Study of dissolution hydrodynamic conditions versus drug release from hypromellose matrices: The influence of agitation sequence

Increasing the Dissolution Rate of Polystyrene Waste in Solvent-Based Recycling

Solvent-based recycling of plastic waste is a promising approach for cleaning polymer chains without breaking them. However, the time required to actually dissolve the polymer in a lab environment can take hours. Different factors play a role in polymer dissolution, including temperature, turbulence, and solvent properties. This work provides insights into bottlenecks and opportunities to increase the dissolution rate of polystyrene in solvents. The paper starts with a broad solvent screening in which the dissolution times are compared. Based on the experimental results, a multiple regression model is constructed, which shows that within several solvent properties, the viscosity of the solvent is the major contributor to the dissolution time, followed by the hydrogen, polar, and dispersion bonding (solubility) parameters. These results also indicate that cyclohexene, 2-pentanone, ethylbenzene, and methyl ethyl ketone are solvents that allow fast dissolution. Next, the dissolution kinetics of polystyrene in cyclohexene in a lab-scale reactor and a baffled reactor are investigated. The effects of temperature, particle size, impeller speed, and impeller type were studied. The results show that increased turbulence in a baffled reactor can decrease the dissolution time from 40 to 7 min compared to a lab-scale reactor, indicating the importance of a proper reactor design. The application of a first-order kinetic model confirms that dissolution in a baffled reactor is at least 5-fold faster than that in a lab-scale reactor. Finally, the dissolution kinetics of a real waste sample reveal that, in optimized conditions, full dissolution occurs after 5 min.

Effect of pH, Ionic Strength and Agitation Rate on Dissolution Behaviour of 3D-Printed Tablets, Tablets Prepared from Ground Hot-Melt Extruded Filaments and Physical Mixtures

With the current focus on 3D-printing technologies, it is essential to understand the processes involved in such printing methods and approaches to minimize the variability in dissolution behaviour to achieve better quality control outcomes. For this purpose, two formulations of theophylline tablets were prepared using hydroxypropyl cellulose (HPC) and ethyl cellulose (EC). Among the two types of tablets, three different methods (physical mixture (PM), hot-melt extrusion (HME) and 3D-printing fused deposition modelling (FDM)) were applied and their dissolution behaviours were studied under various conditions using a biodissolution tester. This was carried out at pH values of 1.2, 2.2, 5.8, 6.8, 7.2 and 7.5, mimicking the medium in the gastrointestinal tract. Dissolution tests under two dipping rates (10 dpm and 20 dpm) and two ionic strengths (0.2 M and 0.4 M) were conducted to mimic fed and fasting conditions. The dissolution efficiency (DE%), release rate, similarity factor (f₂) and difference factor (f₁) were calculated. When comparing the DE%, the formulation containing EC showed less sensitivity to changes in the dipping rate and ionic strength compared to the HPC formulation. As for the manufacturing method, 3D-printing FDM could improve the robustness of the dissolution behaviour of both formulations to dipping rate changes. However, for ionic strength changes, the effect of the manufacturing method was dependent on the formulation composition. For example, the 3D-printed tablets of the HPC formulation were more sensitive to changes in ionic strength compared to the EC-containing formulation. The release mechanism also changed after the thermal process, where n values in the Korsmeyer-Peppas model were much higher in the printing and HME methods compared to the PM. Based on the formulation composition, the 3D-printing method could be a good candidate method for tablets with a robust dissolution behaviour in the GI tract. Compared to HPC polymers, using hydrophobic EC polymers in printable formulations can result in a more robust dissolution behaviour in fed and fasting states.

Drug release from magnesium aluminium silicate-polyethylene oxide (PEO) nanocomposite matrices: An investigation using the USP III apparatus

This work investigated the use of the USP III apparatus in discriminating simulated fed and fasted conditions as well as ionic strength on veegum-polyethylene (PEO) (called clay-PEO matrices hereafter) matrices. The successful formulations were characterised using differential scanning calorimetry (DSC) and evaluated for their physical properties. Isothermal calorimetry (ITC) was used to evaluate the thermodynamics of the complexation processes. The effect of agitation sequences on the matrices as evaluated from the USP III suggested an increase in polymer content to significantly decrease the burst release experienced using diltiazem hydrochloride (DILT) as a model cationic drug. The manufacturing methods showed superior performance in relation to a decrease in burst release over the physical manufactured counterparts. The clay-PEO matrices also showed robustness (no matrix failure) in up to 0.2 M ionic strength solutions mimicking the upper limit experienced in the GI tract. ITC results revealed that the binding between DILT and PEO was enthalpy and entropy-driven. Furthermore, the binding between veegum and DILT in the presence of PEO was shown to be enthalpy-driven and entropically unfavourable, which was also the case for the binding between veegum and PEO thus giving insights to how the matrices were performing on a molecular level.

Exploring the Potential of Hydrophilic Matrix Combined with Insoluble Film Coating: Preparation and Evaluation of Ambroxol Hydrochloride Extended Release Tablets

To explore the potential utility of combination of hydrophilic matrix with membrane-controlled technology, the present study prepared tablets of a water-soluble model drug (ambroxol hydrochloride), through process of direct compression and spray coating. Single-factor experiments were accomplished to optimize the formulation. In vivo pharmacokinetics was then performed to evaluate the necessity and feasibility of further development of this simple process and low-cost approach. Various release rates could be easily obtained by adjusting the viscosity and amount of hypromellose, pore-former ratios in coating dispersions and coating weight gains. Dissolution profiles of coated tablets displayed initial delay, followed by near zero-order kinetics. The pharmacokinetic study of different formulations showed that lag time became longer as the permeability of coating membrane decreased, which was consistent with the in vitro drug release trend. Besides, in vitro/in vivo correlation study indicated that coated tablets exhibited a good correlation between in vitro release and in vivo absorption. The results, therefore, demonstrated that barrier-membrane-coated matrix formulations were extremely promising for further application in industrialization and commercialization.

Mechanical and release behaviour of theophylline from matrix tablets containing psyllium powder in combination with grewia polysaccharides

This study was aimed at investigating the effect of grewia polysaccharides on the mechanical and release properties of tablet matrices containing binary mixtures of the polysaccharide with psyllium. Two grades of grewia polysaccharides (GG and GDS) were extracted and binary mixtures of the polysaccharides with psyllium were formulated into tablet matrices containing theophylline as the model drug. The true, bulk and tapped densities, Carr's compressibility index of the powders and binary composites were determined before tablet compression. Tablet properties (hardness, porosity, and drug release from the matrices) were investigated. The dissolution test was carried out in 0.1 M HCl (pH 1.2) and phosphate buffer (pH 6.8). The results show that GG and GDS produced tablets with good mechanical strength (108.33 N and 95.70 N, respectively) while psyllium produced softer tablets (7.13 N). The combination of psyllium and grewia polysaccharides in the matrices resulted in a significant increase in the mechanical strength of the matrices when compared to matrices containing psyllium alone as the matrix former. The results also showed that GG and GDS reduced the dissolution rate and effectively eliminated the burst release of theophylline from the psyllium matrices at both pHs. The matrices of GG or GDS and the binary mixtures conform to non-Fickian anomalous diffusion with n > 0.45. When overcoming the burst release of drug from matrices such as psyllium, grewia polysaccharides may provide an effective reduction and a more sustained drug release from such matrices.

The influence of hydroalcoholic media on the performance of Grewia polysaccharide in sustained release tablets

Co-administration of drugs with alcohol can affect the plasma concentration of drugs in patients. It is also known that the excipients used in the formulation of drugs may not always be resistant to alcohol. This study evaluates effect of varying alcohol concentrations on theophylline release from two grades of Grewia mollis polysaccharides. X-ray microtomography showed that native polysaccharide formulation compacts were not homogenous after the mixing process resulting in its failure in swelling studies. Removal of starch from the native polysaccharide resulted in homogenous formulation compacts resistant to damage in high alcoholic media in pH 6.8 (40%v/v absolute ethanol). Destarched polymer compacts had a significantly higher hardness (375N) than that of the native polysaccharide (82N) and HPMC K4M (146N). Dissolution studies showed similarity at all levels of alcohol tested (f₂=57-91) in simulated gastric media (pH 1.2). The dissolution profiles in the simulated intestinal fluids were also similar (f₂=60-94), with the exception of the native polysaccharide in pH 6.8 (40%v/v absolute ethanol) (f₂=43). This work highlights the properties of Grewia polysaccharide as a matrix former that can resist high alcoholic effects therefore; it may be suitable as an alternative to some of the commercially available matrix formers with wider applications for drug delivery as a cheaper alternative in the developing world.

Correlation between the viscoelastic properties of the gel layer of swollen HPMC matrix tablets and their in vitro drug release

Drug release from hydroxypropyl methylcellulose (HPMC) hydrophilic matrix tablets is controlled by drug diffusion through the gel layer of the matrix-forming polymer upon hydration, matrix erosion or combination of diffusion and erosion mechanisms. In this study, the relationship between viscoelastic properties of the gel layer of swollen intact matrix tablets and drug release was investigated. Two sets of quetiapine fumarate (QF) matrix tablets were prepared using the high viscosity grade HPMC K4M at low (70 mg/tablet) and high (170 mg/tablet) polymer concentrations. Viscoelastic studies using a controlled stress rheometer were performed on swollen matrices following hydration in the dissolution medium for predetermined time intervals. The gel layer of swollen tablets exhibited predominantly elastic behavior. Results from the in vitro release study showed that drug release was strongly influenced by the viscoelastic properties of the gel layer of K4M tablets, which was further corroborated by results from water uptake studies conducted on intact tablets. The results provide evidence that the viscoelastic properties of the gel layer can be exploited to guide the selection of an appropriate matrix-forming polymer, to better understand the rate of drug release from matrix tablets in vitro and to develop hydrophilic controlled-release formulations.

An Investigation on the Effect of Polyethylene Oxide Concentration and Particle Size in Modulating Theophylline Release from Tablet Matrices

Polyethylene oxide has been researched extensively as an alternative polymer to hydroxypropyl methylcellulose (HPMC) in controlled drug delivery due to its desirable swelling properties and its availability in a number of different viscosity grades. Previous studies on HPMC have pointed out the importance of particle size on drug release, but as of yet, no studies have investigated the effect of particle size of polyethylene oxide (polyox) on drug release. The present study explored the relationship between polymer level and particle size to sustain the drug release. Tablets produced contained theophylline as their active ingredient and consisted of different polyethylene oxide particle size fractions (20-45, 45-90, 90-180 and 180-425 μm). It was shown that matrices containing smaller particle sizes of polyox produced harder tablets than when larger polyox particles were used. The release studies showed that matrices consisting of large polyox particles showed a faster release rate than matrices made from smaller particles. Molecular weight (MW) of the polymer was a key determining step in attaining sustained release, with the high MW of polyox resulting in a delayed release profile. The results showed that the effect of particle size on drug release was more detrimental when a low concentration of polyox was used. This indicates that care must be taken when low levels of polyox with different particle size fractions are used. More robust formulations could be obtained when the concentration of polyox is high. Differential scanning calorimetry (DSC) traces showed that particle size had no major effect on the thermal behaviour of polyox particles.

Applications of USP apparatus 3 in assessing the in vitro release of solid oral dosage forms

<p>USP Apparatus 3 (reciprocating cylinder) is a very versatile device for the <italic>in vitro</italic> assessment of release characteristics of solid oral dosage forms, because it enables the product to be subjected to different dissolution media and agitation speeds in a single run. In this paper, a brief history and a description of this system are presented, along with its applications in the development of immediate and modified release products and in the simulation of fasted and fed states using biorelevant media. Furthermore, a comparison is made with the basket and paddle apparatus, especially highlighting the superior hydrodynamics of USP apparatus 3, since the results are not sensitive to factors such as the presence of sample collection probes or air bubbles in the dissolution medium.</p>

An Investigation on the Effect of Polyethylene Oxide Concentration and Particle Size in Modulating Theophylline Release from Tablet Matrices

Polyethylene oxide has been researched extensively as an alternative polymer to hydroxypropyl methylcellulose (HPMC) in controlled drug delivery due to its desirable swelling properties and its availability in a number of different viscosity grades. Previous studies on HPMC have pointed out the importance of particle size on drug release, but as of yet, no studies have investigated the effect of particle size of polyethylene oxide (polyox) on drug release. The present study explored the relationship between polymer level and particle size to sustain the drug release. Tablets produced contained theophylline as their active ingredient and consisted of different polyethylene oxide particle size fractions (20-45, 45-90, 90-180 and 180-425 μm). It was shown that matrices containing smaller particle sizes of polyox produced harder tablets than when larger polyox particles were used. The release studies showed that matrices consisting of large polyox particles showed a faster release rate than matrices made from smaller particles. Molecular weight (MW) of the polymer was a key determining step in attaining sustained release, with the high MW of polyox resulting in a delayed release profile. The results showed that the effect of particle size on drug release was more detrimental when a low concentration of polyox was used. This indicates that care must be taken when low levels of polyox with different particle size fractions are used. More robust formulations could be obtained when the concentration of polyox is high. Differential scanning calorimetry (DSC) traces showed that particle size had no major effect on the thermal behaviour of polyox particles.

Preparation and scale up of extended-release tablets of bromopride

Reproducibility of the tablet manufacturing process and control of its pharmaceutics properties depends on the optimization of formulation aspects and process parameters. Computer simulation such as Design of Experiments (DOE) can be used to scale up the production of this formulation, in particular for obtaining sustained-release tablets. Bromopride formulations are marketed in the form of extended-release pellets, which makes the product more expensive and difficult to manufacture. The aim of this study was to formulate new bromopride sustained release formulations as tablets, and to develop mathematical models to standardize the scale up of this formulation, controlling weight and hardness of the tablets during manufacture according to the USP 34th edition. DOE studies were conducted using Minitab(tm) software. Different excipient combinations were evaluated in order to produce bromopride sustained-release matrix tablets. In the scale-up study, data were collected and variations in tableting machine parameters were measured. Data were processed by Minitab(tm) software, generating mathematical equations used for prediction of powder compaction behavior, according to the settings of the tableting machine suitable for scale-up purposes. Bromopride matrix tablets with appropriate characteristics for sustained release were developed. The scale-up of the formulation with the most suitable sustained release profile was established by using mathematical models, indicating that the formulation can be a substitute for the pellets currently marketed.

Designing a dynamic dissolution method: a review of instrumental options and corresponding physiology of stomach and small intestine

Development of new pharmaceutical compounds and dosage forms often requires in vitro dissolution testing with the closest similarity to the human gastrointestinal (GI) tract. To create such conditions, one needs a suitable dissolution apparatus and the appropriate data on the human GI physiology. This review discusses technological approaches applicable in biorelevant dissolutions as well as the physiology of stomach and small intestine in both fasted and fed state, that is, volumes of contents, transit times for water/food and various solid oral dosage forms, pH, osmolality, surface tension, buffer capacity, and concentrations of bile salts, phospholipids, enzymes, and Ca(2+) ions. The information is aimed to provide clear suggestions on how these conditions should be set in a dynamic biorelevant dissolution test.