Correlation between drug dissolution and polymer hydration: A study using texture analysis

New Insight into the Impact of Effervescence on Gel Layer Microstructure and Drug Release of Effervescent Matrices Using Combined Mechanical and Imaging Characterisation Techniques

Gel layer characteristics play a crucial role in hydrophilic hydroxypropyl methylcellulose (HPMC) matrix development. Effervescent agents have the potential to affect the gel layer microstructures. This study aimed to investigate the influence of effervescence on the microstructure of the gel layer around HPMC matrices using a combination of texture analysis and imaging techniques. The relationship with drug release profile and release mechanisms were also examined. The high amounts of effervescent agents promoted a rapid carbonation reaction, resulting in a high gel layer formation with a low gel strength through texture analysis. This finding was ascribed to the enhanced surface roughness and porosity observed under digital microscopy and microporous structure of the gel layer under scanning electron microscopy. The reconstructed three-dimensional images from synchrotron radiation X-ray tomographic microscopy notably exhibited the interconnected pores of various sizes from the carbonation reaction of effervescent and microporous networks, indicating the gel layer on the tablet surface. Notably, effervescence promoted the increase in interconnected porosities, which directly influenced the strength of the gel layer microstructure, drug release patterns and release mechanism of the effervescent matrix tablet. Therefore, combined mechanical characterisation and imaging techniques can provide new insights into the role of effervescent agents on the gel layer microstructure, and describe the relationship of drug release patterns and release mechanism of matrix tablets.

Investigation of the mucoadhesivity, swelling, and drug release mechanisms of indomethacin buccal tablets: effect of formulation variables

The purpose of this study was to investigate the effect of formulation variables on properties related to critical functionality for their use in indomethacin buccal tablets. Chitosan (CH), carbopol (PAA), and hydroxypropyl methyl cellulose (HPMC) concentration and filler type were evaluated as parameters for describing tablet hardness, swelling index, indomethacin release, and mucoadhesion in controlled release buccal tablets. Moreover, a 3² full factorial design was employed to study the effect of each polymer ratio in CH and PAA combination, which significantly influenced characteristics. A slower indomethacin release and a considerably larger degree of swelling were found for different concentrations of PAA or CH (p < 0.05). The buccal tablets formed a continuous gel layer while in contact with the aqueous medium undergoing a combination of swelling and erosion. In vitro drug release in simulated saliva (pH 6.75) appears to occur both by diffusion and a swelling-controlled mechanism, exhibiting anomalous, Case II type transport or Super Case II type transport. The diluent present in all study samples, mannitol (MAN), spray-dried lactose (SDL), and microcrystalline cellulose (MC) were believed to contribute minimally to hydrogel formation and drug release regulation. The dissolution values for the three co-excipients were decreasing order mannitol, spray-dried lactose, and microcrystalline cellulose. In conclusion, the type and concentration of all polymers seem to change the functionality of buccal tablets and it seems important to understand and characterize these excipients to fully predict the drug release, mucoadhesion, and swelling of buccal tablets.

Polyethylene oxide and its controlled release properties in hydrophilic matrix tablets for oral administration

Polymers are excipients that modify the rate of drug release from pharmaceutical dosage forms. Hydrophilic polymer-based controlled drug delivery system is more advantageous as compared to the conventional delivery system as it reduces the dosing frequency, improves therapeutic efficacy, reduces side-effects, and probably enhances patient compliance. Polyethylene oxide (PEO), a nonionic hydrophilic polymer, is one of the most widely used polymers for extending the drug release. This review mainly focuses on the PEO marketed by, but not limited to, The Dow Chemical Company under the trade name of POLYOX^TM. It is commercially available polyethylene oxide polymer existing in various molecular weight and viscosity grades depending upon the application. This study essentially discusses chemistry, physicochemical properties, and the impact of formulation and processing variables on the release of drug from hydrophilic PEO matrix tablets. Moreover, it also summarizes the stability, patents, and regulatory perspectives of POLYOX that can further influence the future developments of controlled release dosage forms.

Effects of Formulation and Process Variables on Gastroretentive Floating Tablets with A High-Dose Soluble Drug and Experimental Design Approach

To develop sustained release gastro-retentive effervescent floating tablets (EFT), a quality-based experimental design approach was utilized during the composing of a hydrophilic matrix loaded with a high amount of a highly water-soluble model drug, metformin HCl. Effects of the amount of polyethylene oxide WSR 303 (PEO), sodium bicarbonate, and tablet compression force were used as independent variables. Various times required to release the drug, tablet tensile strength, floating lag time, tablet ejection force, and tablet porosity, were selected as the responses. Polymer screening showed that PEO had the highest gel strength among the various tested polymers. Sodium bicarbonate had the most significant effect on the release rate and floating lag time by retarding the rate from the hydrophilic matrices, whilst tablet compression force and PEO exerted the greatest influence on tablet properties (p < 0.0001). The design space was built in accordance with the drug release profiles, tensile strength, and floating lag time, following failure probability analysis using Monte Carlo simulations. The kinetic modeling revealed that the release mechanism was best described by the Korsmeyer-Peppas model. Overall, the current study provided a perspective on the systematic approach of gastro-retentive EFT, loaded with highly water-soluble drugs by applying quality by design concepts.

Preparation and characterization of fast dissolving pullulan films containing BCS class II drug nanoparticles for bioavailability enhancement

The aim of this study is to assess pullulan as a novel steric stabilizer during the wet-stirred media milling (WSMM) of griseofulvin, a model poorly water-soluble drug, and as a film-former in the preparation of strip films via casting-drying the wet-milled drug suspensions for dissolution and bioavailability enhancement. To this end, pullulan films, with xanthan gum (XG) as thickening agent and glycerin as plasticizer, were loaded with griseofulvin nanoparticles prepared by WSMM using pullulan in combination with sodium dodecyl sulfate (SDS) as an ionic stabilizer. The effects of drug loading and milling time on the particle size and suspension stability were investigated, as well as XG concentration and casting thickness on film properties and dissolution rate. The nanosuspensions prepared with pullulan-SDS combination were relatively stable over 7 days; hence, this combination was used for the film preparation. All pullulan-based strip films exhibited excellent content uniformity (most <3% RSD) despite containing only 0.3-1.3 mg drug, which was ensured by the use of precursor suspensions with >5000 cP viscosity. USP IV dissolution tests revealed fast/immediate drug release (t80 < 30 min) from films <120 μm thick. Thinner films, films with lower XG loading, or smaller drug particles led to faster drug dissolution, while drug loading had no discernible effect. Overall, these results suggest that pullulan may serve as an acceptable stabilizer for media milling in combination with surfactant as well as a fast-dissolving film former for the fast release of poorly water-soluble drug nanoparticles.

Quantification of swelling and erosion in the controlled release of a poorly water-soluble drug using synchrotron X-ray computed microtomography

The hydration layer plays a key role in the controlled drug release of gel-forming matrix tablets. For poorly water-soluble drugs, matrix erosion is considered as the rate limiting step for drug release. However, few investigations have reported on the quantification of the relative importance of swelling and erosion in the release of poorly soluble drugs, and three-dimensional (3D) structures of the hydration layer are poorly understood. Here, we employed synchrotron radiation X-ray computed microtomography with 9-μm resolution to investigate the hydration dynamics and to quantify the relative importance of swelling and erosion on felodipine release by a statistical model. The 3D structures of the hydration layer were revealed by the reconstructed 3D rendering of tablets. Twenty-three structural parameters related to the volume, the surface area (SA), and the specific surface area (SSA) for the hydration layer and the tablet core were calculated. Three dominating parameters, including SA and SSA of the hydration layer (SA hydration layer and SSA hydration layer ) and SA of the glassy core (SA glassy core ), were identified to establish the statistical model. The significance order of independent variables was SA hydration layer > SSA hydration layer > SA glassy core , which quantitatively indicated that the release of felodipine was dominated by a combination of erosion and swelling. The 3D reconstruction and structural parameter calculation methods in our study, which are not available from conventional methods, are efficient tools to quantify the relative importance of swelling and erosion in the controlled release of poorly soluble drugs from a structural point of view.

Oral drug delivery systems comprising altered geometric configurations for controlled drug delivery

Recent pharmaceutical research has focused on controlled drug delivery having an advantage over conventional methods. Adequate controlled plasma drug levels, reduced side effects as well as improved patient compliance are some of the benefits that these systems may offer. Controlled delivery systems that can provide zero-order drug delivery have the potential for maximizing efficacy while minimizing dose frequency and toxicity. Thus, zero-order drug release is ideal in a large area of drug delivery which has therefore led to the development of various technologies with such drug release patterns. Systems such as multilayered tablets and other geometrically altered devices have been created to perform this function. One of the principles of multilayered tablets involves creating a constant surface area for release. Polymeric materials play an important role in the functioning of these systems. Technologies developed to date include among others: Geomatrix(®) multilayered tablets, which utilizes specific polymers that may act as barriers to control drug release; Procise(®), which has a core with an aperture that can be modified to achieve various types of drug release; core-in-cup tablets, where the core matrix is coated on one surface while the circumference forms a cup around it; donut-shaped devices, which possess a centrally-placed aperture hole and Dome Matrix(®) as well as "release modules assemblage", which can offer alternating drug release patterns. This review discusses the novel altered geometric system technologies that have been developed to provide controlled drug release, also focusing on polymers that have been employed in such developments.

Solid Dispersion Matrix Tablet Comprising Indomethacin-PEG-HPMC Fabricated with Fusion and Mold Technique

The purpose of this study is to fabricate the polyethylene glycol matrix tablet by mold technique. Indomethacin and hydroxypropylmethylcellulose were used as model drug and polymer, respectively, in PEG matrix system. The physical and drug release characteristics of developed matrix tablet were studied. This inert carrier system comprising 7:3 polyethylene glycol 4000: polyethylene glycol 400 could effectively enhance the solubility of indomethacin and an addition of hydroxypropylmethylcellulose could sustain the drug release. Scanning electron microscope photomicrograph indicated the drug diffusion outward through the porous network of this developed matrix tablet into the dissolution fluid. Least square fitting the experimental dissolution data to the mathematical expressions (power law, first-order, Higuchi's and zero-order) indicated the drug release kinetics primarily as Fickian diffusion. Both the enhancement of drug dissolution and the prolongation of the drug release could be achieved for aqueous insoluble drug such as, indomethacin, by using polyethylene glycol-hydroxypropylmethylcellulose matrix system prepared with melting and mold technique.

Characterization of indomethacin release from polyethylene glycol tablet fabricated with mold technique

The purpose of this study was to use polyethylene glycol as a carrier to improve the solubility of an aqueous insoluble drug by melting and molding method. The release of dissolved drug was designed to be subsequently sustained with an addition of xanthan gum. The release of indomethacin from the developed system into phosphate buffer pH 6.2 was conducted using the dissolution apparatus. This carrier system could effectively enhance the solubility of indomethacin and an addition of xanthan gum could sustain the drug release. Eudragit L100 film coating could protect the carrier not to be disturbed with HCl buffer pH 1.2 and could dissolve in phosphate buffer pH 6.2, therefore, the drug release from coated tablet was initially very low but subsequently gradually released and prolonged in phosphate buffer pH 6.2. Differential scanning calorimetry study indicated the amorphous state of drug in polyethylene glycol carrier. Scanning electron microscopy photomicrograph indicated the drug diffusion outward through the porous network of matrix tablets into the dissolution fluid and curve fitting signified that the drug release kinetic was Fickian diffusion.

Self-microemulsifiyng suppository formulation of β-artemether

Parasitic diseases are of immense global significance as around 30% of world's population experiences parasitic infections. Among these, malaria is the most life-threatening disease. Various routes of administration have been explored for delivering antimalarial actives. The present investigation aims at formulating self-microemulsifying suppositories of β-artemether with faster onset of action and prolonged effect to be administered by rectal route. These were compared with conventional polyethylene glycol suppositories with respect to melting range, rheology, texture analysis, disintegration time, self microemulsification time, particle size, and drug content. In vitro drug release was studied by using USP apparatus II. Further, the suppositories were evaluated in murine model against virulent rodent malaria parasite Plasmodium berghei wherein the developed self-microemulsifying suppositories could sustain the activity (94%) for 20 days post infection. The survival of animals was also better as compared to the conventional formulation.

Effect of drug solubility on polymer hydration and drug dissolution from polyethylene oxide (PEO) matrix tablets

The purpose of the study was to investigate the effect of drug solubility on polymer hydration and drug dissolution from modified release matrix tablets of polyethylene oxide (PEO). Different PEO matrix tablets were prepared using acetaminophen (ACE) and ibuprofen (IBU) as study compounds and Polyox WSR301 (PEO) as primary hydrophilic matrix polymer. Tablet dissolution was tested using the USP Apparatus II, and the hydration of PEO polymer during dissolution was recorded using a texture analyzer. Drug dissolution from the preparations was dependent upon drug solubility, hydrogel formation and polymer proportion in the preparation. Delayed drug release was attributed to the formation of hydrogel layer on the surface of the tablet and the penetration of water into matrix core through drug dissolution and diffusion. A multiple linear regression model could be used to describe the relationship among drug dissolution, polymer ratio, hydrogel formation and drug solubility; the mathematical correlation was also proven to be valid and adaptable to a series of study compounds. The developed methodology would be beneficial to formulation scientists in dosage form design and optimization.