Pre-plasticization of thermal binder facilitates processing and granule growth during melt granulation of gabapentin using co-rotating twin screw extruder

Optimizing twin-screw melt granulation: The role of overflight clearance on granulation behavior

Twin-screw melt granulation (TSMG) relies on the dispersive and distributive mixing at the kneading zone for granule growth to happen highlighting the critical role played by the kneading elements in TSMG. Despite extensive research conducted on the impact of screw geometry in melt compounding, there is not enough literature for TSMG. Disc width for the kneading elements was 2 mm, contrary to the standard 5 mm. The objective of this study was to evaluate if varying overflight clearance (OC) can alter the paradigm for TSMG. The new elements reduce the peak shear at kneading zone however a higher barrel temperature and degree of fill (DoF) is required to compensate to attain similar granule attributes. The change in DoF was achieved through a combination of modified screw configuration to pre-densify powders before kneading and processing at a lower screw speed. Despite the higher barrel temperature, process optimization of thermally unstable gabapentin was carried out. Using the new elements, compressible granules (Tensile strength > 2 MPa) with low % GABA-L content were manufactured despite increasing OC to 0.4 mm. Granule stability at 40 °C, ambient humidity for 6 months indicated gabapentin was stable (% GABA-L ≪0.4 %) despite a high barrel temperature of 120 °C.

Computer numerical control (CNC) carving as an on-demand point-of-care manufacturing of solid dosage form: A digital alternative method for 3D printing

Computer numerical control (CNC) carving is a widely used method of industrial subtractive manufacturing of wood, plastics, and metal products. However, there have been no previous reports of applying this approach to manufacture medicines. In this work, the novel method of tablet production using CNC carving is introduced for the first time. This report provides a proof-of-concept for applying subtractive manufacturing as an alternative to formative (powder compression) and additive (3D printing) manufacturing for the on-demand production of solid dosage forms. This exemplar manufacturing approach was employed to produce patient-specific hydrocortisone (HC) tablets for the treatment of children with congenital adrenal hyperplasia. A specially made drug-polymer cast based on polyethene glycol (PEG 6,000) and hydroxypropyl cellulose was produced using thermal casting. The cast was used as a workpiece and digitally carved using a small-scale 3-dimensional (3D) CNC carving. To establish the ability of this new approach to provide an accurate dose of HC, four different sizes of CNC carved tablet were manufactured to achieve HC doses of 2.5, 5, 7.5 and 10 mg with a relative standard deviation of the tablet weight in the range of 3.69-4.79%. In addition, batches of 2.5 and 5 mg HC tablets met the British Pharmacopeia standards for weight uniformity. Thermal analysis and X-ray powder diffraction indicated that the model drug was in amorphous form. In addition, HPLC analysis indicated a level of purity of 96.5 ± 1.1% of HC. In addition, the process yielded mechanically strong cylindrical tablets with tensile strength ranging from 0.49 to 1.6 MPa and friability values of <1%, whilst maintaining an aesthetic look. In vitro, HC release from the CNC-carved tablets was slower with larger tablet sizes and higher binder contents. This is the first report on applying CNC carving in the pharmaceutical context of producing solid dosage forms. The work showed the potential of this technology as an alternative method for the on-demand manufacturing of patient-specific dosage forms.

Twin-Screw Melt Granulation for Oral Solid Pharmaceutical Products

This article highlights the advantages of pharmaceutical continuous melt granulation by twin-screw extrusion. The different melt granulation process options and excipients are described and compared, and a case is made for expanded use of twin-screw melt granulation since it is a flexible and continuous process. Methods for binder selection are profiled with a focus on rheology and physical stability impacts. For twin-screw melt granulation, the mechanism of granulation and process impact on granule properties are described. Pharmaceutical applications of melt granulation ranging from immediate release of soluble and insoluble APIs, taste-masking, and sustained release formulation are reviewed, demonstrating the range of possibilities afforded by twin-screw melt granulation.