Sustained release of acetaminophen from a heterogeneous mixture of two hydrophilic non-ionic cellulose ether polymers

Simultaneous Determination of Active Pharmaceutical Ingredients and Water-Soluble Polymers: Analysis of Dissolution Profiles from Sustained-Release Formulations and Mechanisms Involved

The dissolution behaviors of base excipients from sustained-release formulations have been investigated using various methodologies. However, the dissolution of polymers has not been fully evaluated because differences between formulations are still verified only by the release of active pharmaceutical ingredients (APIs). In our previous study, we proposed a quick and simultaneous analysis of dissolved APIs and water-soluble polymers by ultra HPLC using charged aerosol and photodiode array detectors. The purpose of this study was to verify whether the analysis system could be adapted to other water-soluble polymers. Dissolution tests were conducted using matrix model tablets prepared from three polymers and three APIs (propranolol, ranitidine, and cilostazol) with different solubilities. The dissolution profiles of the polymers and APIs were determined using the proposed analysis system and compared. The results clarified differences in the dissolution behaviors of the APIs and polymers. The polymers, especially hydroxypropyl cellulose, exhibited the dissolution properties characteristic of each model formulation. Propranolol and ranitidine showed the diffusion type, while cilostazol showed the erosion type release mechanism due to their different solubilities. The release of cilostazol was delayed in all models compared to the polymer, which may be due to the aggregation of cilostazol in the gel layer. This analytical method can be used to study the dissolution behavior (diffusion or erosion) of APIs from matrix tablets containing various polymers. This method will provide useful information on release control, which will make it easier and more efficient to design appropriate formulations and analyze the release mechanisms.

Budding Multi-matrix Technology-a Retrospective Approach, Deep Insights, and Future Perspectives

The human race is consistently striving for achieving good health and eliminate disease-causing factors. For the last few decades, scientists have been endeavoring to invent and innovate technologies that can substitute the conventional dosage forms and enable targeted and prolonged drug release at a particular site. The novel multi-matrix technology is a type of matrix formulation where the formulation is embraced to have a matrix system with multiple number of matrices. The MMX technology embraces with a combination of outer hydrophilic layer and amphiphilic/lipophilic core layer, within which drug is encapsulated followed by enteric coating for extended/targeted release at the required site. In comparison to conventional oral drug delivery systems and other drug delivery systems, multi-matrix (MMX) technology formulations afford many advantages. Additionally, it attributes for targeting strategy aimed at the colon and offers modified prolonged drug release. Thus, it has emerged rapidly as a potential alternative option in targeted oral drug delivery. However, the development of this MMX technology formulations is a exigent task and also has its own set of limitations. Due to its promising advantages and colon targeting strategy over the other colon targeted drug delivery systems, premier global companies are exploiting its potential. This article review deep insights into the formulation procedures, drug delivery mechanism, advantages, limitations, safety and efficacy studies of various marketed drug formulations of MMX technology including regulatory perspectives and future perspectives.

Superhydrophobic Surface for Enhancing the Bioavailability of Salbutamol Sulfate from Cross-Linked Microspheres: Formulation, Characterization, and in vivo Evaluation

Introduction

The aim of the work was to formulate salbutamol sulfate (SB) microspheres by using superhydrophobic surface (SHS) under different processing factors for improving its encapsulation efficiency, controling its release rate, and hence enhancing its bioavailability.

Methods

Cross-linked microspheres of chitosan (CN) and carrageenan (KN) were made on a SHS under a glutaraldehyde-saturated atmosphere. The formulations were designed and optimized based on 4² factorial design. Percentage encapsulation efficiency (%EE), particle size, swelling ratio, and in vitro release rate were characterized, and the in vivo performance of optimized formula was investigated in beagle dogs.

Results

The results showed that the prepared microspheres have a high %EE (97.11±0.78%) for F13. The swelling ratio was 4.2 at the end of the 8 hours for the optimized formula, and the in vitro release rate was controlled for 12 hours. In vivo study verified that there was a 1.61-fold enhancement in SB bioavailability from optimized formula (F13) compared to market tablet.

Conclusion

The study suggested that microspheres prepared from CN/KN crosslinking on an SHS using glutaraldehyde atmosphere is a promising technique that can encapsulate and sustain the release of water-soluble drugs such as SB in addition to improving its in vivo pharmacokinetic profile.

Applications of polymer blends in drug delivery

Background

Polymers are essential components of many drug delivery systems and biomedical products. Despite the utility of many currently available polymers, there exists a demand for materials with improved characteristics and functionality. Due to the extensive safety testing required for new excipient approval, the introduction and use of new polymers is considerably limited. The blending of currently approved polymers provides a valuable solution by which the limitations of individual polymers can be addressed.

Main body

Polymer blends combine two or more polymers resulting in improved, augmented, or customized properties and functionality which can result in significant advantages in drug delivery applications. This review discusses the rationale for the use of polymer blends and blend polymer-polymer interactions. It provides examples of their use in commercially marketed products and drug delivery systems. Examples of polymer blends in amorphous solid dispersions and biodegradable systems are also discussed. A classification scheme for polymer blends based on the level of material processing and interaction is presented.

Conclusion

The use of polymer blends represents a valuable and under-utilized resource in addressing a diverse range of drug delivery challenges. It is anticipated that new drug molecule development challenges such as bioavailability enhancement and the demand for enabling excipients will lead to increased applications of polymer blends in pharmaceutical products.

Graphical abstract

Formulation of Sustained Release Hydrophilic Matrix Tablets of Tolcapone with the Application of Sedem Diagram: Influence of Tolcapone's Particle Size on Sustained Release

Hydrophilic matrix tablets are a type of sustained release dosage form characterized by distributing a drug in a matrix that is usually polymeric. Tolcapone is a drug that inhibits the enzyme catechol-O-methyl transferase. In recent years, it has been shown that tolcapone is a potent inhibitor of the amyloid aggregation process of the transthyretin protein, and acts by stabilizing the structure of the protein, reducing the progression of familial amyloid polyneuropathy. The main objective of this study was to obtain a sustained release tablet of tolcapone for oral administration with a preferred dosage regimen of 1 administration every 12 or 24 h and manufactured, preferably, by direct compression. The SeDeM Diagram method has been used for the formulation development of hydrophilic matrix tablets. Given the characteristics of tolcapone, the excipient selected for the formation of the polymeric matrix was a high viscosity hydroxypropylmethylcellulose (Methocel^® K100M CR). A decrease in the particle size of tolcapone resulted in a slower dissolution release of the formulation when the concentration of the polymer Methocel^® K100M CR was below 29%. These surprising and novel results have given rise to patent number WO/2018/019997.

Hypromellose - A traditional pharmaceutical excipient with modern applications in oral and oromucosal drug delivery

Hydroxypropylmethylcellulose (HPMC), also known as Hypromellose, is a traditional pharmaceutical excipient widely exploited in oral sustained drug release matrix systems. The choice of numerous viscosity grades and molecular weights available from different manufacturers provides a great variability in its physical-chemical properties and is a basis for its broad successful application in pharmaceutical research, development, and manufacturing. The excellent mucoadhesive properties of HPMC predetermine its use in oromucosal delivery systems including mucoadhesive tablets and films. HPMC also possesses desirable properties for formulating amorphous solid dispersions increasing the oral bioavailability of poorly soluble drugs. Printability and electrospinnability of HPMC are promising features for its application in 3D printed drug products and nanofiber-based drug delivery systems. Nanoparticle-based formulations are extensively explored as antigen and protein carriers for the formulation of oral vaccines, and oral delivery of biologicals including insulin, respectively. HPMC, being a traditional pharmaceutical excipient, has an irreplaceable role in the development of new pharmaceutical technologies, and new drug products leading to continuous manufacturing processes, and personalized medicine. This review firstly provides information on the physical-chemical properties of HPMC and a comprehensive overview of its application in traditional oral drug formulations. Secondly, this review focuses on the application of HPMC in modern pharmaceutical technologies including spray drying, hot-melt extrusion, 3D printing, nanoprecipitation and electrospinning leading to the formulation of printlets, nanoparticle-, microparticle-, and nanofiber-based delivery systems for oral and oromucosal application. Hypromellose is an excellent excipient for formulation of classical dosage forms and advanced drug delivery systems. New methods of hypromellose processing include spray draying, hot-melt extrusion, 3D printing, and electrospinning.

Superhydrophobic Substrates for Ultrahigh Encapsulation of Hydrophilic Drug into Controlled-Release Polyelectrolyte Complex Beads: Statistical Optimization and In Vivo Evaluation

: In this work, ultrahigh drug-loaded chitosan (Ch)/K-carrageenan (Kc) polyelectrolyte complex (PEC) beads were formed in situ by cross-linking in a glutaraldehyde-saturated atmosphere and were prepared on superhydrophobic substrates fabricated by spraying glass surfaces with ready-made spray for domestic use (NeverWet^®). Verapamil hydrochloride (VP), a highly hydrophilic drug with a short biological half-life, was incorporated into a series of Ch-based and/or Ch/Kc-PEC-based beads to control its release profile in vivo. The formulation of VP-loaded beads was optimized using stepwise statistical designs based on a prespecified criterion. Several characteristics of the prepared beads, such as entrapment efficiency (EE%), in vitro drug release, swelling ratio, size and surface microstructure as well as molecular interactions between the drug and formulation ingredients, were investigated. In vivo pharmacokinetic (PK) studies were carried out using the rabbit model to study the ability of the optimized VP-loaded beads to control the absorption rate of VP. Results revealed that the prepared superhydrophobic substrates were able to fabricate VP-loaded beads with extremely high EE exceeding 90% w/w compared to only 27.80% when using conventional ionotropic gelation technique. PK results showed that the rate of VP absorption was well controlled following oral administration of the optimized beads to six rabbits compared to a marketed VP immediate release (IR) tablet, as evidenced by a 2.2-fold increase in mean residence time (MRT) and 5.24-fold extension in half value duration (HVD) over the marketed product without any observed reduction in the relative oral bioavailability.

Polymer Distribution and Mechanism Conversion in Multiple Media of Phase-Separated Controlled-Release Film-Coating

Phase-separated films of water-insoluble ethyl cellulose (EC) and water-soluble hydroxypropyl cellulose (HPC) can be utilized to tailor drug release from coated pellets. In the present study, the effects of HPC levels and the pH, type, ionic strength and osmolarity of the media on the release profiles of soluble metoprolol succinates from the EC/HPC-coated pellets were investigated, and the differences in drug-release kinetics in multiple media were further elucidated through the HPC leaching and swelling kinetics of the pellets, morphology (SEM) and water uptake of the free films and the interaction between the coating polymers and the media compositions. Interestingly, the drug release rate from the pellets in different media was not in agreement with the drug solubility which have a positive correlation with the drug dissolution rate based on Noyes–Whitney equation law. In particular, the drug release rate in acetate buffer at pH 4.5 was faster than that in other media despite the solubility of drug was relatively lower, regardless of the HPC levels. It may be attributed to the mutual effect between the EC and acetate buffer, which improved the permeability of the film. In contrast, the release of drug in HCl solution was dependent on the HPC levels. Increasing the levels of HPC increased the effects of hydrogen ions on the polymer of HPC, which resulted in a lower viscosity and strength of the gel, forming the larger size of pores in polymer films, thus increasing the drug diffused from the coating film. Further findings in phosphate buffer showed a reduction in the drug release compared to that in other media, which was only sensitive to the osmolarity rather than the HPC level and pH of the buffer. Additionally, a mathematical theory was used to better explain and understand the experimentally measured different drug release patterns. In summary, the study revealed that the effects of the media overcompensated that of the drug solubility to some extent for controlled-release of the coating polymers, and the drug release mechanism in multiple media depend on EC and HPC rather than on HPC alone, which may have a potential to facilitate the optimization of ideally film-coated formulations.

Evaluation of swelling processes of various natural polymer matrix tablets by X-ray computed tomography and controlled drug release

BACKGROUND

The swelling properties and the drug-release sustainability of pre-gelatinized starches (𝛼-starch) tablets depend on the polymer characteristics.

OBJECTBS

In order to clarify the drug release form, the natural polymers (NPs) were investigated. The relationship between drug release and swelling of natural polymers (NPs), the swelling processes of various starch polymers, were investigated using a drug-release test (DRT) and X-ray computed tomography (XCT). NPs consisting of various starches such as glutinous rice starch (GRS), corn starch (CS), and tapioca starch (TS) were used as additives for sustained drug-release tablets. Tablets consisted of 5% theophylline, 94% 𝛼-starch, and 1% magnesium stearate and were compressed at 6 kN. DRTs were measured in distilled water at 37 °C, and the drug concentrations were measured using UV (271 nm). Swelling ratio (R) profiles of the tablets during DRTs were evaluated based on XCT images.

RESULTS

The order of the drug-release rate constant of the tablets was TS < GRS < CS. XCT images of the tablets were measured during the DRTs, and CS, GRS, and TS tablets swelled and showed increased gel-layers, and then finally disintegrated at 6, 9, and 11 h, respectively.

CONCLUSION

The relationship between R profile and the % drug release of the tablets differed depending on the kind of NP used.

The influence of thermal treatment and type of insoluble poly(meth)acrylates on dissolution behavior of very soluble drug from hypromellose matrix tablets evaluated by multivariate data analysis

Hypromellose matrices exhibit extended burst effect immediately after contact with aqueous medium, especially when a water-soluble drug is incorporated. The objective of this study was to reduce burst effect and maintain complete dissolution of a very soluble levetiracetam over 12 h period from hypromellose K4M matrices to obtain zero-order kinetics. Desired changes were achieved by applying water dispersions of insoluble Eudragits^® (NE, NM, RL, RS) as a granulation liquid to the drug/microcrystalline cellulose mixture during high-shear granulation (non-thermal treated set) and consequently by thermally treating granules or final tablets (TT), respectively. Applying Eudragit^® water dispersions to the drug/microcrystalline cellulose mixture was recognized as an effective method of significantly reducing the burst release (25.4-33.7%) of levetiracetam in comparison with a reference sample without Eudragit^®. Multivariate data analysis showed that the addition of Eudragit^® reduced burst effect, increased fitting with zero-order kinetics, and supported matrix erosion as the supplementary mechanism to predominant diffusion. Moreover, resulting PCA sub-model revealed the addition of Eudragit^® RL and thermal treatment of tablets to be the most suitable method of all. For a 12 h dissolution profile, characterized by low burst effect and drug release close to 100% at the 12th hour, sample RL_TT was the most suitable.

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.

Interpenetrating hydrogels of O-carboxymethyl Tamarind gum and alginate for monitoring delivery of acyclovir

In this work, an interpenetrating hydrogel network was constructed using varying combination of O-carboxymethyl Tamarind gum (CTG) and alginate by Ca⁺² ion induced gelation method. The hydrogels were characterized by FTIR spectroscopy, Field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) and differential scanning calorimetry (DSC) analyses. The hydrogels were spherical in shape with rough surface textures. Depending on the alginate: CTG mass ratio, the hydrogel particles entrapped a maximum of ∼70% acyclovir. The drug release from interpenetrating hydrogels was 18-23% in HCl solution (pH1.2) in 2h. The drug release became faster in phosphate buffer solution (pH6.8) as the proportion of CTG was increased from 25% to 50%. However, the drug release was still slower than that observed for hydrogel particles of sodium alginate alone. Overall, the drug release tendency of the particles was higher in phosphate buffer solution than that in HCl solution. The non-Fickian drug release behavior was assumed after fitting the drug release data into Korsmeyer-Peppas model. The drug release was found to control by diffusion and swelling kinetics of the hydrogels. Thus, CTG gum could effectively retard drug release when used in combination with sodium alginate at an optimized mass ratio.

Advances in mechanistic understanding of release rate control mechanisms of extended-release hydrophilic matrix tablets

Approaches to characterizing and developing understanding around the mechanisms that control the release of drugs from hydrophilic matrix tablets are reviewed. While historical context is provided and direct physical characterization methods are described, recent advances including the role of percolation thresholds, the application on magnetic resonance and other spectroscopic imaging techniques are considered. The influence of polymer and dosage form characteristics are reviewed. The utility of mathematical modeling is described. Finally, how all the information derived from applying the developed mechanistic understanding from all of these tools can be brought together to develop a robust and reliable hydrophilic matrix extended-release tablet formulation is proposed.

Design and evaluation of effervescent floating tablets based on hydroxyethyl cellulose and sodium alginate using pentoxifylline as a model drug

The aim of this work was to design and evaluate effervescent floating gastro-retentive drug delivery matrix tablets with sustained-release behavior using a binary mixture of hydroxyethyl cellulose and sodium alginate. Pentoxifylline was used as a highly water-soluble, short half-life model drug with a high density. The floating capacity, swelling, and drug release behaviors of drug-loaded matrix tablets were evaluated in 0.1 N HCl (pH 1.2) at 37°C±0.5°C. Release data were analyzed by fitting the power law model of Korsmeyer-Peppas. The effect of different formulation variables was investigated, such as wet granulation, sodium bicarbonate gas-forming agent level, and tablet hardness properties. Statistical analysis was applied by paired sample t-test and one-way analysis of variance depending on the type of data to determine significant effect of different parameters. All prepared tablets through wet granulation showed acceptable physicochemical properties and their drug release profiles followed non-Fickian diffusion. They could float on the surface of dissolution medium and sustain drug release over 24 hours. Tablets prepared with 20% w/w sodium bicarbonate at 50-54 N hardness were promising with respect to their floating lag time, floating duration, swelling ability, and sustained drug release profile.

Design and in vivo evaluation of oxycodone once-a-day controlled-release tablets

The aim of present study was to design oxycodone once-a-day controlled-release (CR) tablets and to perform in vitro/in vivo characterizations. Release profiles to achieve desired plasma concentration versus time curves were established by using simulation software and reported pharmacokinetic parameters of the drug. Hydroxypropyl methylcellulose (HPMC) 100,000 mPa·s was used as a release modifier because the polymer was found to be resistant to changes in conditions of the release study, including rotation speed of paddle and ion strength. The burst release of the drug from the CR tablets could be suppressed by applying an additional HPMC layer as a physical barrier. Finally, the oxycodone once-a-day tablet was comprised of two layers, an inert HPMC layer and a CR layer containing drug and HPMC. Commercial products, either 10 mg bis in die (bid [twice a day]) or once-a-day CR tablets (20 mg) were administered to healthy volunteers, and calculated pharmacokinetic parameters indicated bioequivalence of the two different treatments. The findings of the present study emphasize the potential of oxycodone once-a-day CR tablets for improved patient compliance, safety, and efficacy, which could help researchers to develop new CR dosage forms of oxycodone.

Gemcitabine loaded biodegradable PLGA nanospheres for in vitro pancreatic cancer therapy

Pancreatic cancer is the fourth leading cancer with 85% mortality rate in USA alone and it is prevalent in many other developed and developing countries. Clinically, gemcitabine is prescribed as the first line chemotherapeutic drug for pancreatic cancer treatment. Gemcitabine-loaded poly(lactide-co-glycolide) (PLGA) nanospheres were synthesized and their physico-chemical properties were evaluated. The FESEM images showed that the gemcitabine loaded and blank nanospheres were 180 nm and 200 nm, respectively. The optimized encapsulation efficiency of gemcitabine was 15%. It was observed that 100% of gemcitabine was released from the PLGA nanospheres for 41 days in phosphate buffered saline (PBS) at pH7.4. The uptake of nanospheres in MiaPaCa-2 cells was studied using sulforhodamine B loaded PLGA nanospheres and our results showed that the nanospheres were taken up within 3h. Furthermore, the cytotoxicity of PLGA nanospheres loaded with gemcitabine showed a relative decrease in IC50 in MiaPaCa-2 and ASPC-1 pancreatic cancer cells in comparison to free gemcitabine. The study demonstrates that this system hold promise to improve the therapeutic efficacy of gemcitabine in vitro.

The design of controlled-release formulations resistant to alcohol-induced dose dumping--a review

The concomitant intake of alcoholic beverages together with oral controlled-release opioid formulations poses a serious safety concern since alcohol has the potential to alter the release rate controlling mechanism of the dosage form which may result in an uncontrolled and immediate drug release. This effect, known as alcohol-induced dose dumping, has drawn attention of the regulatory authorities. Thus, the Food and Drug Administration (FDA) recommends that in vitro drug release studies of controlled-release dosage forms containing drugs with narrow therapeutic range should be conducted in ethanolic media up to 40%. So far, only a limited number of robust dosage forms that withstand the impact of alcohol are available and the development of such dosage forms is still a challenge. This review deals with the physico-chemical key factors which have to be considered for the preparation of alcohol-resistant controlling dosage forms. Furthermore, appropriate matrix systems and promising technological strategies, which are suitable to prevent alcohol-induced dose dumping, are discussed.

Matrix tablets: the effect of hydroxypropyl methylcellulose/anhydrous dibasic calcium phosphate ratio on the release rate of a water-soluble drug through the gastrointestinal tract I. In vitro tests

Different hydroxypropyl methylcellulose (HPMC)/anhydrous dibasic calcium phosphate (ADCP) matrix tablets have been developed aiming to evaluate the influence of both components ratio in the control release of a water-soluble drug (theophylline). In order to characterise the matrix tablets, swelling, buoyancy and dissolution studies have been carried out in different aqueous media (demineralised water, progressive pH medium, simulated gastric fluid, simulated intestinal fluid and simulated colonic fluid). The HPMC/ADCP ratio has turned out to be the determinant in the matrix behaviour: the HPMC characteristic swelling behaviour was modulated, in some cases, by the ADCP characteristic acidic dissolution. When the HPMC/ADCP ratio was ≥0.69, buoyancy, continuous swelling and low theophylline dissolution rate from the matrices (H1, H2 and H3) were observed in all dissolution media. Consequently, these formulations could be adequate as gastro-retentive drug delivery systems. Additionally, HPMC/ADCP ratio ≤0.11 (H5 and H6) induces a pH-dependent drug release which could be applied to design control drug release enteric formulations (with a suitable enteric coating). Finally, a HPMC/ADCP ratio between 0.11 and 0.69 (H4) yield a gastrointestinal controlled drug release, due to its time-dependent buoyancy (7 h) and a total drug delivery in 17 h in simulated colonic fluid.

Collaboration between HPMC and NaCMC in order to reach the polymer critical point in theophylline hydrophilic matrices

Percolation theory has been applied in order to study the existence of critical points as well as the possibility to find a “combined percolation threshold” for ternary hydrophilic matrices prepared with HPMC, NaCMC, and theophylline. For this purpose, different batches of ternary as well as binary hydrophilic matrices have been prepared. Critical points have been found for binary hydrophilic matrices between 21.5 and 31.3% (v/v) of HPMC and between 39 and 54% (v/v) of NaCMC, respectively. In a previous work carried out with the same polymers but a much more soluble drug (KCl), it was demonstrated the existence of a partial collaboration between the polymers in order to establish the gel layer. In this work, it has been observed for the first time the need of a minimum concentration of one of the matrix-forming polymer (between 10 and 20% v/v, approximately) for establishing an effective collaboration.

Eudraginated polymer blends: a potential oral controlled drug delivery system for theophylline

Sustained release (SR) dosage forms enable prolonged and continuous deposition of the drug in the gastrointestinal (GI) tract and improve the bioavailability of medications characterized by a narrow absorption window. In this study, a new strategy is proposed for the development of SR dosage forms for theophylline (TPH). Design of the delivery system was based on a sustained release formulation, with a modified coating technique and swelling features aimed to extend the release time of the drug. Different polymers, such as Carbopol 71G (CP), sodium carboxymethylcellulose (SCMC), ethylcellulose (EC) and their combinations were tried. Prepared matrix tablets were coated with a 5 % (m/m) dispersion of Eudragit (EUD) in order to get the desired sustained release profile over a period of 24 h. Various formulations were evaluated for micromeritic properties, drug concentration and in vitro drug release. It was found that the in vitro drug release rate decreased with increasing the amount of polymer. Coating with EUD resulted in a significant lag phase in the first two hours of dissolution in the acidic pH of simulated gastric fluid (SGF) due to decreased water uptake, and hence decreased driving force for drug release. Release became faster in the alkaline pH of simulated intestinal fluid (SIF) owing to increased solubility of both the coating and matrixing agents. The optimized formulation was subjected to in vivo studies in rabbits and the pharmacokinetic parameters of developed formulations were compared with the commercial (Asmanyl(®)) formulation. Asmanyl(®) tablets showed faster absorption (t(max) 4.0 h) compared to the TPH formulation showing a t(max) value of 8.0 h. The C(max) and AUC values of TPH formulation were significantly (p < 0.05) higher than those for Asmanyl(®), revealing relative bioavailability of about 136.93 %. Our study demonstrated the potential usefulness of eudraginated polymers for the oral delivery of the sparingly soluble drug theophylline.

The influence of sodium carboxymethylcellulose on drug release from polyethylene oxide extended release matrices

Anionic polymer sodium carboxymethylcellulose (CELLOGEN® HP-HS and/or HP-12HS) was investigated for its ability to influence the release of three model drugs propranolol hydrochloride, theophylline and ibuprofen from polyethylene oxide (POLYOX™ WSR 1105 and/or Coagulant) hydrophilic matrices. For anionic ibuprofen and non-ionic theophylline, no unusual/unexpected release profiles were obtained from tablets containing a mixture of two polymers. However, for cationic propranolol HCl, a combination of polyethylene oxide (PEO) with sodium carboxymethylcellulose (NaCMC) produced a significantly slower drug release compared to the matrices with single polymers. The potential use of this synergistic interaction can be a design of new extended release pharmaceutical dosage forms with a more prolonged release (beyond 12 h) using lower polymer amount, which could be particularly beneficial for freely water-soluble drugs, preferably for once daily oral administration. In order to explain changes in the obtained drug release profiles, Fourier transform infrared absorption spectroscopy was performed. A possible explanation for the more prolonged propranolol HCl release from matrices based on both PEO and NaCMC may be due to a chemical bond (i.e. ionic/electrostatic intermolecular interaction) between amine group of the cationic drug and carboxyl group of the anionic polymer, leading to a formation of a new type/form of the active (i.e. salt) with sustained release pattern.

A pharma-robust design method to investigate the effect of PEG and PEO on matrix tablets

Even though polyethyleneoxide (PEO)-polyethyleneglycol (PEG) blends have been used widely for sustained release matrix tablets, evaluations of the effects of PEG or PEO on the matrix properties have been limited. In order to evaluate gelling behavior and drug release profiles of PEG, various contents of the polymers were investigated through a robust experimental design method. When exposed to an aqueous environment, the PEO-PEG matrix hydrated slowly and swelled, causing a thick gel layer to form on the surface, the thickness of which increased significantly depending on the PEG contents. Since polyacrylate plates were used for the study, the matrix was not completely hydrated and gelled even after 5h. However, the results could be applied to the time-oriented responses RD (robust design) models to obtain optimal settings and responses for the observed times. The optimal settings of PEO and PEG were 94.26 and 140.04 mg, respectively (PEG rate of 148.57%). Moreover, as the amount of PEG increased, the release rate also increased. When the formulation contained more than 150% of PEG, most of the drug loaded in the tablet was released in about 12 h. When the amount of PEG was less than 100%, the drug release rate was sustained significantly. Based on the RD optimization model for drug release, the optimal settings were PEG and PEO of 124.3 and 110 mg, respectively (PEG rate of 88.50%). Therefore, PEG rate of about 90-150% is suggested for matrix tablet formulations, and the exact ratio could be formulated according to the resulting tablet's properties.

Synchrotron X-ray microtomographic study of tablet swelling

Tablet swelling behaviour was investigated by following the movements of embedded glass microsphere tracers, using X-ray microtomography (XmicroT) with intense illumination from a synchrotron. Specimens were prepared using combinations of hydroxypropyl-methyl-cellulose (HPMC) and microcrystalline cellulose (MCC) or pre-gelatinised starch (PGS), three materials commonly used as excipients for compacted tablets. The results revealed significant differences in swelling behaviour due to excipient type and compaction conditions. In particular, a sudden change was observed from gel-forming behaviour of formulations containing PGS or high HPMC content, to more rapid expansion and disintegration for formulations above 70% MCC. Although some radial expansion was observable with the higher PGS formulations and during later stages of swelling, axial expansion (i.e. the reverse of the compaction process) appeared to dominate in most cases. This was most pronounced for the 10/90 HPMC/MCC specimens, which rapidly increased in thickness, while the diameter remained almost unchanged. The expansion appeared to be initiated by hydration and may be due to the relaxation of residual compaction stress. This occurred within 'expansion zones', which initially appeared as thin bands close to the compacted (upper and lower) faces, but gradually advanced towards the centre and spread around the sides of the tablets. These zones exhibited lower X-ray absorbance, probably because they contained significant amounts of bubbles, which were formed by air released from the swelling excipients. Although, in most cases, these bubbles were too small to be resolved (<60 microm), larger bubbles (diameter up to 1mm) were clearly evident in the rapidly swelling 10/90 HPMC/MCC specimens. It is suggested that the presence of these bubbles may affect subsequent water ingress, by increasing the tortuosity and occluding part of the gel, which may affect the apparent diffusion kinetics (i.e. Fickian or Case II). These observations also suggested that axial expansion, initiated by water ingress, may be an important mechanism during tablet swelling.

Compatibility Studies Between Ibuprofen or Ketoprofen with Cellulose Ether Polymer Mixtures Using Thermal Analysis

Differential scanning calorimetry (DSC) was used to investigate and detect incompatibilities between drugs such as: ibuprofen (IBU) or ketoprofen (KETO) with cellulose ether derivatives, which are frequently applied on controlled release dosage forms. Binary mixtures concerning methylcellulose (MC25) or hydroxypropylcellulose (HPC) with hydroxypropylmethylcellulose (HPMC) K15M or K100M in different ratios were prepared and evaluated by the appearance, shift, or disappearance of peaks and/or variations in the corresponding DeltaH values. According to the DSC results, binary mixtures between those polymers were found to be compatible, but their mixture with IBU or KETO, promotes a solid-solid interaction mainly with 1:1:1 (w/w) ratio (drug-excipient). However, when the drug:excipient interactions were detected, they were not found to affect the drug bioavailability. DSC was successfully employed to evaluate the compatibility of the drugs with the selected polymers.

Development of Novel Interpenetrating Network Gellan Gum-Poly(vinyl alcohol) Hydrogel Microspheres for the Controlled Release of Carvedilol

Novel interpenetrating polymeric network microspheres of gellan gum and poly(vinyl alcohol) were prepared by the emulsion cross-linking method. Carvedilol, an antihypertensive drug, was successfully loaded into these microspheres prepared by changing the experimental variables such as ratio of gellan gum:poly(vinyl alcohol) and extent of cross-linking in order to optimize the process variables on drug encapsulation efficiency, release rates, size, and morphology of the microspheres. Formation of interpenetrating network and the chemical stability of carvedilol after preparing the microspheres was confirmed by Fourier transform infrared spectroscopy. Differential scanning calorimetry and x-ray diffraction studies were made on the drug-loaded microspheres to investigate the crystalline nature of the drug after encapsulation. Results indicated a crystalline dispersion of carvedilol in the polymer matrix. Scanning electron microscopy confirmed the spherical nature and smooth surface morphology of the microspheres produced. Mean particle size of the microspheres as measured by laser light scattering technique ranged between 230 and 346 microm. Carvedilol was successfully encapsulated up to 87% in the polymeric matrices. In vitro release studies were performed in the simulated gastric fluid or simulated intestinal fluid. The release of carvedilol was continued up to 12 h. Dynamic swelling studies were performed in the simulated gastric fluid or simulated intestinal fluid, and diffusion coefficients were calculated by considering the spherical geometry of the matrices. The release data were fitted to an empirical relation to estimate the transport parameters. The mechanical properties of interpenetrating polymeric networks prepared were investigated. Network parameters such as molar mass between cross-links and cross-linking density for interpenetrating polymeric networks were calculated.

Role of Cellulose Ether Polymers on Ibuprofen Release from Matrix Tablets

Cellulose derivatives are the most frequently used polymers in formulations of pharmaceutical products for controlled drug delivery. The main aim of the present work was to evaluate the effect of different cellulose substitutions on the release rate of ibuprofen (IBP) from hydrophilic matrix tablets. Thus, the release mechanism of IBP with methylcellulose (MC25), hydroxypropylcellulose (HPC), and hydroxypropylmethylcellulose (HPMC K15M or K100M) was studied. In addition, the influence of the diluents lactose monohydrate (LAC) and beta-cyclodextrin (beta-CD) was evaluated. Distinct test formulations were prepared containing: 57.14% of IBP, 20.00% of polymer, 20.29% of diluent, 1.71% of talc lubricants, and 0.86% of magnesium stearate as lubricants. Although non-negligible drug-excipient interactions were detected from DSC studies, these were found not to constitute an incompatibility effect. Tablets were examined for their drug content, weight uniformity, hardness, thickness, tensile strength, friability, porosity, swelling, and dissolution performance. Polymers MC25 and HPC were found to be unsuitable for the preparation of this kind of solid dosage form, while HPMC K15M and K100M showed to be advantageous. Dissolution parameters such as the area under the dissolution curve (AUC), the dissolution efficiency (DE(20 h)), dissolution time (t 50%), and mean dissolution time (MDT) were calculated for all the formulations, and the highest MDT values were obtained with HPMC indicating that a higher value of MDT signifies a higher drug retarding ability of the polymer and vice-versa. The analysis of the drug release data was performed in the light of distinct kinetic mathematical models-Kosmeyer-Peppas, Higuchi, zero-, and first-order. The release process was also found to be slightly influenced by the kind of diluent used.

Formulation variables influencing drug release from layered matrix system comprising chitosan and xanthan gum

The purpose of this study was to investigate the formulation variables influencing the drug release from the layered tablets containing chitosan and xanthan gum as matrix component. Increasing the amount of lactose could diminish pH sensitive release behavior of these matrix tablets. Effect of formulation variables on drug release from the prepared three-layered matrix tablets was investigated. The amount of drug loading did not affect the drug release which was influenced by the hydrodynamic force and the matrix composition. An increase in stirring rate correspondingly increased the release rate. Moreover, incorporation of soluble diluents in core or barrier could enhance the drug release. Least square fitting the experimental dissolution data to the mathematical expressions (power law, first order, Higuchi's and zero order) was carried out to study the drug release mechanism. Most dissolution profiles of the prepared three-layered tablets provided a better fit to zero order kinetic than to first order kinetic and Higuchi's equation.

Drug release and swelling kinetics of directly compressed glipizide sustained-release matrices: establishment of level A IVIVC

The purpose of this study was to examine a level A in vitro-in vivo correlation (IVIVC) for glipizide hydrophilic sustained-release matrices, with an acceptable internal predictability, in the presence of a range of formulation/manufacturing changes. The effect of polymeric blends of ethylcellulose, microcrystalline cellulose, hydroxypropylmethylcellulose, xanthan gum, guar gum, Starch 1500, and lactose on in vitro release profiles was studied and fitted to various release kinetics models. Water uptake kinetics with scanning electron microscopy (SEM) was carried out to support the drug release mechanism. An IVIVC was established by comparing the pharmacokinetic parameters of optimized (M-24) and marketed (Glytop-2.5 SR) formulations after single oral dose studies on white albino rabbits. The matrix M-19 (xanthan:MCC PH301 at 70:40) and M-24 (xanthan:HPMC K4M:Starch 1500 at 70:25:15) showed the glipizide release within the predetermined constraints at all time points with Korsmeyer-Peppas' and zero-order release mechanism, respectively. Kopcha model revealed that the xanthan gum is the major excipient responsible for the diffusional release profile and was further supported by SEM and swelling studies. A significant level A IVIVC with acceptable limits of prediction errors (below 15%) enables the prediction of in vivo performance from their in vitro release profile. It was concluded that proper selection of rate-controlling polymers with release rate modifier excipients will determine overall release profile, duration and mechanism from directly compressed matrices.

Evaluation of rate of swelling and erosion of verapamil (VRP) sustained-release matrix tablets

Tablets manufactured in-house were compared to a marketed sustained-release product of verapamil to investigate the rate of hydration, erosion, and drug-release mechanism by measuring the wet and subsequent dry weights of the products. Swelling and erosion rates depended on the polymer and granulating fluid used, which ultimately pointed to their permeability characteristics. Erosion rate of the marketed product was highest, which suggests that the gel layer that formed around these tablets was weak as opposed to the robust and resistant layers of test products. Anomalous and near zero-order transport mechanisms were dominant in tests and commercial product, respectively.

Matrices containing NaCMC and HPMC 1. Dissolution performance characterization

In this study hydroxypropylmethylcellulose (HPMC) and sodium carboxymethylcellulose (NaCMC) were used as polymeric carriers to improve controlled release performances of matrix tablets containing a soluble drug. The drug release behaviour of the systems containing these two polymers mixture and each material separately was investigated. To evaluate the effect of the dissolution medium pH, on the drug release performance, release tests were conducted at pH 1, 4.5 and 6.8. In vitro release studies demonstrated that the mixture of the two cellulose derivatives enables a better control of the drug release profiles at pH 4.5 and at 6.8 both in term of rate and mechanism. Texture analysis on the swollen tablets helps to understand drug release kinetic and mechanism. In fact, the results obtained confirm that a gel, which is characterized by high strength and consistence is less susceptible to erosion and chains disentanglement and the drug release mechanism is mainly governed by diffusion. On the contrary, gels, which show a low strength and texture, have low resistance to the fluid erosion action and the release of the active molecule is manly due to polymer relaxation and chains disentanglement moving the drug delivery kinetic towards an erosion/relaxation mechanism.

Formulation, release characteristics and bioavailability of novel monolithic hydroxypropylmethylcellulose matrix tablets containing acetaminophen

Effect of incorporating pharmaceutical excipients on the in vitro release profiles and the release mechanism of monolithic hydroxypropylmethylcellulose (4000 cps) matrix tablets (m-HPMC tablets) in terms of mimicking the dual drug release character of bi-layered Tylenol ER tablets was studied. We also compared the in vitro release profiles of optimized m-HPMC matrix tablet and Tylenol ER tablet in water, pH 1.2 gastric fluid, and pH 6.8 intestinal fluid, and in vivo drug bioavailabilities in healthy human volunteers. Acetaminophen was used as the model drug. The m-HPMC tablets were prepared using a wet granulation method followed by direct compression. Release profiles and swelling rates of m-HPMC tablets were found to be highly influenced by the types and amounts of pharmaceutical excipients incorporated. Starch 1500 (Prejel) and sodium lauryl sulfate (SLS) played a key role in determining the dissolution rate of m-HPMC tablets. Additional excipients, i.e., microcrystalline cellulose (Avicel PH101) and NaH2PO4 were used to tune the release profiles of m-HPMC tablets. The effect of pharmaceutical excipients on drug release from HPMC-based matrix tablets was found to be mainly due to a change in hydrophilic gel expansion and on physical interactions between the drug and HPMC. The optimized m-HPMC tablet with a balanced ratio of Prejel, SLS, Avicel PH101, and NaH2PO4 in the formulation showed dual release profiles in water, pH 1.2 gastric fluid, and pH 6.8 intestinal fluid in vitro. Dual release was defined as immediate drug release within few minutes followed by extended release over 8 h. The similarity factors of m-HPMC tablets and bi-layered Tylenol ER tablets were 79.8, 66.1, and 82.7 in water, gastric fluid and intestinal fluid, respectively, indicating the equivalence of the two release profiles. No significant in vivo bioavailability differences were observed in healthy human volunteers. The developed m-HPMC tablet with dual release characteristics can be easily prepared using a conventional high-speed tablet machine and could provide an alternative to commercially available bilayered Tylenol ER tablets.

Controlled-release matrix tablets of ibuprofen using cellulose ethers and carrageenans: effect of formulation factors on dissolution rates

The study was conducted to investigate the effects of carrageenans, and cellulose ethers on the drug release rates of ibuprofen controlled-release tablet matrices prepared by direct compression. Polymer blends containing carrageenans or cellulose ethers were used for the formulation and the effect of varying the polymer concentration on the release of the drug was studied. Other factors such as changes in surface topography of the matrices due to hydration were observed using a cryogenic scanning electron microscopy technique. Multiple regression analysis was used to predict the time for 50% release (t50) as a function of the concentration of the polymers used. Most of the formulations showed linear release profiles (r(2)>or=0.96-0.99) and sustained the release of ibuprofen over 12-16 h. The highest t50 (9.3 h) was for the formulation that contained a blend of 1:2 ratio of Viscarin and HPMC, while the lowest (3 h) was for the matrices that contained a 2:1 ratio of methylcellulose and Gelcarin. The majority of the matrix tablets that contained 10% polymer disintegrated prematurely. Of all the polymer blends that were investigated, the combination of Viscarin and HPMC gave almost linear release profiles over the entire range of concentration that was studied. The least effective combination was methylcellulose in combination with HPMC. Most of the formulations released ibuprofen by an anomalous (non-Fickian) transport mechanism, except those matrices that contained methylcellulose and Gelcarin (in a 1:1 and 1:2 ratio), which showed zero-order release.