Heat assisted twin screw dry granulation

The influence of input material properties on hot melt granules prepared using a counter-rotating batch mixer

OBJECTIVE

The objective of this study was to develop a method that enabled granulation in a counter-rotating batch mixer to emulate large scale dry twin screw granulation trials.

METHODS

Four granulations were prepared using counter rotating batch mixing for formulations containing a mixture of different particle sizes of the API (70% w/w) and polymer (30% w/w). Milled theophylline (MTHF; fine API) was blended with coarse hydroxypropyl cellulose (HPC MF; coarse polymer), theophylline (THF; coarse API) with fine hydroxypropyl cellulose (HPC EXF, fine polymer), and the other two formulations consisted of both components in the blend being fine or coarse.

RESULTS

The formulations selected for granulation had the lowest friction coefficient, f, as a function of drug load determined by the iShear^® powder flow rheometer. Despite the non-uniform chaotic and random nature of thermal granulation, each formulation granulated reproducibly, though the evolution for each was different.

CONCLUSION

This work highlighted that, firstly it is possible to measure plastic and frictional energy dissipation as product temperature. Secondly, granule growth and density were found to be proportional to the onset of polymer molecular mobility activated by the heat liberated from interparticle velocity differences via mechanical work (torque) required to move agglomerates through the mixer for the duration of each run.

Binder-free twin-screw melt granulation: An effective approach to manufacture high-dose API formulations

This study investigates the use of twin-screw binder-free melt granulation (BFMG) in the development of high-dose solid dose formulations for low melting point thermally stable drugs. Both ibuprofen and guaifenesin are examined. By granulating pure API powder, it is shown that BFMG can successfully be used to produce granules that contain 100% API. A design of experiments (DoE) response surface methodology was used to establish the design space for the end-product. The effects of the most relevant process variables (barrel operating temperature, powder feed rate, screw speed and screw configuration) on granule properties (outlet temperature, size distribution, morphology, flowability, compressibility, porosity) and tablet attributes (tensile strength and in-vitro dissolution) were thoroughly studied. Barrel temperature (alone or in interactions with the other variables) represented the most significant variable for both drugs since it governs the formation of granules by partial melting and subsequent agglomeration of the fed powder. Interestingly, the shear action originated by screw speed and screw configuration resulted in various significant responses depending on the drug substance, indicating that it can also be affected by the nature of the processed molecule. Flow properties were improved (i.e., lower Hausner ratio) for both drugs after formation of granules. Tabletability was also tested by preparing 600 mg tablets for all samples. Surprisingly, the resulting granules were highly compactible, requiring only 1% lubricant to form strong tablets containing 96% API and 3% disintegrant. The results also showed that tablets become harder as the granule size increased, especially for guaifenesin. As expected, in-vitro dissolution results indicated that tablets and capsules showed slightly slower dissolution rates than the granules.

Advances in Twin-Screw Granulation Processing

Twin-screw granulation (TSG) is a pharmaceutical process that has gained increased interest from the pharmaceutical industry for its potential for the development of oral dosage forms. The technology has evolved rapidly due to the flexibility of the equipment design, the selection of the process variables and the wide range of processed materials. Most importantly, TSG offers the benefits of both batch and continuous manufacturing for pharmaceutical products, accompanied by excellent process control, high product quality which can be achieved through the implementation of Quality by Design (QbD) approaches and the integration of Process Analytical Tools (PAT). Here, we present basic concepts of the various twin-screw granulation techniques and present in detail their advantages and disadvantages. In addition, we discuss the detail of the instrumentation used for TSG and how the critical processing paraments (CPP) affect the critical quality attributes (CQA) of the produced granules. Finally, we present recent advances in TSG continuous manufacturing including the paradigms of modelling of continuous granulation process, QbD approaches coupled with PAT monitoring for granule optimization and process understanding.

Recent progress in continuous manufacturing of oral solid dosage forms

Continuous drug product manufacturing is slowly being implemented in the pharmaceutical industry. Although the benefits related to the quality and cost of continuous manufacturing are widely recognized, several challenges hampered the widespread introduction of continuous manufacturing of drug products. Current review presents an overview of state-of-the art research, equipment, process analytical technology implementations and advanced control strategies. Additionally, guidelines and regulatory viewpoints on implementation of continuous manufacturing in the pharmaceutical industry are discussed.