Properties of tablets containing granulations of ibuprofen and an acrylic copolymer prepared by thermal processes

The Use of Hot Melt Extrusion to Prepare a Solid Dispersion of Ibuprofen in a Polymer Matrix

In this work, we report the use of the hot melt extrusion method in harsh extrusion conditions, i.e., screw rotation speed of 250 rpm, temperature above 100 °C, and two mixing zones, in order to obtain an amorphous dispersion of an active pharmaceutical ingredient (API) that is sparingly soluble in water. As a polymer matrix Eudragit EPO (E-EPO) and as an API ibuprofen (IBU) were used in the research. In addition, the plasticizer Compritol 888 ATO (COM) was tested as a factor potentially improving processing parameters and modifying the IBU release profile. In studies, 25% by weight of IBU, 10% of COM and various extrusion temperatures, i.e., 90, 100, 120, 130, and 140 °C, were used. Hot melt extrusion (HME) temperatures were selected based on the glass transition temperature of the polymer matrix (T_g = 42 °C) and the melting points of IBU (T_m = 76 °C) and COM (T_m = 73 °C), which were tested by differential scanning calorimetry (DSC). The thermal stability of the tested compounds, determined on the basis of measurements carried out by thermogravimetric analysis (TGA), was also taken into account. HME resulted in amorphous E-EPO/IBU solid dispersions and solid dispersions containing a partially crystalline plasticizer in the case of E-EPO/IBU/COM extrudates. Interactions between the components of the extrudate were also studied using infrared spectroscopy (FTIR-ATR). The occurrence of such interactions in the studied system, which improve the stability of the obtained solid polymer dispersions, was confirmed. On the basis of DSC thermograms and XRPD diffractograms, it was found that amorphous solid dispersions were obtained. In addition, their stability was confirmed in accelerated conditions (40 °C, 75% RH) for 28 days and 3 months. The release profiles of prepared tablets showed the release of 40% to 63% of IBU from the tablets within 180 min in artificial gastric juice solution, with the best results obtained for tablets with E-EPO/IBU extrudate prepared at a processing temperature of 140 °C.

Novel Glyceryl Monostearate- and Polyethylene Glycol 6000-Based Ibuprofen Pellets Prepared by Hot-Melt Extrusion: Evaluation and Stability Assessment

Purpose

To prepare stable sustained-release (SR) pellets, containing high ibuprofen (IBU) loading, by hot-melt extrusion (HME) technique using polyethylene glycol 6000 (PEG 6000) and glyceryl monostearate (GMS).

Methods

HME pellets (60% w/w IBU) were prepared using PEG 6000, GMS, and mixture of both polymers (1:1). Stability studies were performed under stress conditions (40 °C and relative humidity “RH” of 75%) for 6 months and at room temperature for 12 months. Fresh and stored IBU pellets were evaluated by drug content (HPLC), release rate study (USP apparatus IV), DSC, and XRD.

Results

HME succeeded to produce SR-IBU pellets with high drug loading. PEG 6000 gave higher IBU release rate and relatively unstable formula after storage. PEG 6000/GMS mixture gave prolonged IBU release up to 4 h with stable formula for 12 months at room temperature. While, IBU/GMS pellets gave SR profile up to 6 h and a stable formula under both testing conditions. These advantages of IBU/GMS pellets could be an excellent candidate for SR-IBU product. DSC and XRD analysis data (enthalpy and counts) for IBU and polymers gave a mirror image for IBU release profiles of the studied HME pellets, for both fresh and stored samples.

Conclusion

Stable SR-IBU/GMS HME pellets with high IBU loading (60% w/w) were successfully produced, for the first time, without any other excipients.

The use of rheology to elucidate the granulation mechanisms of a miscible and immiscible system during continuous twin-screw melt granulation

Twin-screw hot melt granulation (TS HMG) is a valuable, but still unexplored alternative to granulate temperature and moisture sensitive drugs in a continuous way. Recently, the material behavior of an immiscible drug-binder blend during TS HMG was unraveled by using a rheometer and differential scanning calorimetry (DSC). Additionally, vibrational spectroscopic techniques proved the link between TS HMG and rheology since equal interactions at molecular level did occur in both processes. This allowed to use a rheometer to gain knowledge of the material behavior during hot melt processing of an immiscible drug-binder blend. However, miscibility of a drug-binder formulation and drug-binder interactions appear to influence the rheological properties and, hence conceivably also the granulation mechanism. The aim of this research was to examine if the TS HMG process of a miscible formulation system is comparable with the mechanism of an immiscible system and to evaluate whether rheology still serves as a useful tool to understand and optimize the hot melt granulation (HMG) process. The executed research (thermal analysis, rheological parameters and spectroscopic data) demonstrated the occurrence of a high and broad tan(δ) curve without a loss peak during the rheological temperature ramp which implies a higher material deformability without movement of the softened single polymer chains. Spectroscopic analysis revealed drug-polymer interactions which constrain the polymer to flow independently. As a result, the binder distribution step, which generally follows the immersion step, was hindered. This insight assisted the understanding of the granule properties. Inhomogeneous granules were produced due to large initial nuclei or adhesion of multiple smaller nuclei. Consequently, a higher granulation temperature was required in order to get the binder more homogeneously distributed within the granules.

A quality by design approach to understand formulation and process variability in pharmaceutical melt extrusion processes

Objectives

In this study, the principles of quality by design (QbD) have been uniquely applied to a pharmaceutical melt extrusion process for an immediate release formulation with a low melting model drug, ibuprofen.

Methods

Two qualitative risk assessment tools – Fishbone diagram and failure mode effect analysis – were utilized to strategically narrow down the most influential parameters. Selected variables were further assessed using a Plackett-Burman screening study, which was upgraded to a response surface design consisting of the critical factors to study the interactions between the study variables. In process torque, glass transition temperature (Tg) of the extrudates, assay, dissolution and phase change were measured as responses to evaluate the critical quality attributes (CQAs) of the extrudates. The effect of each study variable on the measured responses was analysed using multiple regression for the screening design and partial least squares for the optimization design.

Key findings

Experimental limits for formulation and process parameters to attain optimum processing have been outlined. A design space plot describing the domain of experimental variables within which the CQAs remained unchanged was developed.

Conclusions

A comprehensive approach for melt extrusion product development based on the QbD methodology has been demonstrated. Drug loading concentrations between 40- 48%w/w and extrusion temperature in the range of 90–130°C were found to be the most optimum.

Interactions between drugs and polymers influencing hot melt extrusion

Objectives

Hot melt extrusion (HME) as a technique for producing amorphous solid dispersion (ASD) has been widely used in pharmaceutical research. The biggest challenge for the application of HME is the thermal degradation of drug, poor physical stability of ASD and precipitation of drug during dissolution. Interactions between drugs and polymers may play an important role in overcoming these barriers. In this review, influence of drug–polymer interactions on HME and the methods for characterizing the drug–polymer interactions were reviewed.

Key findings

Strong drug–polymer interactions, especially ionic interactions and hydrogen bonds, are helpful to improving the thermal stability of drug during HME, enhancing the physical stability of ASD during storage and maintaining supersaturated solution after dissolution in gastrointestinal tract. The interactions can be quantitatively and qualitatively characterized by many analysing methods.

Conclusions

As many factors collectively determine the properties of HME products, drug–polymer interactions play an extremely important role. However, the action mechanisms of drug–polymer interactions need intensive investigation to provide more useful information for optimizing the formulation and the process parameters of HME.

Sustained release tablets containing soluble polymethacrylates: comparison with tableted polymethacrylate IPEC polymers

The objective of this study was to compare a novel sustained release tablet formulation that has the potential to be used for drugs of different physicochemical properties using a binary mixture of polymethacrylate polymers in their salt forms with the polymethacrylate interpolyelectrolyte complex (IPEC) tablets in terms of drug release and compactness. Also, we aimed to compare this formulation with an IPEC tablet in terms of drug release. Tablets prepared using Eudragit E-Citrate and Eudragit L-Sodium were more convenient, easier to prepare, and showed better sustained release and compactness characteristics compared to IPEC tablets of similar concentrations and preparation methods.

Applications of hot-melt extrusion for drug delivery

In today's pharmaceutical arena, it is estimated that more than 40% of new chemical entities produced during drug discovery efforts exhibit poor solubility characteristics. However, over the last decade hot-melt extrusion (HME) has emerged as a powerful processing technology for drug delivery and has opened the door to a host of molecules previously considered unviable as drugs. HME is considered to be an efficient technique in developing solid molecular dispersions and has been demonstrated to provide sustained, modified and targeted drug delivery resulting in improved bioavailability. This article reviews the range of HME applications for pharmaceutical dosage forms, such as tablets, capsules, films and implants for drug delivery through oral, transdermal, transmucosal, transungual, as well as other routes of administration. Interest in HME as a pharmaceutical process continues to grow and the potential of automation and reduction of capital investment and labor costs have made this technique worthy of consideration as a drug delivery solution.

Physicochemical properties of film-coated melt-extruded pellets

The purpose of this study was to investigate the physicochemical properties of poly(ethylene oxide) (PEO) and guaifenesin containing beads prepared by a melt-extrusion process and film-coated with a methacrylic acid copolymer. Solubility parameter calculations, thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), modulated differential scanning calorimetry (MDSC), X-ray powder diffraction (XRPD) and high performance liquid chromatography (HPLC) were used to determine drug/polymer miscibility and/or the thermal processibility of the systems. Powder blends of guaifenesin, PEO and functional excipients were processed using a melt-extrusion and spheronization technique and then film-coated in a fluidized bed apparatus. Solubility parameter calculations were used to predict miscibility between PEO and guaifenesin, and miscibility was confirmed by SEM and observation of a single melting point for extruded drug/polymer blends during MDSC investigations. The drug was stable following melt-extrusion as determined by TGA and HPLC; however, drug release rate from pellets decreased upon storage in sealed HDPE containers with silica desiccants at 40 degrees C/75% RH. The weight loss on drying, porosity and tortuosity determinations were not influenced by storage. Recrystallization of guaifenesin and PEO was confirmed by SEM and XRPD. Additionally, the pellets exhibited a change in adhesion behaviour during dissolution testing. The addition of ethylcellulose to the extruded powder blend decreased and stabilized the drug release rate from the thermally processed pellets. The current study also demonstrated film-coating to be an efficient process for providing melt-extruded beads with pH-dependent drug release properties that were stable upon storage at accelerated conditions.

The Influence of Thermal Treatment on the Release Behavior of Diclofenac Sodium from Acrylic Matrices

The objective of this work was to investigate the effect of thermal treating on the release rate of diclofenac sodium from Eudragit RS and Eudragit RL matrices. Eudragit RS and RL are nonswelling polymers that have a low glass transition (Tg) temperature. The matrices were thermally treated at different temperatures (40, 50, 60, and 70 degrees C) for different periods of times (2, 5, and 24 h). The results showed that thermal treating at temperatures less than the Tg of the polymer has no effect on the release of the drug, whereas heat-treating at temperatures higher than the Tg decreases the release rate of diclofenac sodium from matrices. It was shown that the duration of heat treatment was also an important factor in controlling the release rate of diclofenac sodium from Eudragit matrices. The results showed that an increase in the duration of heat treatment from 2 h to 24 h resulted in a reduction in the release rate of the drug. Scanning electron microscopy of the cross section of the tablet before and after heat treating showed that the tablets were deformed and fused into a continuous and homogeneous structure after heat treating. Thermally treated tablets demonstrated fewer surface defects than did nonthermally treated tablets. These structural changes in the tablet compacts resulted in a matrix structure that decreased the release rate of the diclofenac sodium from Eudragit matrices.

Pharmaceutical Applications of Hot-Melt Extrusion: Part I

Interest in hot-melt extrusion techniques for pharmaceutical applications is growing rapidly with well over 100 papers published in the pharmaceutical scientific literature in the last 12 years. Hot-melt extrusion (HME) has been a widely applied technique in the plastics industry and has been demonstrated recently to be a viable method to prepare several types of dosage forms and drug delivery systems. Hot-melt extruded dosage forms are complex mixtures of active medicaments, functional excipients, and processing aids. HME also offers several advantages over traditional pharmaceutical processing techniques including the absence of solvents, few processing steps, continuous operation, and the possibility of the formation of solid dispersions and improved bioavailability. This article, Part I, reviews the pharmaceutical applications of hot-melt extrusion, including equipment, principles of operation, and process technology. The raw materials processed using this technique are also detailed and the physicochemical properties of the resultant dosage forms are described. Part II of this review will focus on various applications of HME in drug delivery such as granules, pellets, immediate and modified release tablets, transmucosal and transdermal systems, and implants.

Ultrasound transmission technique as a potential tool for physical evaluation of monolithic matrix tablets

The aim of this study was to investigate the effects of tablet porosity and particle size fraction of compacted Starch acetate powders, with and without model drug caffeine, on acoustic properties of tablets. The ultrasound velocity was determined from the transmission measurements. Tablets of starch acetate (SA DS 2.7) powder with two particle size fractions of 0-53 and 0-710 microm were compressed with a compaction simulator. Porosities of tablets varied in the range from 12% to 43% for both particle size fractions. Strong associations were found between the ultrasound velocity and physical properties of the tablets such as porosity and particle size fraction. Interestingly, ultrasound velocity was practically insensitive to inclusion of the model drug caffeine with the concentrations used. Based on this study ultrasound transmission method is a potential non-destructive tool for studying structural changes of tablets and other solid dosage forms.

Properties of sustained release hot-melt extruded tablets containing chitosan and xanthan gum

The aim of this study was to investigate the influence of pH, buffer species and ionic strength on the release mechanism of chlorpheniramine maleate (CPM) from matrix tablets containing chitosan and xanthan gum prepared by a hot-melt extrusion process. Drug release from hot-melt extruded (HME) tablets containing either chitosan or xanthan gum was pH and buffer species dependent and the release mechanisms were controlled by the solubility and ionic properties of the polymers. All directly compressed (DC) tablets prepared in this study also exhibited pH and buffer species dependent release. In contrast, the HME tablets containing both chitosan and xanthan gum exhibited pH and buffer species independent sustained release. When placed in 0.1N HCl, the HME tablets formed a hydrogel that functioned to retard drug release in subsequent pH 6.8 and 7.4 phosphate buffers even when media contained high ionic strength, whereas tablets without chitosan did not form a hydrogel to retard drug release in 0.1N HCl. The HME tablets containing both chitosan and xanthan gum showed no significant change in drug release rate when stored at 40 degrees C for 1 month, 40 degrees C and 75% relative humidity (40 degrees C/75% RH) for 1 month, and 60 degrees C for 15 days.

Physicochemical characterization and mechanisms of release of theophylline from melt-extruded dosage forms based on a methacrylic acid copolymer

The purpose of the current study was to investigate the physicochemical properties of melt-extruded dosage forms based on Acryl-EZE and to determine the influence of gelling agents on the mechanisms and kinetics of drug release from thermally processed matrices. Acryl-EZE is a pre-mixed excipient blend based on a methacrylic acid copolymer that is optimized for film-coating applications. Powder blends containing theophylline, Acryl-EZE, triethyl citrate and an optional gelling agent, Methocel K4M Premium (hydroxypropyl methylcellulose, HPMC, hypromellose 2208) or Carbopol 974P (carbomer), were thermally processed using a Randcastle single-screw extruder. The physical and chemical stability of materials during processing was determined using thermal gravimetric analysis and HPLC. The mechanism of drug release was determined using the Korsmeyer-Peppas model and the hydration and erosion of tablets during the dissolution studies were investigated. The excipient blends were physically and chemically stable during processing, and the resulting dosage forms exhibited pH-dependent dissolution properties. Extrusion of blends containing HPMC or carbomer changed the mechanism and kinetics of drug release from the thermally processed dosage forms. At concentrations of 5% or below, carbomer was more effective than HPMC at extending the duration of theophylline release from matrix tablets. Furthermore, carbomer containing tablets were stable upon storage for 3 months at 40 degrees C/75% RH. Thus, hot-melt extrusion was an effective process for the preparation of controlled release matrix systems based on Acryl-EZE.

Mechanistic evaluation of the effect of thermal-treating on Eudragit RS matrices

Thermal treatment of acrylic matrices was recently introduced as a tool for prolonging the release of drug. Thermal treatment at temperatures above the T(g) of the polymer can decrease drug release rate. In this research we studied the mechanism of the effect of thermal treatment on Eudragit RS matrices. Indomethacin was used as model drug. The results showed that polymer chain movement and redistribution of the polymer in the tablet matrix structure after thermal-treating is the possible mechanism of drug release prolongation. The melting and resolidification of the polymer, due to the thermal treatment has apparently resulted in a redistribution of the polymer throughout the matrix and a change in the porosity of the tablet. FTIR results did not show any drug-polymer interaction due to heat-treatment. DSC and PXD studies ruled out the occurrence of solid solution and polymorphic change of the drug.

Characterization of the Mechanism of Interaction in Ibuprofen‐Eudragit RL100® Coevaporates

The present study is a preliminary exploration of the affinity between a carboxylic model drug, the nonsteroidal antiinflammatory agent ibuprofen (IBU) and Eudragit RL100 (RL) polymer. Due to the presence of a variable amount of quaternary ammonium groups in this matrix, physical and chemical interaction with the carboxylic drug can occur, which reinforces its scant mechanical dispersion in the polymer network and can ultimately affect its release profile in vitro and in vivo. To study these aspects, IBU was mixed at increasing weight ratios and in different chemical forms (free acid, sodium salt, and n-butyl ester), to investigate further the role of the carboxylic group in the interaction with the RL polymer. Therefore, IBU-RL solid dispersions (coevaporates) were obtained and fully characterized in the solid state through spectroscopic, calorimetric, and x-ray diffractometric analyses. The in vitro release pattern of the drug, in the different chemical states, was studied for the coevaporates, compared with drug-RL physical mixtures, along with drug adsorption profiles from aqueous solutions on the surface of the polymer granules.

Matrix formation in sustained release tablets: possible mechanism of dose dumping

Conditions under which poly(ethyl acrylate, methyl methacrylate) 2:1 (poly(EA-MMA), Eudragit NE) forms a stable matrix were investigated in tablets with diclofenac sodium (DS) as an active substance. DS was granulated with the aqueous polymer dispersion. Granules and/or tablets were cured under various temperature and humidity conditions. A six position rotating disk (200 rpm) apparatus was used for the release studies conducted in 37 degrees C acid then phosphate buffer (0.4 M) pH 6.8 or buffer only as the dissolution media. Morphological characteristics of the tablet surface were observed under SEM. Changes in tablet structure upon curing were evaluated through changes in tablet mechanical characteristics. Modulus of rupture, Young's modulus, AUC, AUC(<max), AUC(>max), where AUC=AUC(<max)+AUC(>max), were determined by the three-point bending test. Some poorly cured tablets dose-dumped when placed directly into buffer but not if first placed in acid and then buffer. A higher content of polymer in the matrix, led to formation of a stronger polymer network upon higher curing temperature and/or longer curing duration, whereas relative humidity had a minor effect.

Characterization of ibuprofen as a nontraditional plasticizer of ethyl cellulose

This study describes the characterization of the plasticizing properties of ibuprofen (IBP) on hot-melt extruded ethyl cellulose (EC). The thermal behavior of hot-melt extrudates containing 0, 5, 10, and 20% (w/w) IBP was evaluated using modulated temperature differential scanning calorimetry. By means of comparison, co-evaporates containing the same concentrations of IBP and EC, were also evaluated. Both methods yielded solid solutions having one glass transition temperature indicating compatibility between drug and polymer. A similar decrease in glass transition temperature was noticed with increasing IBP concentration in the solid solutions prepared via both methods, indicating its plasticizing effect. The plasticizing efficiency was of the same magnitude as for the traditionally used plasticizers. Infrared spectroscopy was performed for better understanding of the chemical interactions in the molecular dispersions and confirmed the existence of hydrogen bonds between IBP and EC. Overall, the study has highlighted the plasticizing properties of IBP on EC during hot-melt extrusion.