Influence of compression at elevated temperature on the compactibility of thermo-mechanically processed polymers

Effect of tableting temperature on tablet properties and dissolution behavior of heat sensitive formulations

The tableting process involves the conversion of mechanical to thermal energy. This study evaluated the influence of temperature on the tableting behavior of formulations with different compositions. The tableting machine was equipped with a thermally controlled die to mimic the heat evolution from tableting on an industrial scale. Six formulations containing binders with a comparably low glass transition temperature were examined. Besides the polymer type and concentration, the filler was varied. Paracetamol was chosen as the model active pharmaceutical ingredient. The investigation included alterations in tabletability, disintegration and dissolution. Elevated temperatures led to an enhanced tabletability. The polymer type and concentration were decisive for the extent of alterations. The variation of the filler composition played a minor role due to the high melting points of its components. The results were confirmed in disintegration and dissolution studies. A high binding capacity and a low glass transition temperature resulted in a stronger delay of disintegration. The dissolution was sustained. Increased concentrations of the binding polymer enhanced the effect. If the tableting behavior of a formulation is changed by elevated temperatures during formulation development and production, a change of the binder type or concentration should be considered to ensure a reproducible tablet quality.

Investigating the heat sensitivity of frequently used excipients with varying particle sizes

During tablet manufacturing an increase in the production temperature can lead to an alteration of tablet characteristics. In the present study, the influence of the initial particle size on the tableting behavior of ductile polymers upon temperature rise was investigated. Different grades of the respective materials were tableted at temperatures ranging from 22 to 70 °C. Alterations in tableting behavior were affected by the initial particle size. Smaller particle sizes led to a more pronounced decrease in yield pressure and net work of compaction during compressibility analysis. The results were confirmed in the tabletability studies. Tablets from binary mixtures with lactose containing smaller polymer particles yielded a stronger increase in tensile strength. Differences in the tensile strength increase of two grades from the same material correlated with the ratio of their median particle sizes. The alteration of compactibility profiles was also particle size dependent. The increase in solid fraction was more prominent for binary mixtures containing polymers with smaller particle sizes. However, the ratio of the median particle sizes of the compared grades showed no systematic effect. The results underline the importance of controlling the structural properties of a material carefully during formulation development and production. If a formulation responds to temperature variations, an increase in particle size might be beneficial to decrease its heat sensitivity.

Evaluation of In-Die Compression Data for a Deeper Understanding of Altered Excipient Properties upon Temperature Rise

The thermodynamic analysis of tablet formation includes the thermal and mechanical analysis during compression. The aim of this study was to evaluate alterations of force-displacement data upon temperature rise as an indicator for changed excipient properties. The tablet press was equipped with a thermally controlled die to imitate the heat evolution from tableting on an industrial scale. Six predominantly ductile polymers with a comparably low glass transition temperature were tableted at temperatures ranging from 22-70°C. Lactose served as a brittle reference with a high melting point. The energy analysis included the net and recovery work during compression, from which the plasticity factor was calculated. The respective results were compared to the changes in compressibility obtained via Heckel analysis. Elevated temperatures reduced the necessary work for plastic deformation for the ductile polymers, which was reflected in decreasing values for the net work of compaction and the plasticity factor. The recovery work slightly increased for the maximum tableting temperature. Lactose showed no response to temperature variations. Changes in the net work of compaction showed a linear correlation to the changes in yield pressure, which could be correlated to the glass transition temperature of a material. It is therefore possible to detect material alterations directly from the compression data, if the glass transition temperature of a material is sufficiently low.

Monitoring the weight and dimensional expansion of pyridostigmine bromide tablets under dynamic vapor sorption and impact of deliquescence on tablet strength and drug release

Changes of weight and axial expansion of tablets of the deliquescent drug pyridostigmine bromide with Kollidon SR were followed with relative humidity (RH) using dynamic vapor sorption and displacement transducer. The effects of RH on placebo and drug containing (API) tablets prepared at low and high compression were related to tablet strength and molecular changes. Tablet weight and expansion increased with RH, especially above RH 40%. Tablet rigidity and strength decreased linearly with moisture for placebo tablets whereas for API tablets there was decrease up to 50% followed by large drop at 60%. Raman spectra of tablets did not show chemical interactions due to moisture, but decreased intensity of drug peak at 2370 cm^-1 indicating solid state changes. Decrease of polymer peak intensities at 805 and 1740 cm^-1 occurred only in API tablets implicating drug deliquescence in polymer moisture sorption. X-ray diffraction and thermal analysis of tablets indicated complete drug liquefaction after exposure at 60% RH, which impacted great loss of strength but did not affect the sustained release profile. In conclusion, monitoring of the physical properties of tablets during production of deliquescent drugs is necessary to avoid pitfalls during downstream processes such as coating, packaging and storage.

Eudragit®: A Versatile Family of Polymers for Hot Melt Extrusion and 3D Printing Processes in Pharmaceutics

Eudragit® polymers are polymethacrylates highly used in pharmaceutics for the development of modified drug delivery systems. They are widely known due to their versatility with regards to chemical composition, solubility, and swelling properties. Moreover, Eudragit polymers are thermoplastic, and their use has been boosted in some production processes, such as hot melt extrusion (HME) and fused deposition modelling 3D printing, among other 3D printing techniques. Therefore, this review covers the studies using Eudragit polymers in the development of drug delivery systems produced by HME and 3D printing techniques over the last 10 years. Eudragit E has been the most used among them, mostly to formulate immediate release systems or as a taste-masker agent. On the other hand, Eudragit RS and Eudragit L100-55 have mainly been used to produce controlled and delayed release systems, respectively. The use of Eudragit polymers in these processes has frequently been devoted to producing solid dispersions and/or to prepare filaments to be 3D printed in different dosage forms. In this review, we highlight the countless possibilities offered by Eudragit polymers in HME and 3D printing, whether alone or in blends, discussing their prominence in the development of innovative modified drug release systems.

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.

Impact of Hot-Melt-Extrusion on Solid-State Properties of Pharmaceutical Polymers and Classification Using Hierarchical Cluster Analysis

The impact of hot-melt extrusion (HME) on the solid-state properties of four methacrylic (Eudragit® L100-55, Eudragit® EPO, Eudragit® RSPO, Eudragit® RLPO) and four polyvinyl (Kollidon® VA64, Kollicoat® IR, Kollidon® SR, and Soluplus®) polymers was studied. Overall, HME decreased Tg but increased electrostatic charge and surface free energy. Packing density decreased with electrostatic charge, whereas Carr’s and Hausner indices showed a peak curve dependency. Overall, HME reduced work of compaction (Wc), deformability (expressed as Heckel PY and Kawakita 1/b model parameters and as slope S′ of derivative force/displacement curve), and tablet strength (TS) but increased elastic recovery (ER). TS showed a better correlation with S′ than PY and 1/b. Principal component analysis (PCA) organized the data of neat and extruded polymers into three principal components explaining 72.45% of the variance. The first included Wc, S′ and TS with positive loadings expressing compaction, and ER with negative loading opposing compaction; the second included PY, 1/b, and surface free energy expressing interactivity with positive loadings opposing tap density or close packing. Hierarchical cluster analysis (HCA) assembled polymers of similar solid-state properties regardless of HME treatment into a major cluster with rescaled distance Cluster Combine Index (CCI) < 5 and several other weaker clusters. Polymers in the major cluster were: neat and extruded Eudragit® RSPO, Kollicoat® IR, Kollidon® SR, Soluplus®, and extruded Eudragit® L100-55. It is suggested that PCA may be used to distinguish variables having similar or dissimilar activity, whereas HCA can be used to cluster polymers based on solid-state properties and pick exchangeable ones (e.g., for sustain release or dissolution improvement) when the need arises.