Development of a single unit extended release formulation for ZK 811 752, a weakly basic drug

Kollidon® SR: Formulation techniques and drug delivery applications

Kollidon® SR is one of the recent versatile coprocessed excipients in the formulation of modified-release dosage forms. It is prepared by co-spray drying aqueous dispersions of polyvinylacetate and polyvinylpyrrolidone. This article gives a critical review of the physicochemical attributes and technological properties of Kollidon® SR. The current review discusses various technological approaches used in the formulation with Kollidon® SR, from conventional ones like direct compaction and wet granulation to more advanced methodologies such as 3D printing, electrospinning and hot-melt extrusion. The review further elaborates on the influence of the major factors on drug release kinetics from Kollidon® SR-based formulations. Furthermore, this review unravels the potential of Kollidon® SR in the development of site-targeted oral drug delivery systems and focuses on its adaptability to other routes of administration. Further, the review deals with the considerations to be made regarding stability to make sure the formulations based on Kollidon® SR are reliable.

Investigations on Compaction Behavior of Kollidon®SR-Based Multi-component Directly Compressed Tablets for Preparation of Controlled Release Diclofenac Sodium

The physics of tablets mixtures has gained much attention lately. The purpose of this work is to evaluate the compaction properties of Kollidon® SR (KSR) in the presence of different excipients such as Microcrystalline cellulose (MCC), Monohydrous lactose (MH Lactose), Poly (vinyl acetate) (PVA100), and a water-soluble drug Diclofenac sodium (DNa) to prepare once daily formulation. Tablets were prepared using direct compression and were compressed into flat-faced tablets using hydraulic press at various pressures. The combination of MCC and KSR in the tablets showed reduced porosity, and almost constant low Py values as KSR levels increased; also, KSR-DNa tablets had higher percentage porosity and crushing strength values than KSR-MH Lactose tablets. The crushing strengths of KSR-MCC tablets were larger than those of KSR-DNa tablets. Ternary mixture tablets comprised of KSR-MCC-DNa showed decreased porosities and low Py values as the percentage of KSR increased especially at high compression pressures but had higher crushing strengths compared to KSR-DNa or MCC-DNa binary tablets. KSR-MH Lactose-DNa ternary tablets experienced lower porosities and crushing strengths compared to KSR-MCC-DNa tablets. Quaternary tablets of KSR-PVA100-MCC-DNa showed lower porosity and Py values than quaternary tablets obtained using similar proportion of MH Lactose instead of MCC. In conclusion, optimum quaternary tablets were obtained with optimum crushing strengths, relatively low Py, and moderate percentage porosities among all prepared quaternary tablets. The drug release of the optimum quaternary tablets demonstrated similar in vitro release profile compared to that of the marketed product with a mechanism of release that follows Korsmeyer-Peppas model.

Experimental and Theoretical Study on Theobromine Solubility Enhancement in Binary Aqueous Solutions and Ternary Designed Solvents

The solubility of theobromine was studied both experimentally and theoretically. The solubility was determined spectrophotometrically at 25 °C in neat organic solvents, aqueous binary mixtures, Natural Deep Eutectic Solvents (NADES) and ternary NADES mixtures with water. It was found that addition of water in unimolar proportions with some organic solvents increases theobromine solubility compared to neat solvents. Additionally, using NADES results in a solubility increase of the studied compound not only in relation to water but also DMSO. The addition of water (0.2 molar fraction) to NADES is responsible for an even larger increase of solubility. The measured solubilities were interpreted in terms of three theoretical frameworks. The first one-belonging to the set of data reduction techniques-proved to be very efficient in quantitative back-computations of excess solubility of theobromine in all studied systems. The default approach utilizing the well-recognized COSMO-RS (Conductor-like Screening Model for Real Solvents) framework offered at most a qualitative solubility description. The extended search for possible contacts provided evidence for the existence of many intermolecular complexes that alter the electron density of the solute molecule, thus influencing solubility computations. Taking into account such intermolecular contacts by using the COSMO-RS-DARE (Conductor-like Screening Model for Realistic Solvation-Dimerization, Aggregation, and Reaction Extension) framework seriously increased the accuracy of solubility computations.

Solvent Screening for Solubility Enhancement of Theophylline in Neat, Binary and Ternary NADES Solvents: New Measurements and Ensemble Machine Learning

Theophylline, a typical representative of active pharmaceutical ingredients, was selected to study the characteristics of experimental and theoretical solubility measured at 25 °C in a broad range of solvents, including neat, binary mixtures and ternary natural deep eutectics (NADES) prepared with choline chloride, polyols and water. There was a strong synergistic effect of organic solvents mixed with water, and among the experimentally studied binary systems, the one containing DMSO with water in unimolar proportions was found to be the most effective in theophylline dissolution. Likewise, for NADES, the addition of water (0.2 molar fraction) resulted in increased solubility compared to pure eutectics, with the highest solubilisation potential offered by the composition of choline chloride with glycerol. The ensemble of Statistica Automated Neural Networks (SANNs) developed using intermolecular interactions in pure systems has been found to be a very accurate model for solubility computations. This machine learning protocol was also applied as an extensive screening for potential solvents with higher solubility of theophylline. Such solvents were identified in all three subgroups, including neat solvents, binary mixtures and ternary NADES systems. Some methodological considerations of SANNs applications for future modelling were also provided. Although the developed protocol is focused exclusively on theophylline solubility, it also has general importance and can be used for the development of predictive models adequate for solvent screening of other compounds in a variety of systems. Formulation of such a model offers rational guidance for the selection of proper candidates as solubilisers in the designed solvents screening.

Spray Drying for Direct Compression of Pharmaceuticals

Tableting by direct compression (DC) is one of the simplest and most cost-effective drug manufacturing approaches. However, most active pharmaceutical ingredients (APIs) and excipients lack the compression and flow properties required to meet the needs of high-speed industrial tablet presses. Therefore, the majority of DC APIs and excipients are modified via processing/co-processing particle engineering techniques to boost their properties. Spray drying is one of the most commonly employed techniques to prepare DC grades of APIs and excipients with prominent advantages. This review aims to present an overview of the commercially marketed and investigationally-prepared DC APIs and excipients produced by spray drying.

Sustained release dosage form of noscapine HCl using hot melt extrusion (HME) technique: formulation and pharmacokinetics

Sustained release formulation of noscapine (Nos) HCl could be useful in maintaining plasma Nos HCl level for prolonged period of time, which is important for chemo-sensitization. However, weakly basic drugs like Nos HCl have pH-dependent solubility. Therefore, the purpose of this study was to achieve pH-independent drug release by developing the sustained release dosage form of Nos HCl using biodegradable polymer Eudragit RLPO and FDA-approved pH modifier citric acid (CA) by hot melt extrusion (HME) technique. Nos HCl was successfully formulated using 10% CA with 91.2 ± 1.34% drug recovery through the extruder. X-ray diffraction (XRD) results showed that drug was completely dispersed in the polymer and changed to amorphous from its crystalline form. In vitro drug release studies in pH 6.8 buffer showed that formulation containing 10% CA released 70.99 ± 3.85% drug in 24 h after initial burst release of 40.04 ± 2.39% compared to formulation without CA. Furthermore, in vivo pharmacokinetic data showed the sustained release plasma concentration time curve with significant (p < 0.05) increase in area under curve (AUC) in Nos HCl extrudate compared to Nos HCl solution. Overall, HME can be used to enhance the bioavailability and achieve the pH-independent solubility of weakly basic drugs like Nos HCl. Graphical abstract.

Optimization, thermodynamic characteristics and solubility predictions of natural deep eutectic solvents used for sulfonamide dissolution

The limited water solubility of sulfonamides provokes a search for new solvents offering not only increased solubility but also environmental and health safety. Therefore, six sulfonamides were studied in a series of natural deep eutectic solvents (NADES) comprising choline chloride with multi-hydroxyl compounds. Experimental screening aimed at finding the optimized NADES composition revealed that unimolar proportion of choline chloride and glycerol offers the highest solubility advantage, equal up to 43 times compared with water at 37 °C. Besides, quantum chemistry computations based on the COSMO-RS protocol were conducted in order to gain an insight into the thermodynamic characteristics of the systems and to explain the origin of the observed solubility increase. It was found that the factor responsible for the solubility gain in NADES are the interactions between choline chloride and sulfonamide drug molecules, having the highest affinities expressed in terms of Gibbs free energy of corresponding reactions. Finally, utilizing the obtained results together with artificial neural networks led to a perfect match between experimental and predicted solubility, documented by the mean absolute percentage error value below 2.5%. The developed protocol seems to be so general and accurate that screening of potential new API-NADES systems can be significantly simplified.

Natural Deep Eutectic Solvents as Agents for Improving Solubility, Stability and Delivery of Curcumin

Purpose

Study on curcumin dissolved in natural deep eutectic solvents (NADES) was aimed at exploiting their beneficial properties as drug carriers.

Methods

The concentration of dissolved curcumin in NADES was measured. Simulated gastrointestinal fluids were used to determine the concentration of curcumin and quantum chemistry computations were performed for clarifying the origin of curcumin solubility enhancement in NADES.

Results

NADES comprising choline chloride and glycerol had the highest potential for curcumin dissolution. This system was also successfully applied as an extraction medium for obtaining curcuminoids from natural sources, as well as an effective stabilizer preventing curcumin degradation from sunlight. The solubility of curcumin in simulated gastrointestinal fluids revealed that the significant increase of bioavailability takes place in the small intestinal fluid.

Conclusions

Suspension of curcumin in NADES offers beneficial properties of this new liquid drug formulation starting from excreting from natural sources, through safe storage and ending on the final administration route. Therefore, there is a possibility of using a one-step process with this medium. The performed quantum chemistry computations clearly indicated the origin of the enhanced solubility of curcumin in NADES in the presence of intestinal fluids. Direct intermolecular contacts leading to hetero-molecular pairs with choline chloride and glycerol are responsible for elevating the bulk concentration of curcumin. Choline chloride plays a dominant role in the system and the complexes formed with curcumin are the most stable among all possible homo- and hetero-molecular pairs that can be found in NADES-curcumin systems.

Solubility advantage of sulfanilamide and sulfacetamide in natural deep eutectic systems: experimental and theoretical investigations

Objective: The aim of this study was to explore the possibility of using natural deep eutectic solvents (NADES) as solvation media for enhancement of solubility of sulfonamides, as well as gaining some thermodynamic characteristics of the analyzed systems. Significance: Low solubility of many active pharmaceutical ingredients is a well-recognized difficulty in pharmaceutical industry, hence the need for different strategies addressing this problem. Among such strategies, those that are environmentally and economically beneficial are of particular interest. Methods: The solubility of sulfanilamide and sulfacetamide in 21 different NADES compositions comprising choline chloride with sugars or sugar alcohols was measured spectrophotometrically. Thermodynamic parameters describing the studied systems were determined using the COSMO-RS computational protocol. Results: All of the considered NADES compositions gave an increase in solubility of the studied sulfonamides, with the highest solubilities obtained for the system comprising choline chloride and glycerol in unimolar proportions, which gave a solubility advantage of 83.7 and 73.8 for sulfanilamide and sulfacetamide, respectively. Theoretical studies indicated that the dissolution of both considered sulfonamides has a low endothermic character, with the lowest enthalpy values obtained for the most optimal, i.e. unimolar, proportions. The non-monotonous trend of enthalpy of dissolution was also discussed in terms of intermolecular interactions. Conclusions: The obtained results show the feasibility of using NADES as solubility enhancers for sulfonamides and encourage for further exploration in this field.

Effect of polymer type on characteristics of buccal tablets using factorial design

A two factor three level factorial design was used to investigate the effects of carbopol and cationic hydrophilic polymers which have a common use in buccal drug formulations. Statistical models with interaction terms were derived to evaluate influence of carbopol (X1) and chitosan (X2) on tablet disintegration (Y1) and dissolution (Y2), mechanical properties (Y3), swelling (Y4). Tablet disintegration studies were carried out using two different pH environments within buccal region pH limits and also two different commonly used dissolution methods for buccal tablets were also investigated to compare the effect of polymer type on dissolution. Polymer type and ratio affect the characteristics of the buccal tablets due to their different physicochemical behavior at buccal pH. Also significant variances between dissolution profiles for buccal tablets, using either USP Paddle or flow through cell methods were found. These results indicate that both polymer type and ratio as well as combination of them effects the drug behavior in different ways.

Influence of pH Modulation on Dynamic Behavior of Gel Layer and Release of Weakly Basic Drug from HPMC/Wax Matrices, Controlled by Acidic Modifiers Evaluated by Multivariate Data Analysis

The solubility of weakly basic drugs in passage through gastrointestinal tract leads to their pH-dependent release from extended release formulations and to lower drug absorption and bioavailability. The aim of this study was to modulate the micro-environmental pH of hypromellose/montanglycol wax matrices and to observe its influence on the release of weakly basic drug verapamil hydrochloride (VH) with a pH-dependent solubility with respect to gel layer formation and its dynamics. For this study, malic and succinic acids differing in their solubility and pKa were selected as pH modifiers. The dissolution studies were performed by the method of changing pH. Within the same conditions, pH, thickness, and penetration force of the gel layer were measured as well. From the PCA sub-model, it is evident that a higher acid concentration ensured lower gel pH and conditions for higher drug solubility, thus creating larger gel layer with smaller rigidity, resulting in higher VH release during the dissolution test. Incorporation of stronger and more soluble malic acid (100 mg/tablet) created the most acidic and the thickest gel layer through which a total of 74% of VH was released. Despite having lower strength and solubility, matrices containing succinic acid (100 mg/tablet) released a comparable 71% of VH in a manner close to zero-order kinetics. The thinner and less rigid gel layers of the succinic acid matrices allowed an even slightly faster VH release at pH 6.8 than from matrices containing malic acid. Thus acid solubility is more parametrically significant than acid pKa for drug release at pH 6.8.

Effects of Manufacturing Methods on Dissolution and Absorption of Ketoconazole in the Presence of Organic Acid as a pH Modifier

Poorly water-soluble compounds have a potential risk of low and variable bioavailability caused by incomplete dissolution. Incorporation of organic acids as pH modifiers is effective method for solubility enhancement of basic compounds and requires no special technique and equipment. The purpose of this study was to evaluate the effect of manufacturing method on the extent of drug solubility enhancement. We successfully prepared the granules and tablets containing ketoconazole (KZ), which is weakly basic, as a model compound and citric acid as a pH modifier using conventional wet and dry granulations. KZ solubility under non-sink condition was enhanced with supersaturation using both wet and dry granulations. High-shear granulation was the most effective method in terms of KZ dissolution enhancement, because both an intimate contact and strong bonding between KZ and incorporated acid were achieved. KZ dissolved amount from the granules prepared by high-shear granulation was about eight times higher than that from the granules without the acid. The granulation involved to suppress a diffusion of acid dissolved, leading to the effectively maintained supersaturation state. The bioavailability of KZ after oral administration to rats was improved by applying high-shear granulation with citric acid independent of gastrointestinal pH. The granules prepared by high-shear granulation showed the bioavailability about 1.7-fold higher than that of the physical mixture in rats with and without neutralization of stomach. As a result, both the dissolution and absorption rates of KZ after oral administration were enhanced using conventional manufacturing technology.

Extended release of flurbiprofen from tromethamine-buffered HPMC hydrophilic matrix tablets

The pH-dependent solubility of a drug can lead to pH-dependent drug release from hydrophilic matrix tablets. Adding buffer salts to the formulation to attempt to mitigate this can impair matrix hydration and negatively impact drug release. An evaluation of the buffering of hydrophilic matrix tablets containing a pH-dependent solubility weak acid drug (flurbiprofen), identified as possessing a deleterious effect on hydroxypropyl methylcellulose (HPMC) solubility, swelling and gelation, with respect to drug dissolution and the characteristics of the hydrophilic matrix gel layer in the presence of tromethamine as a buffer was undertaken. The inclusion of tromethamine as an alkalizing agent afforded pH-independent flurbiprofen release from matrices based on both HPMC 2910 (E series) and 2208 (K series), while concomitantly decreasing the apparent critical effect on dissolution mediated by this drug with respect to the early pseudo-gel layer formation and functionality. Drug release profiles were unaffected by matrix pH-changes resulting from loss of tromethamine over time, suggesting that HPMC inhibited precipitation of drug from supersaturated solution in the hydrated matrix. We propose that facilitation of diffusion-based release of potentially deleterious drugs in hydrophilic matrices may be achieved through judicious selection of a buffering species.

Surface-Deacetylated Chitin Nano-Fiber/Hyaluronic Acid Composites as Potential Antioxidative Compounds for Use in Extended-Release Matrix Tablets

In this study, we examined a possible use of a surface-deacetylated chitin nano-fiber (SDCH-NF) and hyaluronic acid (HA) interpolymer complex (IPC) tablet as a potential antioxidative compound in extended-release matrix tablets. The antioxidant properties of untreated chitin (UCH), SDCH-NF, and HA were examined using N-centered radicals derived from 1,1'-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). SDCH-NF and HA had acceptable scavenging abilities and were relatively efficient radical scavengers, but UCH was much less effective. The results suggest that SDCH-NF and HA could serve as scavengers of compounds related to the development of oxidative stress. An SDCH-NF/HA IPC tablet was prepared and evaluated as an extended-release tablet matrix using famotidine (FMT) as a model drug. The release of FMT from the IPC tablet (DCF-NF:HA=1:1) was slower than that from a SDCH-NF only tablet. Turbidity measurements and X-ray diffraction (XRD) data also indicated that the optimum complexation ratio for IPC between SDCH-NF/HA is 1/1, resulting in a good relationship between turbidity or XRD of the complex and the release ratio of FMT. These results suggest that an SDCH-NF/HA tablet has the potential for use in an extended-release IPC tablet with a high antioxidant activity.

Enhanced bioavailability of a poorly water-soluble weakly basic compound using a combination approach of solubilization agents and precipitation inhibitors: a case study

Poorly water-soluble weakly basic compounds which are solubilized in gastric fluid are likely to precipitate after the solution empties from the stomach into the small intestine, leading to a low oral bioavailability. In this study, we reported an approach of combining solubilization agents and precipitation inhibitors to produce a supersaturated drug concentration and to prolong such a drug concentration for an extended period of time for an optimal absorption, thereby improving oral bioavailability of poorly water-soluble drugs. A weakly basic compound from Johnson and Johnson Pharmaceutical Research and Development was used as a model compound. A parallel microscreening precipitation method using 96-well plates and a TECAN robot was used to assess the precipitation of the tested compound in the simulated gastric fluid (SGF) and the simulated intestinal fluid (SIF), respectively, for lead solubilizing agents and precipitation inhibitors. The precipitation screening results showed vitamin E TPGS was an effective solubilizing agent and Pluronic F127 was a potent precipitation inhibitor for the tested compound. Interestingly, the combination of Pluronic F127 with vitamin E TPGS resulted in a synergistic effect in prolonging compound concentration upon dilution in SIF. In addition, HPMC E5 and Eudragit L100-55 were found to be effective precipitation inhibitors for the tested compounds in SGF. Furthermore, optimization DOE study results suggested a formulation sweet spot comprising HPMC, Eudragit L 100-55, vitamin E TPGS, and Pluronic F127. The lead formulation maintained the tested compound concentration at 300 μg/mL upon dilution in SIF, and more than 70% of the compound remained solubilized compared with the compound alone at <1 μg/mL of its concentration. Dosing of the solid dosage form predissolved in SGF in dogs resulted in 52% of oral bioavailability compared to 26% for the suspension control, a statistically significant increase (p = 0.002). The enhanced oral bioavailability of the tested compound could be attributed to generation and prolongation of a supersaturated drug concentration in vivo by the solubilizing agents and precipitation inhibitors. The study demonstrates that the combination approach of solubilization agents and precipitation inhibitors provides improved oral bioavailability for a poorly water-soluble weakly basic compound.

Potent dried drug nanosuspensions for oral bioavailability enhancement of poorly soluble drugs with pH-dependent solubility

The objective of this study was to enhance the oral bioavailability of itraconazole (ITZ) with dried drug nanosuspensions. The feasibility of using poloxamer 407 or HPMC (50 cp) as stabilizers for preparing ITZ nanosuspensions by facile acid-base neutralization was investigated. Dried ITZ nanosuspensions were prepared by spray drying. The effect of matrix former on the dissolution rate of dried ITZ nanosuspensions was investigated. Results from dissolution test revealed that spray-dried ITZ nanosuspensions (ITZ:HPMC:mannitol 1:0.5:2, w/w) preserved the high dissolution rate from nanosuspensions. After oral administration in rats, the AUC(0-36) from dried ITZ nanosuspensions was 1.5-fold and 1.8-fold higher than the AUC(0-36) from sporanox pellets (commercial product) in the fed and fasted states, respectively (p<0.05). More importantly, the AUC(0-36) from dried ITZ nanosuspensions showed no difference between fed/fasted states, because this formulation could enhance the adsorption of ITZ in target site (small intestine) regardless of food intake. In addition, dried ITZ nanosuspensions showed a lower inter-individual variability in terms of bioavailability. Positive results demonstrate that dried drug nanosuspensions formulation prepared by acid-base neutralization combined with spray drying may be a promising method for enhancing the oral bioavailability of poorly soluble drugs with pH-dependent solubility.

Design and mechanism of on-off pulsed drug release using nonenteric polymeric systems via pH modulation

The aim was to design a pH-sensitive pulsatile drug delivery system that allows for an on-off pulsed release of a drug using polyacrylic acid (PAA) blended with ethyl cellulose (EC) in different ratios. PAA, a polyelectrolyte polymer, exhibits a highly coiled conformation at low pH but a highly extended structure at high pH. Fumaric acid, which is an internal acidifying agent, was incorporated into the hydroxypropyl methylcellulose-based core tablets to create an acidic microenvironmental pH (pH(M)). The concentration of fumaric acid inside the core tablet and the ratio of PAA/EC in the coating layer were very crucial in modulating drug release behaviors. When the fumaric acid was retained in the core tablet, it gave a more acidic pH(M), so that the PAA was kept in a highly coiled state in the coated film, which hindered drug release ("off" release pattern). Interestingly, the release profiles of the drug and fumaric acid from coated tablets showed the on-off pulsed pattern upon dissolution. Imaging analyses using scanning electron microscopy, near-infrared imaging, confocal laser scanning microscopy, and Fourier transform infrared spectroscopy confirmed this on-off release behavior of the drug and fumaric acid from coated tablets.

Useful Extend-release Chitosan Tablets with High Antioxidant Activity

The antioxidant properties of different low molecular weight (LMW) chitosans (CS1; 22 kDa, CS2; 38 kDa, CS3; 52 kDa, CS4; 81 kDa) were examined for possible use in extended-release tablets. The criteria used were the ability of the chitosans to reduce Cu2+, and hydroxyl and superoxide radicals and N-centered radicals derived from 1,1'-diphenyl-2-picrylhydrazyl, via the use of ESR spectrometry. CS2 showed the highest scavenging activity. CS1 and CS3, however, were much less effective and CS4 was not a viable antioxidant. The results suggest that CS2 could be useful in combating the development of oxidative stress. A series of chitosan tablets were prepared using a spray drying method and evaluated as an extended-release matrix tablet using theophylline (TPH) as a model drug. The release of TPH from the different MW chitosan tablets increased with increasing MW of the chitosan used. CS2, CS3 and CS4 showed a reasonable release activity, but CS1 showed the shortest release activity. Moreover, the CS2-TPH tablet showed the highest scavenging activity of the three chitosan tablets (CS2-CS4) using 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) radicals. These results suggest that a CS2-TPH tablet could be potentially useful in an extended-release matrix tablet with a high antioxidant activity.

Effects of thermal curing conditions on drug release from polyvinyl acetate-polyvinyl pyrrolidone matrices

This study aimed to investigate the effects of dry and humid heat curing on the physical and drug release properties of polyvinyl acetate-polyvinyl pyrrolidone matrices. Both conditions resulted in increased tablet hardness; tablets stored under humid conditions showed high plasticity and deformed during hardness testing. Release from the matrices was dependent on the filler's type and level. Release profiles showed significant changes, as a result of exposure to thermal stress, none of the fillers used stabilized matrices against these changes. Density of neat polymeric compacts increased upon exposure to heat; the effect of humid heat was more evident than dry heat. Thermograms of samples cured under dry heat did not show changes, while those of samples stored under high humidity showed significant enlargement of the dehydration endotherm masking the glass transition of polyvinyl acetate. The change of the physical and release properties of matrices could be explained by the hygroscopic nature of polyvinyl pyrrolidone causing water uptake; absorbed water then acts as a plasticizer of polyvinyl acetate promoting plastic flow, deformation, and coalescence of particles, and altering the matrices internal structure. Results suggest that humid heat is more effective as a curing environment than dry heat for polyvinyl acetate-polyvinyl pyrrolidone matrices.

Evaluation of diclofenac sodium release from matrix pellets compressed into MUPS tablets

The purpose of the study was to screen the effects of formulation factors on the in vitro release profile of diclofenac sodium from matrix pellets compressed into multiple unit pellet system (MUPS) tablets using design of experiment (DOE). Extended release of diclofenac sodium was accomplished using Carbopol 71G as matrix substance. According to Fractional Factorial Design FFD 2(3-1) four formulations of diclofenac sodium MUPS matrix tablets were prepared. The process of direct pelletization and subsequently compression of the pellets into tablets was applied in order to investigate a different approach in formulation of matrix systems and to achieve a better control of the process factors over the principal response - the release of the drug. The investigated factors were X1-the percentage of polymer Carbopol 71G, X2-crushing strength of the tablet and X3-different batches of the diclofenac sodium. In vitro dissolution time profiles at 6 different sampling times were chosen as responses. Results of drug release studies indicated that drug release rates vary between different formulations, with a range of 1 to 8 h to complete dissolution. The most important impact on the drug release had factor X1-the percentage of polymer Carbopol 71G. The polymer percentage is suggested as release regulator for diclofenac sodium release from MUPS matrix tablets. All other investigated factors had no significant influence on the release profile of diclofenac sodium.

Development of a Multiple Unit Pellet Formulation for a Weakly Basic Drug

SAG/ZK [3-(5-Chloro-2-[2-[(2R)-4-(4-fluorobenzyl)-2-methylpiperazin-1-yl]-2-oxoethoxy]phenyl)uronium hydrogen sulfate], a potent candidate for the oral treatment of inflammatory diseases, demonstrated pH-dependent solubility. Drug release from conventional pellet formulations decreased with increasing pH values of the dissolution medium. The aim of this study was to overcome this problem and to achieve pH-independent drug release. Extended release pellets were prepared by extrusion/spheronization followed by film coating with an aqueous polyvinylacetate/polyvinylpyrrolidone dispersion. To overcome the problem of pH-dependent drug release organic acids such as fumaric, tartaric, and adipic acid were incorporated into the core pellets. X-ray diffraction studies were done in order to investigate potential recrystallization and formation of different salts of SAG/ZK. The addition of fumaric acid was found to lower the pH values within the core pellets during the release of SAG/ZK in phosphate buffer pH 6.8. Therefore, increased release rates at higher pH values were observed thus leading to pH-independent drug release. In contrast, drug release remained pH-dependent for pellets containing tartaric and adipic acid, which can be explained with the lower acidic strength and higher aqueous solubility of these acids. X-ray diffraction studies showed no recrystallization and formation of salts of active ingredient and organic acid.

Effect of a pharmaceutical cationic exchange resin on the properties of controlled release diphenhydramine hydrochloride matrices using Methocel K4M or Ethocel 7cP as matrix formers

This work was aimed at evaluating the effect of a pharmaceutical cationic exchange resin (Amberlite IRP-69) on the properties of controlled release matrices using Methocel K4M (HPMC) or Ethocel 7cP (EC) as matrix formers. Diphenhydramine hydrochloride (DPH), which was cationic and water soluble, was chosen as a model drug. HPMC- and EC-based matrices with varying amounts (0-40%w/w) of resin incorporation were prepared by a direct compression. Matrix properties including diameter, thickness, hardness, friability, surface morphology and drug release were evaluated. The obtained matrices were comparable in diameter and thickness regardless of the amount of resin incorporation. Increasing the incorporated resin decreased the hardness of HPMC- and EC-based matrices, correlating with the degree of rupturing on the matrix surfaces. The friability of HPMC-based matrices increased with increasing the incorporated resin, corresponding to their decreased hardness. In contrast, the EC-based matrices showed no significant change in friability in spite of decreasing hardness. The incorporated resin differently influenced DPH release from HPMC- and EC-based matrices in deionized water. The resin further retarded DPH release from HPMC-based matrices due to the gelling property of HPMC and the ion exchange property of the resin. In contrast, the release from EC-based matrices initially increased because of the disintegrating property of the resin, but thereafter declined due to the complex formation between released drug and dispersed resin via the ion exchange process. The release in ionic solutions was also described. In conclusion, the incorporated resin could alter the release and physical properties of matrices.

Development of a novel osmotically driven drug delivery system for weakly basic drugs

The drug substance SAG/ZK has a short biological half-life and because of its weakly basic nature a strong pH-dependent solubility was observed. The aim of this study was to develop a controlled release (cr) multiple unit pellet formulation for SAG/ZK with pH-independent drug release. Pellets with a drug load of 60% were prepared by extrusion/spheronization followed by cr-film coating with an extended release polyvinyl acetate/polyvinyl pyrrolidone dispersion (Kollidon SR 30 D). To overcome the problem of pH-dependent drug release the pellets were then coated with a second layer of an enteric methacrylic acid and ethyl acrylate copolymer (Kollicoat MAE 30 DP). To increase the drug release rates from the double layered cr-pellets different osmotically active ionic (sodium and potassium chloride) and nonionic (sucrose) additives were incorporated into the pellet core. Drug release studies were performed in media of different osmotic pressure to clarify the main release mechanism. Extended release coated pellets of SAG/ZK demonstrated pH-dependent drug release. Applying a second enteric coat on top of the extended release film coat failed in order to achieve pH-independent drug release. Already low enteric polymer levels on top of the extended release coated pellets decreased drug release rates at pH 1 drastically, thus resulting in a reversal of the pH-dependency (faster release at pH 6.8 than in 0.1N HCl). The addition of osmotically active ingredients (sodium and potassium chloride, and sucrose) increased the imbibing of aqueous fluids into the pellet cores thus providing a saturated drug solution inside the beads and increasing drug concentration gradients. In addition, for these pellets increased formation of pores and cracks in the polymer coating was observed. Hence drug release rates from double layered beads increased significantly. Therefore, pH-independent osmotically driven SAG/ZK release was achieved from pellets containing osmotically active ingredients and coated with an extended and enteric polymer. In contrast, with increasing osmotic pressure of the dissolution medium the in vitro drug release rates decreased significantly.

Preparation of an extended-release matrix tablet using chitosan/Carbopol interpolymer complex

A chitosan and Carbopol interpolymer complex (IPC) was formed using a precipitation method in an acidic solution. The chitosan and Carbopol IPC was characterized by Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and turbidity measurements. FT-IR demonstrated that the IPC formed a complex through an electrostatic interaction between the protonated amine (NH(3)(+)) group of chitosan and the carboxylate (COO(-)) group of Carbopol. DSC indicated the IPC to have different thermal characteristics from chitosan or Carbopol. The turbidity measurement revealed the complexation ratio of IPC between chitosan/Carbopol to be 1/4. A theophylline tablet was prepared using the IPC as a matrix material. The drug release profile from this tablet was similar to that from the HPMC tablet and showed a pH-independent release profile. The mechanisms for drug release from the IPC tablet were diffusional release at pH 6.8 and relaxational release at pH 1.2.

pH-independent drug release of an extremely poorly soluble weakly acidic drug from multiparticulate extended release formulations

Extended release mini matrix tablets for 8-Prenylnaringenin (8-PN), an extremely poorly soluble weakly acidic drug, were developed by using polyvinylacetate/polyvinylpyrrolidone as matrix former. Mini matrix tablets were manufactured by direct compression or wet granulation technique. With conventional modified release formulations, the drug demonstrated pH-dependent release due to pH-dependent solubility of the drug substance (i.e., increasing solubility at higher pH-values). In order to achieve pH-independent drug release two classes of pH-modifying agents (water-soluble vs. water-insoluble) were studied with respect to their effect on the dissolution of 8-PN. Addition of water-soluble salts of weak acids (sodium carbonate and sodium citrate) failed in order to achieve pH-independent 8-PN release. In contrast, addition of water insoluble salts of a strong base (magnesium hydroxide and magnesium oxide) was found to maintain high pH-values within the mini matrix tablets during release of 8-PN at pH 1 over a period of 10 h. The micro-environmental conditions for the dissolution of the weakly acidic drug were kept almost constant, thus resulting in pH-independent drug release. Compound release from mini matrix tablets prepared by wet granulation was faster compared to the drug release from tablets prepared by direct compression.