Powder Flow: Powder characterization for formulators

Powder characterization for formulators

Accelerating product development through formulation into successful manufacture and on to the market place, is an important goal for the pharmaceutical industry. Optimising the formulation process and more efficient production are strong themes as revenues come under intense pressure. For formulators the principal focus is developing a product that delivers desirable clinical performance, but manufacturing demands are increasingly influential. Steps taken at an early stage to thoroughly scope the links between process and product variables, as advocated by QbD, can pay dividends over the long term. This is especially true for powders, where fundamental compatibility between the formulation and plant builds quality into manufacture from the outset.

Cost-effective tools for sensitive powder characterization are an essential part of the formulator's armoury. Universal powder testers (such as the FT4 Powder Rheometer? from Freeman Technology) are especially useful, their value deriving from a unique combination of features which crucially includes:
Multi-faceted powder characterization (shear, bulk and dynamic properties)
Exemplary reproducibility
Process relevant measurements
 

 Fgure 1 - FT4 Powder Rheometer? from Freeman Technology

Describing a powder using an array of variables rather than a single number is now widely accepted as the optimal approach since the complexity of powder behaviour cannot be adequately captured using just one descriptor. Instruments that offer multiple measurement strategies are an efficient way of gaining maximum insight, making it easier for formulators to accurately identify the specific powder properties that correlate with aspects of clinical performance. For example, research has shown that the aerosolisation characteristics of dry powder inhaler formulations correlate directly with aerated flow energy. This is a dynamic parameter not discernable with either shear or bulk property methods, so this correlation would be missed using conventional, single parameter tests.
 
Excellent reproducibility enhances the sensitivity of any analytical instrument sharpening decision-making processes throughout the product lifecycle. The cross-correlation of different variables is severely hampered by 'noisy' data that can make it impossible to tell whether differences between samples are real or simply measurement inaccuracies. For the formulator, sensitive analysis therefore provides fine detail, enhancing understanding of the factors influencing product performance.

Finally, process relevant data means that researchers can predict the in-plant behaviour of a powder with just small amounts of sample, offering the opportunity to formulate on the basis of process, as well as clinical performance.

Producing a database of reproducible powder properties helps to break down the traditional barriers between formulation, process design and operation, promoting a more holistic multidisciplinary approach to development that successfully captures the knowledge of different disciplines. Lessons learned during pilot and full-scale operation can inform new development if the information is presented in a usable form.

For example, operational staff may know that blend A performs well in a vacuum vial filling process while blend B is more problematic. Analyzing the powders reveals that the poor performance of B can be quantified in terms of permeability and the change in basic flow energy induced by applying a vacuum. This is valuable information for formulators developing a new product that will be processed in a similar way.

Comprehensive, sensitive, process-relevant powder characterization is clearly vital for effective formulation. Universal powder testers meet this need and are consequently a cost-effective solution for formulators seeking to streamline and improve development.

Author Biography - Tim Freeman, Managing Director, Freeman Technology

Tim Freeman is Managing Director of powder characterisation company Freeman Technology for whom he has worked since the late 1990s. He was instrumental in the design and continuing development of the FT4 Powder Rheometer? and the Uniaxial Powder Tester. Through his work with various professional bodies, and involvement in industry initiatives, Tim is an established contributor to wider developments in powder processing.

Tim has a degree in Mechatronics from the University of Sussex in the UK. He is a mentor on a number of project groups for the Engineering Research Center for Structured Organic Particulate Systems in the US and a frequent contributor to industry conferences in the area of powder characterisation and processing. A past Chair of the American Association of Pharmaceutical Scientists (AAPS) Process Analytical Technology Focus Group Tim is a member of the Editorial Advisory Board of Pharmaceutical Technology and features on the Industry Expert Panel in European Pharmaceutical Review magazine.  Tim is also a committee member of the Particle Technology Special Interest Group at the Institute of Chemical Engineers, Vice-Chair of the D18.24 sub-committee on the Characterisation and Handling of Powders and Bulk Solids at ASTM and a member of the United States Pharmacopeial (USP) General Chapters Physical Analysis Expert Committee (GC-PA EC).

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