Tuning the Polymer Release from Hydrophilic Matrix Tablets by Mixing Short and Long Matrix Polymers

The effect of polymeric binder type and concentration on flow and dissolution properties of SMEDDS loaded mesoporous silica-based granules

Self-microemulsifying drug delivery systems (SMEDDS) are lipid-based formulations, designed to improve the solubility of poorly-water soluble drugs. Mesoporous silica is frequently used for SMEDDS solidification by various techniques. One of them is wet granulation, which enables achieving both high SMEDDS load and good flow properties. This study investigated the effect of six polymeric binders' addition to granulation dispersion (GD) (povidone K30, povidone K90, copovidone, Pharmacoat® 603, Pharmacoat® 615 and Methocel™ K100 Premium LV) on characteristics of produced SMEDDS granules, prepared by wet granulation. By incorporation of polymer in GD, it was possible to produce mesoporous silica-based free-flowing granules, with preserved self-microemulsifying properties, responsible for improved in vitro release of carvedilol. The incorporation of higher molecular weight binders resulted in slower in vitro release, while high binder concentration was related to faster drug release. The highest release rate was achieved with povidone K30 at 7.45 % binder concentration, as corresponding granules exhibited complete drug release already in 5 min. Granulation method (manual vs. high-shear) influenced the release rate of carvedilol as it was released slower from SMEDDS granules prepared using the granulator. Finally, SMEDDS tablet formulation was optimized to achieve maximum granule content and adequate tablet hardness. Increased granule content found to negatively influence tablet hardness, as maximum granule content of 25 % was needed to obtain appropriate hardness. Such tablets exhibited short disintegration time, so this final prototype can be considered as orodispersible tablet.

Stability of Abuse-deterrent properties of PEO-based Abuse-deterrent formulation

Abuse of opioid drug products is a national health crisis in the US. To deter abuse, a number of drug products with abuse-deterrent (AD) properties have been approved by the US Food and Drug Administration (FDA). For abuse deterrence, it is critical to maintain the AD properties during the product shelf life. However, no information on the stability of AD properties during product shelf life is publicly available. In this study, stability of AD properties of surrogate AD formulation (ADF) of opioid active pharmaceutical ingredients (APIs) were studied. Surrogate extended release (ER) AD tablets were prepared by direct compression using Diltiazem HCl (model drug), polyethylene oxide (PEO WSR 301) polymer and magnesium stearate followed by curing at 70 °C for 30 mins. The stability studies were conducted at 25 °C/60 % RH and 40 °C/75 % RH storage conditions for 12 months (M) and 6 months (M), respectively. In vitro characterization and evaluation of AD properties of tablets were performed. As anticipated, the curing process increased the crushing strength of the tablets. However, the tablets could still be manipulated and compromised leading to an enhancement in the amount of drug extracted in solvents (e.g., water, alcohol), regardless of extraction temperature as well as tablet storage condition and time. Furthermore, the granule particle size as well as viscosity in water of manipulated samples were found to be lower for tablets stored at 25 °C/60 % RH or 40 °C/75 % RH for 12 M or 3 M/6M, respectively. The changes in AD properties eased the syringeability of hydrated samples and ultimately led to the withdrawal of higher amounts of drug into the syringe, thereby, impacting the abuse deterrence potential of the formulation by an IV route. These data demonstrated that the stability of AD properties (i.e., granule particle size, viscosity and syringeability-injectability) of PEO-based tablets was dependent on the storage condition. In conclusion, the design of AD formulation and setting of product quality profile should take into consideration the stability of AD properties during the product shelf life.

Continuous Monitoring of the Hydration Behavior of Hydrophilic Matrix Tablets Using Time-Domain NMR

Time-domain NMR (TD-NMR) was used for continuous monitoring of the hydration behavior of hydrophilic matrix tablets. The model matrix tablets comprised high molecular weight polyethylene oxide (PEO), hydroxypropyl methylcellulose (HPMC), and polyethylene glycol (PEG). The model tablets were immersed in water. Their T₂ relaxation curves were acquired by TD-NMR with solid-echo sequence. A curve-fitting analysis was conducted on the acquired T₂ relaxation curves to identify the NMR signals corresponding to the nongelated core remaining in the samples. The amount of nongelated core was estimated from the NMR signal intensity. The estimated values were consistent with the experiment measurement values. Next, the model tablets immersed in water were monitored continuously using TD-NMR. The difference in hydration behaviors of the HPMC and PEO matrix tablets was then characterized fully. The nongelated core of the HPMC matrix tablets disappeared more slowly than that of the PEO matrix tablets. The behavior of HPMC was significantly affected by the PEG content in the tablets. It is suggested that the TD-NMR method has potential to be utilized to evaluate the gel layer properties, upon replacement of the immersion medium: purified (nondeuterated) water is replaced with heavy (deuterated) water. Finally, drug-containing matrix tablets were tested. Diltiazem hydrochloride (a highly water-soluble drug) was employed for this experiment. Reasonable in vitro drug dissolution profiles, which were in accordance with the results from TD-NMR experiments, were observed. We concluded that TD-NMR is a powerful tool to evaluate the hydration properties of hydrophilic matrix tablets.

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

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

Assessment of critical material attributes of polyethylene oxide for formulation of prolonged-release tablets

Physicochemical evaluation of polyethylene oxide (PEO) polymers with various molecular weights was performed at molecular (polymeric dispersion) and bulk level (powders, polymeric films, and tablets) with the aim of specifying polymer critical material attributes with the main contribution to drug release from prolonged-release tablets (PRTs). For this purpose, grades of PEO with low, medium, and high viscosity were used for formulating PRTs with a good soluble drug substance (dose solubility volume 15 ml). The results revealed a good correlation (r²=0.88) between in vivo data (pharmacokinetic parameters: C_max and AUC) and the elastic property of PEO films determined with the nanoindentation method, demonstrating that film level can also be used for the in vivo prediction of drug dissolution. The study confirmed that polymer molecular weight and its viscosity are the most important critical material attributes affecting drug dissolution (in vitro) and in vivo bioavailability (e.g. C_max and AUC). Our research revealed that the nanoindentation technique can distinguish well between various types of polymers, classifying PEO as the most ductile and polyvinyl alcohol as the most brittle. Finally, our study provides an approach for the determination of exact physical attributes of PEO as a critical material attribute from clinically relevant data, and it therefore fulfills the basic principles of product development by Quality by Design.

Evaluating the swelling, erosion, and compaction properties of cellulose ethers

Swelling, erosion, deformation, and consolidation properties can affect the performance of cellulose ethers, the most commonly used matrix former in hydrophilic sustained tablet formulations. The present study was designed to comparatively evaluate the swelling, erosion, compression, compaction, and relaxation properties of the cellulose ethers in a comprehensive study using standardised conditions. The interrelationship between various compressional models and the inherent deformation and consolidation properties of the polymers on the derived swelling and erosion parameters are consolidated. The impact of swelling (K_w) on erosion rates (K_E) and the inter-relationship between Heckel and Kawakita plasticity constants was also investigated. It is evident from the findings that the increases in both substitution and polymer chain length led to higher K_w, but a lower K_E; this was also true for all particle size fractions regardless of polymer grade. Smaller particle size and high substitution levels tend to increase the relative density of the matrix but reduce porosity, yield pressure (P_y), Kawakita plasticity parameter (b^-1) and elastic relaxation. Both K_W versus K_E (R² = 0.949-0.980) and P_y versus. b^-1 correlations (R² = 0.820-0.934) were reasonably linear with regards to increasing hydroxypropyl substitution and molecular size. Hence, it can be concluded that the combined knowledge of swelling and erosion kinetics in tandem with the in- and out-of-die compression findings can be used to select a specific polymer grade and further to develop and optimize formulations for oral controlled drug delivery applications.

The influence of vitamin E succinate on the stability of polyethylene oxide PEO controlled release matrix tablets

Hydrophilic matrices are a principal technology used for extended release (ER) oral dosage forms and a recent review concluded that their development is currently one of the most important challenges in pharmaceutical research. High molecular weight polyethylene oxides (PEOs) have been proposed as an alternative to hydroxypropylmethylcellulose (HPMC) for the manufacture of controlled release matrix tablets. It is known that PEO's are prone to oxidative degradation which can occur by chain scission and can be catalyzed by metal ions. In this study, we investigated the stability of PEO matrix tablets, of different molecular weight, containing diltiazem hydrochloride, when stored at 40 °C. The results show that there were dramatic increases in the release rate of the diltiazem following storage over only a few weeks, resulting in immediate release profiles after eight weeks, even for the highest molecular weight grade. We employed Gel permeation chromatography (GPC), viscosity and differential scanning calorimetry (DSC) techniques to try and determine the underlying causes of these dramatic shifts in dissolution profiles on storage. The results showed that there were significant decreases in the molecular weight of the PEO's during storage. The second part of the study looked at the addition of three different levels of vitamin E succinate to the tablets. The results clearly demonstrate the ability of the added antioxidant to reverse the significant reductions in molecular weight seen using GPC, viscosity and DSC. Importantly the addition of the antioxidant was able to stabilize the release profile of the diltiazem especially when present at a 1% level. Researchers and those working in pharmaceutical development should be aware of the potential stability risks when making matrix tablets containing PEO's and may wish to consider the addition of an antioxidant to the tablet formulation.

Influence of different polymer types on the overall release mechanism in hydrophilic matrix tablets

The effect of three different types of polymer chain structures on the polymer release from hydrophilic matrix tablets was investigated by comparing a synthetic semi-crystalline linear polymer (PEO), a branched amorphous polysaccharide (dextran) and an amorphous substituted cellulose derivative (HPMC). The polymer release rates for tablets containing mixtures of high and low molecular weight grades in different ratios were determined by using a modified USP II method and a SEC-RI chromatography system. The results showed that independent of polymer type: (i) plots of the release versus time had similar shapes, (ii) the release of long and short polymer chains was equal and no fractionation occurred during the release and (iii) the release rate could be related to the average intrinsic viscosity of the polymer mixtures. This confirms the hypothesis that the release rate can be related to a constant viscosity on the surface of the hydrophilic matrix tablet and that it is valid for all the investigated polymers.

Molecular information on the dissolution of polydisperse polymers: Mixtures of long and short poly(ethylene oxide)

A systematic study of the dissolution of dry, polydisperse poly(ethylene oxide) (PEO) samples, obtained from mixtures of low-molecular-weight and high-molecular-weight PEO, was made. During the dissolution process, the individual release of the low- and high-molecular-weight fractions was monitored. The high-molecular-weight/low-molecular-weight ratio controls the release rate, and the fraction of high-molecular-weight polymers dominates the effect on the overall release rate in mixed PEO tablets. Both fractions are released at the same rate during the main part of the dissolution process; however, during the initial dissolution period a fractionation occurs. The release rate is not a unique function of the average molecular weight of the polymer, but also depends on the polydispersity. By contrast, the average dimension of a polymer coil, as given by the intrinsic viscosity, gives a good prediction of the release rate irrespective of the polydispersity or details of the molecular weight distribution.

A model for the drug release from a polymer matrix tablet—effects of swelling and dissolution

A model for simulating the drug release from a swelling and dissolving polymer tablet is presented and verified to data. The model is based on a mechanistic approach, and it can therefore be employed to study the sensitivity of true physical constants, for instance the drug diffusion coefficient or the drug solubility. The model generates the drug and polymer release profiles and the front positions of the total tablet, the solid core, and of the solid-drug-solubilized-drug interface. The convective contribution to mass transfer is shown to be of great importance. This is most markedly noticed for slowly diffusing drugs. In a simulation with a low value of the drug diffusion coefficient, it is shown that the initial drug release rate is faster than the polymer dissolution rate, followed by a second stage with a slower drug release rate. Furthermore, it is shown that polymer dissolution influences the drug release profile significantly, but not the front position of saturated drug in the gel layer. The model is verified against drug release and polymer dissolution data for the slightly soluble drug Methyl paraben and the soluble drug Saligenin in a poly (ethylene oxide) tablet, resulting in good agreement between model and experiments.