms that control effects of excipients on protein behaviour are poorly understood. This dissertation is directed at understanding how excipients alter the conformational and colloidal stability of proteins and the link to aggregation. This knowledge can be used for finding novel ways of either predicting or preventing/inhibiting protein aggregation. Experiments using static and dynamic light scattering, intrinsic fluorescence, turbidity and electrophoretic light scattering were conducted to study the effect of solution conditions such as pH, salt type and concentration on protein aggregation behaviour for three model systems: lysozyme, insulin and a monoclonal antibody. Emphasis is placed on understanding the effects of solution additives on protein-protein interactions and the link to aggregation. This understanding has allowed the rational development of stable formulations with novel additives, such as arginine containing dipeptides and polycations.

Diss. (sammanfattning) Uppsala : Univ., 2002. / Härtill 5 uppsatser.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Metronidazole is a synthetic, nitroimidazole-derivative antibacterial and antiprotozoal agent (ed. McEvoy, 2001). It has been reported that crystallization occurs in aqueous suspensions of metronidazole benzoate, a bland-tasting prodrug of metronidazole, as a result of conversion from the anhydrous to the monohydrate form, thereby compromising the stability and clinical efficacy of the substance due to the particle size growth (Hoelgaard & Moller, 1983). A generic South African based pharmaceutical company commenced formulation of an aqueous metronidazole benzoate suspension and experienced problems with crystallization that occurred in products stored at 2 to 8 °C. This study aimed to continue development of the product in order to identify a formulation that prevents formation of the hydrate form of metronidazole benzoate and the accompanying crystal growth. A variety of metronidazole benzoate suspensions were manufactured on a laboratory scale using a number of natural and synthetic suspending agents, including magnesium aluminium silicate, povidone K90, xanthan gum and Avicel® RC-591 (microcrystalline cellulose and carboxymethylcellulose sodium), over a range of concentrations. Analytical quantification methods were developed and validated, and the physicochemical properties of the raw material and finished products were fully characterized. Rheological tests were performed in order to characterize the suspension flow properties. Real-time and accelerated stability studies and a temperature cycle study were conducted in accordance with the International Conference on Harmonization (ICH) guidelines. Conversion of metronidazole benzoate to the monohydrate form took place in suspensions containing xanthan gum 0.65 percent m/v under real-time and accelerated storage conditions. The suspensions containing Avicel® RC-591 were found to be physically and chemically stable after the temperature cycle and over the 12-week period whilst stored at 25 ºC / 60 percent RH and 5 ºC. The suspensions were chemically stable whilst stored at 40 ºC / 75 percent RH but showed sedimentation at this accelerated condition. The metronidazole benzoate contained in these products remained in the anhydrous state under all storage conditions and were consequently concluded to be the most stable formulations out of all the products analyzed in the current study. The suspending agent system consisting of microcrystalline cellulose and carboxymethylcellulose sodium thus shows promise in preventing the conversion of metronidazole benzoate from the anhydrate to the monohydrate form, thereby inhibited the subsequent increase in particle size due to crystal growth.