Investigation of critical factors affecting mechanical characteristics of press-coated tablets using a compaction simulator.

Press-coated tablets have become an indispensable dosage form in chronotherapeutic drug delivery. Drug release from press-coated tablets has been extensively studied, yet there is little knowledge about their mechanical characteristics. This study aimed to systematically investigate the effects of critical factors on the structure, layer adhesion, and delamination tendency of the tablets. Material elasticity was found to play an important role in determining tablet structure in that excessive elastic mismatch between core and shell materials caused tablet defects during decompression and ejection. Unlike bilayer tablets, the overall strength of press-coated tablets was more affected by binding capacity of coating materials than by the core properties. Shell/core ratio was another factor affecting tablet integrity against external stresses. To mitigate the risk of delamination, poor layer adhesion must be compensated by increasing the coating thickness or enhanced by optimizing the formulation and process (e.g., core plasticity/brittleness, initial core solid fraction, and compression speed). X-ray micro-computed tomography revealed the presence of a shell-core gap and inhomogeneous density distribution within the tablet where the side coat appeared as the least dense and weakest region. These findings will enable the improvement of tablet quality and widen the application of press coating in industrial manufacturing.

Development of novel bilayer gastroretentive tablets based on hydrophobic polymers.

This study aimed to develop a bilayer gastroretentive (GR) tablet containing an insoluble drug and ascertain the potential of using hydrophobic polymers in GR matrix systems. Highly porous tablets were prepared using a camphor-based sublimation technique. After the screening of several commonly used polymers, two types of GR layers, a conventional hydrophilic GR layer and a hydrophobic GR layer, were designed. The optimal drug layer comprising Metolose® 90SH-100SR and dicalcium phosphate provided not only a gradual matrix erosion but also high strength after hydration. Regarding the GR layers, the hydrophobic layer based on Kollidon® SR was superior to the hydrophilic layer made of PEO 7 M in terms of wet strength, implying a higher resistance to mechanical stresses upon water absorption. Also, the excellent tableting properties of Kollidon® SR and the effects of curing in improving its matrix hardness resulted in porous tablets with better mechanical strength. Moreover, good flowability and low cohesion of Kollidon® SR formulation were advantageous in direct compression. In conclusion, novel bilayer GR tablets were successfully developed, indicating the potential for widening the application of GR systems to insoluble drugs. The results also suggested numerous advantages of incorporating Kollidon® SR into the production of GR tablets.

Swellable and porous bilayer tablet for gastroretentive drug delivery: Preparation and in vitro-in vivo evaluation.

The purpose of this study was to develop a novel gastroretentive drug delivery system with immediate buoyancy and high wet strength. The proposed bilayer tablet was composed of a drug layer and a highly porous and swellable gastroretentive (GR) layer. The highly porous GR layer was prepared by sublimating the volatile materials after compaction with swellable polymers. This pore-forming process decreased the density of the GR layer and enabled the tablet to float immediately on the dissolution media. The GR layer formulation was optimized by comparing the swelling, erosion, and mechanical properties of candidate swellable polymers. The release rates were conveniently controlled by changing the polymer content in the drug layer, while the swelling and floating properties were provided by the GR layer. The application of percolation theory revealed that the polymer content above the estimated threshold was required for a reliable drug release profile. In vivo study in fed beagle dogs confirmed the enhanced gastric retention time of the tablets compared to that of conventional single layer tablets. Taken together, our data suggest that the proposed system can be a promising platform technology with superior GR properties and a convenient formulation process.

Use of roller compaction and fines recycling process in the preparation of erlotinib hydrochloride tablets.

This study focuses on improving the manufacturing process for a generic immediate-release tablet containing erlotinib hydrochloride by adding a fines recycling process during roller compaction. Due to the large fraction of small-sized API particles, the starting powder mixture was inconsistently fed into the roller compactor. Consequently, poorly flowing granules with a high ratio of fines were produced. A fines recycling step was, therefore, added to the existing roller compaction process to minimize the risks caused by the poor granule flow. A laboratory scale roller compactor and a tablet simulator were used to prepare granules at various process conditions. The effect of dry granulation parameters on size distribution, API distribution, powder flow, compaction properties, and dissolution profile was evaluated. The granule batch after fines recycling had markedly improved size distribution and flowability while maintaining acceptable tablet tensile strength and rapid dissolution profile. The application of the fines recycling process at commercial scale resulted in reliable dissolution performance and batch-to-batch consistency, which were further confirmed by bioequivalence to the reference product. Understanding how granule properties are impacted by the fines recycling process may enable fine-tuning of the dry granulation process for optimal product quality.

Formulation and evaluation of carrier-free dry powder inhaler containing sildenafil.

Pulmonary delivery of sildenafil for the treatment of pulmonary arterial hypertension could overcome the limitations of intravenous and oral administration routes, such as poor patient compliance and systemic side effects. In this study, a carrier-free dry powder inhaler (DPI) formulation was developed, using spray drying technique and L-leucine as a dispersibility enhancer. Sildenafil citrate salt and sildenafil free base were evaluated for drug transport using a Calu-3 cell model, and their suitability for DPI production by spray drying was tested. Characteristics of the resultant carrier-free DPI powders were examined, namely crystallinity, morphology, size distribution, density, zeta potential, and aerodynamic performance. A Box-Behnken design was adopted to optimize the formulation and process conditions, including leucine amount, fraction of methanol in spraying solvent, and inlet temperature. While both sildenafil forms exhibited sufficient permeability for lung absorption, only sildenafil base resulted in DPI powders which were stable for 6 months. The introduction of leucine into the formulations effectively enhanced aerodynamic performance of the powders and particles with favorable size, shape, and density were produced. The optimal DPI formulation determined from experimental design possesses excellent aerodynamic performance with 89.39% emitted dose and 80.08% fine particle fraction, indicating the possibility of incorporating sildenafil into carrier-free DPIs for pulmonary delivery.

Preparation and evaluation of non-effervescent gastroretentive tablets containing pregabalin for once-daily administration and dose proportional pharmacokinetics.

The main purpose of this study was to develop gastroretentive tablets with floating and swelling properties for once-daily administration of pregabalin. The non-effervescent floating and swelling tablets were prepared using wet granulation and compaction, which are widely used and easily accessible. All formulations showed sustained release patterns and maintained buoyancy for over 24 h. The amount of hydroxypropyl methylcellulose and crospovidone were found to be critical factors affecting in vitro dissolution and floating properties of the prepared tablets. The optimized tablets containing 300 mg of pregabalin started to float within 3 min and swelled above 12.8 mm, the reported pyloric sphincter diameter during the fed state, in all dimensions including length, width, and thickness. In vivo results in beagle dogs indicated that the optimized formulations are suitable as once-daily dosage forms, and dose proportionality was observed in doses ranging from 75 to 300 mg. Additionally, the dogs administered with the formulation having poor in vitro gastroretentive properties showed highly variable and reduced extent of absorption, signifying the necessity of the gastroretentive drug delivery system. In conclusion, the developed non-effervescent floating tablets are promising candidates for once-daily delivery of pregabalin.

Application of continuous twin screw granulation for the metformin hydrochloride extended release formulation.

This study focuses on evaluating the potential of transferring from a batch process to continuous process for manufacturing of the extended release formulation. Metformin hydrochloride (HCl) was used in the model formulation which was intended to contain the high amount of hydrophilic drug. The effects of barrel temperature, binder type, powder feed rate, and screw speed on granule properties (size and strength) and torque value in twin screw granulation were investigated. Due to the high content of hydrophilic model drug, the granules prepared at a higher temperature with HPMC binding solution had the narrower size distribution and greater strength than the granules prepared with distilled water as a binding solution. After continuous drying and milling steps, the granules (continuous process) satisfied the fundamental purpose of granulation with size and flowability, despite different shape compared with the granules (batch process). Furthermore, there were no significant differences between two granulation processes in tablet properties, such as tablet hardness and in vitro release. The considerations and strategies used in this study to transfer from a batch to continuous process can be applied to other existing formulations based on high shear granulation to enable rapid process transfer in the pharmaceutical industry.

Highly lipophilic pluronics-conjugated polyamidoamine dendrimer nanocarriers as potential delivery system for hydrophobic drugs.

In the study, four kinds of pluronics (P123, F68, F127 and F108) with varying hydrophilic-lipophilic balance (HLB) values were modified and conjugated on 4th generation of polyamidoamine dendrimer (PAMAM). The obtained results from FT-IR, 1H NMR and GPC showed that the pluronics effectively conjugated on the dendrimer. The molecular weight of four PAMAM G4.0-Pluronics and its morphologies are in range of 200.15-377.14kDa and around 60-180nm in diameter by TEM, respectively. Loading efficiency and release of hydrophobic fluorouracil (5-FU) anticancer drug were evaluated by HPLC; Interesting that the dendrimer nanocarrier was conjugated with the highly lipophilic pluronic P123 (G4.0-P123) exhibiting a higher drug loading efficiency (up to 76.25%) in comparison with another pluronics. Live/dead fibroblast cell staining assay mentioned that all conjugated nanocarriers are highly biocompatible. The drug-loaded nanocarriers also indicated a highly anti-proliferative activity against MCF-7 breast cancer cell. The obtained results demonstrated a great potential of the highly lipophilic pluronics-conjugated nanocarriers in hydrophobic drugs delivery for biomedical applications.