Investigations into the stabilisation of drugs by sugar glasses: I. Tablets prepared from stabilised alkaline phosphatase

Screening and Stability Evaluation of Freeze-Dried Protective Agents for a Live Recombinant Pseudorabies Virus Vaccine

Infection of pigs with the pseudorabies virus (PRV) causes significant economic losses in the pig industry. Immunization with live vaccines is a crucial aspect in the prevention of pseudorabies in swine. The TK/gE/gI/11k/28k deleted pseudorabies vaccine is a promising alternative for the eradication of epidemic pseudorabies mutant strains. This study optimized the lyophilization of a heat-resistant PRV vaccine to enhance the quality of a live vaccine against the recombinant PRV rHN1201TK-/gE-/gI-/11k-/28k-. The A4 freeze-dried protective formulation against PRV was developed by comparing the reduction in virus titer after lyophilization and after seven days of storage at 37 °C. The formulation contains 1% gelatin, 5% trehalose, 0.5% poly-vinylpyrimidine (PVP), 0.5% thiourea, and 1% sorbitol. The A4 freeze-dried vaccine demonstrated superior protection and thermal stability. It experienced a freeze-dried loss of 0.31 Lg post-freeze-drying and a heat loss of 0.42 Lg after being stored at a temperature of 37 °C for 7 consecutive days. The A4 freeze-dried vaccine was characterized through XRD, FTIR, and SEM analyses, which showed that it possessed an amorphous structure with a consistent porous interior. The trehalose component of the vaccine formed stable hydrogen bonds with the virus. Long-term and accelerated stability studies were also conducted. The A4 vaccine maintained viral titer losses of less than 1.0 Lg when exposed to 25 °C for 90 days, 37 °C for 28 days, and 45 °C for 7 days. The A4 vaccine had a titer loss of 0.3 Lg after storage at 2-8 °C for 24 months, and a predicted shelf life of 6.61 years at 2-8 °C using the Arrhenius equation. The A4 freeze-dried vaccine elicited no side effects when used to immunize piglets and produced specific antibodies. This study provides theoretical references and technical support to improve the thermal stability of recombinant PRV rHN1201TK-/gE-/gI-/11k-/28k- vaccines.

Tableting properties of freeze-dried trehalose: Physico-chemical and mechanical investigation

Freeze-drying of biopharmaceutical products is the method of choice in order to improve their stability and storage conditions. Such freeze-dried products are usually intended for parenteral route administration. However, many biopharmaceutical materials administered by parenteral route are used to treat local diseases particularly in the gastro-intestinal tract. Therefore, many studies concentrate nowadays their effort on developing alternative dosage forms to deliver biopharmaceutical molecules by the oral route. Tablets are the most popular solid pharmaceutical dosage form used for oral administration since they present many advantages, but poor informations are available on the possibility of tableting freeze-dried powders. In this study, we evaluate the compaction behavior of freeze-dried trehalose powder since trehalose is one of the most used cryo and lyoprotectant for the lyophilisation of biopharmaceutical entities. Results show that freeze-dried trehalose powder can be tableted while remaining amorphous and the obtained compacts present very specific properties in terms of compressibility, tabletability, brittleness and viscoelasticity compared to the crystalline trehalose and compared to classical pharmaceutical excipients.

The physiological functions and pharmaceutical applications of inulin: A review

Inulin (IN), a fructan-type plant polysaccharide, is widely found in nature. The major plant sources of IN include chicory, Jerusalem artichoke, dahlia etc. Studies have found that IN possessed a wide array of biological activities, e.g. as a prebiotic to improve the intestinal microbe environment, regulating blood sugar, regulating blood lipids, antioxidant, anticancer, immune regulation and so on. Currently, IN is widely used in the food and pharmaceutical industries. IN can be used as thickener, fat replacer, sweetener and water retaining agent in the food industry. IN also can be applied in the pharmaceutics as stabilizer, drug carrier, and auxiliary therapeutic agent for certain diseases such as constipation and diabetes. This paper reviews the physiological functions of IN and its applications in the field of pharmaceutics, analyzes its present research status and future research direction. This review will serve as a one-in-all resource for the researchers who are interested to work on IN.

Inhomogeneous Distribution of Components in Solid Protein Pharmaceuticals: Origins, Consequences, Analysis, and Resolutions

Successful development of stable solid protein formulations usually requires the addition of one or several excipients to achieve optimal stability. In these products, there is a potential risk of an inhomogeneous distribution of the various ingredients, specifically the ratio of protein and stabilizer may vary. Such inhomogeneity can be detrimental for stability but is mostly neglected in literature. In the past, it was challenging to analyze inhomogeneous component distribution, but recent advances in analytical techniques have revealed new options to investigate this phenomenon. This paper aims to review fundamental aspects of the inhomogeneous distribution of components of freeze-dried and spray-dried protein formulations. Four key topics will be presented and discussed, including the sources of component inhomogeneity, its consequences on protein stability, the analytical methods to reveal component inhomogeneity, and possible solutions to prevent or mitigate inhomogeneity.

Towards the Oral Treatment of Ileo-Colonic Inflammatory Bowel Disease with Infliximab Tablets: Development and Validation of the Production Process

Infliximab (IFX) is an intravenously administered monoclonal antibody antagonizing the effects of tumor necrosis factor-alpha (TNF) systemically and is efficacious in the treatment of inflammatory bowel disease (IBD). However, studies suggest that the anti-inflammatory effects result from local immunomodulation in the inflamed regions. Furthermore, topical inhibition of TNF in IBD ameliorates inflammation. We therefore hypothesized that orally administered IFX targeted to the ileo-colonic region in IBD may be an efficacious new treatment option. This study describes the development and validation of the production process of ileo-colonic-targeted 5 mg IFX tablets (ColoPulse-IFX) intended for the oral treatment of IBD by means of producing three consecutive validation batches (VAL1, VAL2, and VAL3, respectively). UV-VIS spectroscopy, HPLC-SEC analysis (content, fragments, aggregates), fluorescence spectroscopy (tertiary protein structure), and ELISA (potency) showed no noticeable deviations of IFX compounded to ColoPulse-IFX compared to fresh IFX stock. The average ± SD (n = 10) IFX content of VAL1, VAL2, and VAL3 was 96 ± 2%, 97 ± 3%, and 96 ± 2%, respectively, and complied with the European Pharmacopeia (Ph. Eur.) requirements for Content Uniformity. The average ± SD (n = 3) ColoPulse-IFX potency was 105 ± 4%, 96 ± 4%, and 97 ± 5%, respectively, compared to fresh IFX stock. The IFX release profile from the tablet core was complete (≥85%) after 10 min in simulated ileum medium. The in vitro coating performance of ColoPulse-IFX showed that the formulation was targeted to the simulated ileo-colonic region. Stability data showed that ColoPulse-IFX was stable for up to 6 months stored at 25 °C/60% RH. Based on these results, the production process can be considered validated and its application is discussed in light of the rationale and available evidence for the topical treatment of IBD with IFX.

A novel method for studying airway hyperresponsiveness in allergic guinea pigs in vivo using the PreciseInhale system for delivery of dry powder aerosols

Inhaled adenosine receptor agonists induce bronchoconstriction and inflammation in asthma and are used as bronchial challenge agents for the diagnosis of asthma and in respiratory drug development. Recently developed dry powder aerosols of adenosine have several advantages over nebulised adenosine 5′-monophosphate (AMP) as bronchial challenge agents. However, reverse translation of this bronchial challenge technique to pre-clinical drug development is limited by the difficulty of administering powder aerosols to animals. The aim of the current study was to develop methods for delivering powder aerosols of adenosine receptor agonists to sensitised guinea pigs (as a model of allergic asthma) and evaluate their effect as challenge agents for the measurement of airway responsiveness. The PreciseInhale system delivered micronised AMP and adenosine powders, with mass median aerodynamic diameters of 1.81 and 3.21 μm and deposition fractions of 31 and 48% in the lungs, respectively. Bronchoconstrictor responses in passively sensitised, anaesthetised, spontaneously breathing guinea pigs were compared to responses to nebulised and intravenously administered AMP and adenosine. AMP- and adenosine-induced bronchoconstriction following all routes of administration with the magnitude of response ranking intravenous > dry powder > nebulisation, probably reflecting differences in exposure to the adenosine agonists delivered by the different routes. In conclusion, the PreciseInhale system delivered AMP and adenosine dry powder aerosols accurately into the lungs, suggesting this method can be used to investigate drug effects on airway responsiveness.

Stabilization of luteinizing hormone-releasing hormone in a dry powder formulation and its bioactivity

Background: Luteinizing hormone-releasing hormone (LHRH) is a naturally occurring hormone that controls sex hormones in both men and women. In general, LHRH is poorly absorbed through the gastrointestinal tract due to its large molecular size, high polarity, and loss from enzymatic degradation.

Objective: Prepare and develop LHRH in a dry power formulation with stability and biological activity.

Methods: Mannitol (M) and glycine (G) were chosen as ingredients to stabilize and protect LHRH during the freeze drying processes and during storage. The physicochemical properties of LHRH dry powders were examined by capillary electrophoresis, fluorescence spectrophotometry, scanning electron microscopy, and photon correlation spectroscopy. The release of LHRH from the dry powder was carried out in dissolution apparatus. In addition, a rat model was employed to study the bioactivity of LHRH in the dry powder form.

Results: The LHRH dry powder formulations using M and G in the ratios of 6:4 and 7:3 were more stable than other formulations. LHRH colloids containing M:G showed no aggregation after storage at 4°C for one month. The concentration of LHRH in the dry powder form was more stable than that of LHRH in solution form. All the LHRH dry powder formulations were instantly dissolved within 10 seconds in an aqueous medium. After the LHRH dry powder (13 mg) was reconstituted and administered intraperitoneally to male rats during a one-month period, the testosterone level in the plasma was significantly decreased compared with an untreated group (15.0±1.0 ng/mL, 15.0±1.0 ng/mL and 20.0±2.0 ng/mL for LHRH containing M:G; 6:4, 7:3, and 8:2, respectively, compared to the control of 35±2 ng/mL, p<0.05).

Conclusion: The LHRH dry powder formulations had good physicochemical properties and bioactivity.

Structural and functional stabilization of protein entities: state-of-the-art

Within the context of biomedicine and pharmaceutical sciences, the issue of (therapeutic) protein stabilization assumes particular relevance. Stabilization of protein and protein-like molecules translates into preservation of both structure and functionality during storage and/or targeting, and such stabilization is mostly attained through establishment of a thermodynamic equilibrium with the (micro)environment. The basic thermodynamic principles that govern protein structural transitions and the interactions of the protein molecule with its (micro)environment are, therefore, tackled in a systematic fashion. Highlights are given to the major classes of (bio)therapeutic molecules, viz. enzymes, recombinant proteins, (macro)peptides, (monoclonal) antibodies and bacteriophages. Modification of the microenvironment of the biomolecule via multipoint covalent attachment onto a solid surface followed by hydrophilic polymer co-immobilization, or physical containment within nanocarriers, are some of the (latest) strategies discussed aiming at full structural and functional stabilization of said biomolecules.

The effect of thermal treatment of radiation-induced EPR signals of different polymorphic forms of trehalose

Electron paramagnetic resonance (EPR) signals induced by γ-radiation in different polymorphic forms of trehalose were studied with dosimetry applications in view. Dose response of trehalose in terms of the concentration of induced paramagnetic centers was studied in the dose range from 0.5 to 50 kGy. The dependences of the dose responses of anhydrous β-crystalline trehalose (TRE(β)) and glassy trehalose (TRE(g)) on dose are linear up to 15 kGy, whereas the linearity of the dependence for trehalose dihydrate (TRE(h)) is limited to about 10 kGy. At doses above 15 kGy, the dependences get saturated for all three forms. The relative radiation sensitivities pointed to the following order of decreasing concentrations of radiation-induced paramagnetic centers in the forms: TRE(g)>TRE(β)>TRE(h). The results showed that at all three trehalose polymorphic forms are suitable for dosimetry, especially for retrospective dose measurements. Also, thermal stability and decay kinetics of the EPR signals of the different forms of trehalose were studied in isothermal annealing experiments. The kinetic parameters, which had been derived by fitting the Arrhenius function to the measured decay rate constants, indicated that the fading of the EPR signals varied from one polymorphic form of trehalose to another. This emphasizes the impact of the molecular packing in the vicinity of the radiation-induced paramagnetic centers on their stability.

Development of stable influenza vaccine powder formulations: challenges and possibilities

Influenza vaccination represents the cornerstone of influenza prevention. However, today all influenza vaccines are formulated as liquids that are unstable at ambient temperatures and have to be stored and distributed under refrigeration. In order to stabilize influenza vaccines, they can be brought into the dry state using suitable excipients, stabilizers and drying processes. The resulting stable influenza vaccine powder is independent of cold-chain facilities. This can be attractive for the integration of the vaccine logistics with general drug distribution in Western as well as developing countries. In addition, a stockpile of stable vaccine formulations of potential vaccines against pandemic viruses can provide an immediate availability and simple distribution of vaccine in a pandemic outbreak. Finally, in the development of new needle-free dosage forms, dry and stable influenza vaccine powder formulations can facilitate new or improved targeting strategies for the vaccine compound. This review represents the current status of dry stable inactivated influenza vaccine development. Attention is given to the different influenza vaccine types (i.e. whole inactivated virus, split, subunit or virosomal vaccine), the rationale and need for stabilized influenza vaccines, drying methods by which influenza vaccines can be stabilized (i.e. lyophilization, spray drying, spray-freeze drying, vacuum drying or supercritical fluid drying), the current status of dry influenza vaccine development and the challenges for ultimate market introduction of a stable and effective dry-powder influenza vaccine.

Inulin sugar glasses preserve the structural integrity and biological activity of influenza virosomes during freeze-drying and storage

Influenza virosomes are reconstituted influenza virus envelopes that may be used as vaccines or as carrier systems for cellular delivery of therapeutic molecules. Here we present a procedure to generate influenza virosomes as a stable dry-powder formulation by freeze-drying (lyophilization) using an amorphous inulin matrix as a stabilizer. In the presence of inulin the structural integrity and fusogenic activity of virosomes were fully preserved during freeze-drying. For example, the immunological properties of the virosomes, i.e. the HA potency in vitro and the immunogenic potential in vivo, were maintained during lyophilization in the presence of inulin. In addition, compared to virosomes dispersed in buffer, inulin-formulated virosomes showed substantially prolonged preservation of the HA potency upon storage. Also the capacity of virosomes to mediate cellular delivery of macromolecules was maintained during lyophilization in the presence of inulin and upon subsequent storage. Specifically, when dispersed in buffer, virosomes with encapsulated plasmid DNA lost their transfection activity completely within 6 weeks, whereas their transfection activity was fully preserved for at least 12 weeks after incorporation in an inulin matrix. Thus, in the presence of inulin as a stabilizing agent, the shelf-life of influenza virosomes with and without encapsulated macromolecules was considerably prolonged. Formulation of influenza virosomes as a dry-powder is advantageous for storage and transport and offers the possibility to develop needle-free dosage forms, e.g. for oral, nasal, pulmonal, or dermal delivery.

Rational design of an influenza subunit vaccine powder with sugar glass technology: Preventing conformational changes of haemagglutinin during freezing and freeze-drying

The development of a stable influenza subunit vaccine in the dry state was investigated. The influence of various carbohydrates, buffer types and freezing rates on the integrity of haemagglutinin after freeze-thawing or freeze-drying was investigated with a range of analytical and immunological methods. The use of fast freezing, Hepes buffer and carbohydrates (trehalose, inulin or dextran) as cryo- and lyoprotectants resulted in a significant reduction or even absence of conformational changes of HA as revealed by the used methods. The subunit vaccine in the powder was shown to remain immunogenic in an in vivo study in mice, using reconstituted powder. Moreover, the HA potency of the influenza subunit vaccine powder was stable for at least 26 weeks at room temperature.

Polyionic hydrocolloids for the intestinal delivery of protein drugs: alginate and chitosan--a review

The protein pharmaceutical market is rapidly growing, since it is gaining support from the recombinant DNA technology. To deliver these drugs via the oral route, the most preferred route, is the toughest challenge. In the design of oral delivery of peptide or protein drugs, pH sensitive hydrogels like alginate and chitosan have attracted increasing attention, since most of the synthetic polymers are immunogenic and the incorporation of proteins in to these polymers require harsh environment which may denature and inactivate the desired protein. Alginate is a water-soluble linear polysaccharide composed of alternating blocks of 1-4 linked alpha-L-guluronic and beta-D-mannuronic acid residues where as chitosan is a co polymer of D-glucosamine and N-acetyl glucosamine. The incorporation of protein into these two matrices can be done under relatively mild environment and hence the chances of protein denaturation are minimal. The limitations of these polymers, like drug leaching during preparation can be overcome by different techniques which increase their encapsulation efficiency. Alginate, being an anionic polymer with carboxyl end groups, is a good mucoadhesive agent. The pore size of alginate gel microbeads has been shown to be between 5 and 200 nm and coated beads and microspheres are found to be better oral delivery vehicles. Cross-linked alginate has more capacity to retain the entrapped drugs and mixing of alginate with other polymers such as neutral gums, pectin, chitosan, and eudragit have been found to solve the problem of drug leaching. Chitosan has only limited ability for controlling the release of encapsulated compound due to its hydrophilic nature and easy solubility in acidic medium. By simple covalent modifications of the polymer, its physicochemical properties can be changed and can be made suitable for the peroral drug delivery purpose. Ionic interactions between positively charged amino groups in chitosan and the negatively charged mucus gel layer make it mucoadhesive. The favourable properties like biocompatibility, biodegradability, pH sensitiveness, mucoadhesiveness, etc. has enabled these polymers to become the choice of the pharmacologists as oral delivery matrices for proteins.

Spray freeze drying to produce a stable Δ9-tetrahydrocannabinol containing inulin-based solid dispersion powder suitable for inhalation

The purpose of this study is to investigate whether spray freeze drying produces an inhalable solid dispersion powder in which Delta(9)-tetrahydrocannabinol (THC) is stabilised. Solutions of THC and inulin in a mixture of tertiary butanol (TBA) and water were spray freeze dried. Drug loads varied from 4 to 30 wt.%. Various powder characteristics of the materials were determined. Stability of THC was determined and compared with freeze dried material. The powders, dispersed with an inhaler based on air classifier technology, were subjected to laser diffraction analysis and cascade impactor analysis. Highly porous particles having large specific surface areas (about 90 m(2)/g) were produced. At high drug loads, THC was more effectively stabilised by spray freeze drying than by freeze drying. Higher cooling rates during spray freeze drying result in improved incorporation. Fine particle fractions of up to 50% were generated indicating suitability for inhalation. It was concluded that spray freeze drying from a water-TBA mixture is a suitable process to include lipophilic drugs (THC) in inulin glass matrices. High cooling rates during the freezing process result in effective stabilisation of THC. The powders can be dispersed into aerosols with a particle size appropriate for inhalation.

Inulin is a promising cryo- and lyoprotectant for PEGylated lipoplexes

The aim of this study was to investigate whether the oligosaccharides dextran and inulin are able to prevent aggregation of lipoplexes based on 1,2-dioleoyl-3-trimethylammonium-propane and dioleoylphosphatidyl-ethanolamine with and without distearoylphosphatidylethanolamine-polyethyleneglycol (PEGylated and nonPEGylated lipoplexes, respectively) during storage. The lipoplexes, dispersed in the oligosaccharide solution were frozen and subsequently stored at subzero temperature or freeze dried and subsequently stored at 37 degrees C. When lipoplexes in frozen dispersions were stored below the glass transition temperature of the maximally freeze concentrated fraction (Tg') of the oligosaccharide solutions severe aggregation of the nonPEGylated lipoplexes was prevented for 3 months by both inulin and dextran. However, while dextran failed to stabilize the frozen PEGylated lipoplexes (as in most cases full aggregation occurred in short time) inulin successfully protected them against aggregation. Compared to dextran, inulin was also a superior lyoprotectant of PEGylated lipoplexes: during freeze drying and subsequent storage at 37 degrees C of the dried powders for 3 months the PEGylated lipoplexes maintained their original size when dispersed in inulin matrices while in dextran matrices they fully aggregated in most cases. It is hypothesized that the aggregation of the PEGylated lipoplexes in dextran solutions is caused by the well known incompatibility between dextrans and PEG. This is further supported by the observation that inulins and PEG are compatible. It is concluded that oligosaccharides can prevent severe aggregation of nonPEGylated lipoplexes. The same holds for PEGylated lipoplexes provided that the oligosaccharide is compatible with PEG. Finally, this work also shows that the higher Tg' of oligosaccharides makes them more versatile cryoprotectants than disaccharides like sucrose or trehalose as the frozen dispersions can be stored at higher temperatures for prolonged periods of time. Furthermore, it is proposed that oligosaccharides are also more versatile lyoprotectants than the disaccharides because they can be exposed to higher relative humidities without passing the glass transition temperature.

Investigations into the stabilization of drugs by sugar glasses: III. The influence of various high-pH buffers

PURPOSE

To study the effect of the high-pH buffers ammediol, borax, CHES, TRIS, and Tricine on the glass transition temperature of the freeze concentrated fraction (Tg') of trehalose/buffer and inulin/buffer solutions at pH 6.0 and pH 9.8. Also, the glass transition temperature (Tg) of sugar glasses obtained after freeze drying of these solutions was elucidated. Additionally, the effect occurring during the freezing process on the pH of the various buffers was investigated. Furthermore, the stability of alkaline phosphatase (AP) incorporated in these sugar glasses prepared from solutions at pH 9.8 was evaluated.

METHODS

The Tg' and Tg were measured using differential scanning calorimetry (DSC), and the change of pH during freezing was estimated by using an indicator solution added to the respective solutions. The enzymatic activity of AP after freeze drying and storage at 60 degrees C was evaluated by an enzymatic activity assay.

RESULTS

It was found that the Tg' and Tg of the samples investigated are strongly influenced by the presence of the buffer. On freezing, only minor changes of the pH were observed. The samples with the lowest Tg and the samples containing buffers that formed complexes with the sugars showed the poorest stability of the AP.

CONCLUSIONS

The stabilizing capacities of sugars that are currently recognized as excellent stabilizers for proteins during drying and storage can be completely lost if certain high-pH buffers such as ammediol, borax, and TRIS are used at high concentrations. Loss of stabilizing capacities can be ascribed to strong depression of the Tg' and Tg or to complex formation.

Anomalous dissolution behaviour of tablets prepared from sugar glass-based solid dispersions

In this study, anomalous dissolution behaviour of tablets consisting of sugar glass dispersions was investigated. The poorly aqueous soluble diazepam was used as a lipophilic model drug. The release of diazepam and sugar carrier was determined to study the mechanisms governing dissolution behaviour. The effect of carrier dissolution rate and drug load was tested with four different sugars, in the order of decreasing dissolution rates: sucrose, trehalose and two oligo-fructoses; inulinDP11 and inulinDP23 having a number average degree of polymerization (DP) of 11 and 23, respectively. Diazepam was incorporated in these sugar glasses in the amorphous state by means of freeze drying using water and tertiary butyl alcohol (TBA) as solvents. None of the tablets disintegrated during dissolution. Dissolution of 80% of the lipophilic drug within 20 min was found when diazepam and sugar dissolution profiles coincided. The sugar carrier and diazepam dissolved at the same rate, which was constant in time and fast. This condition was met for relatively slow dissolving carriers like the inulins or for low drug loads. For relatively fast dissolving carriers like sucrose or trehalose with high drug loads, release profiles of diazepam and sugar did not coincide: diazepam dissolved much more slowly than the sugars. In case of non-coinciding release profiles, diazepam release was split into three phases. During the first phase non-steady-state dissolution was observed: diazepam release accelerated and a drug rich layer consisting of crystalline diazepam was gradually formed. This first phase determined the further release of diazepam. During the second phase a steady-state release rate was reached: zero-order release was observed for both drug and carrier. During this phase, the remaining (non-crystallised) solid dispersion is dissolved without the further occurrence of crystallisation. The third phase, starting when all carrier is dissolved, involved the very slow dissolution of crystallised diazepam, which was present either as the skeleton of a tablet resulting in a zero-order release profile or as separate particles dispersed in the dissolution medium resulting in a first-order release. To understand the anomalous dissolution behaviour, a model is proposed. It describes the phenomena during dissolution of amorphous solid dispersion tablets and explains that fast dissolution is observed for low drug loads or slow dissolving carriers like inulin.

Incorporation of Lipophilic Drugs in Sugar Glasses by Lyophilization using a Mixture of Water and Tertiary Butyl Alcohol as Solvent

In this study, a new and robust method was evaluated to prepare physically stable solid dispersions. Trehalose, sucrose, and two inulins having different chain lengths were used as carrier. Diazepam, nifedipine, Delta(9)-tetrahydrocannabinol, and cyclosporine A were used as model drugs. The sugar was dissolved in water and the drug in tertiary butyl alcohol (TBA). The two solutions were mixed in a 4/6 TBA/water volume ratio and subsequently freeze dried. Diazepam could be incorporated at drug loads up to 63% w/w. DSC measurements showed that, except in some sucrose dispersions, 97-100% of the diazepam was amorphous. In sucrose dispersions with high drug loads, about 10% of the diazepam had crystallised. After 60 days of exposure at 20 degrees C and 45% relative humidity (RH), diazepam remained fully amorphous in inulin dispersions, whereas in trehalose and sucrose crystallization of diazepam occurred. The excellent physical stability of inulin containing solid dispersions can be attributed to the high glass transition temperature (T(g)) of inulin. For the other drugs similar results were obtained. The residual amount of the low toxic TBA was only 0.1-0.5% w/w after freeze drying and exposure to 45% RH and 20 degrees C. Therefore, residual TBA will not cause any toxicity problems. This study provides a versatile technique, to produce solid dispersions. Inulin glasses are preferred because they provide an excellent physical stability of the incorporated amorphous lipophilic drugs.

Investigations into the stabilisation of drugs by sugar glasses: II. Delivery of an inulin-stabilised alkaline phosphatase in the intestinal lumen via the oral route

In this study the possibility to deliver the acid-sensitive enzyme alkaline phosphatase (AP) from calf intestine (CIAP) to the intestinal system by oral administration was investigated. Tablets were prepared and in vitro evaluated. Final proof of concept studies were performed in rats. This acid labile enzyme is potentially useful in the treatment of sepsis, a serious condition during which endotoxins can migrate into the blood stream. The CIAP was freeze-dried with inulin and subsequently compacted into round biconvex tablets with a diameter of 4mm and a weight of 25-30 mg per tablet. The tablets were coated with an enteric coating in order to ensure their survival in the stomach. In vitro evaluation of tablets containing alkaline phosphatase from bovine intestine (BIAP) was the first step in the development. It was found that tablets without enteric coating dissolved rapidly in 0.10 M HCl with total loss of enzymatic activity of the alkaline phosphatase. Tablets that were coated were stable for at least 2 h in 0.10 M HCl, but dissolved rapidly when the pH was increased to 6.8. Furthermore, it was shown that the enzymatic activity of the released BIAP was fully preserved. The in vivo test clearly showed that the oral administration of enteric coated tablets resulted in the release of enzymatically active CIAP in the intestinal lumen of rats. The location of the enhanced enzymatic activity of AP in the intestines varied with the time that had passed between the administration of the tablets and the sacrificing of the rats. Also, the level of enzymatic activity increased with an increasing number of tablets that were administered.