How to measure and analyse the texture of food, cosmetics, pharmaceuticals and adhesives.

Monday, 28 October 2013

3 new testing solutions to take the drama out of pharma

Typical pharmaceutical capsuleIn one of the most tightly regulated industries across the globe, it goes without saying that quality control sits at the heart of all things pharmaceutical. 

Estimates of the cost of taking a drug to market sit comfortably at the $1 billion mark, with much of this vast spend being pumped into lengthy trials and rigorous analytical tests. Proving the efficacy, quality and safety of a pharmaceutical product to gain 100 per cent confidence and approval for market is, clearly, a significant investment.

Let’s take a look at some of the issues and review the latest innovations designed to help manufacturers overcome them...

Pharmaceutical testing innovation

For a long time, the industry has worked hard to develop and enhance quality control measures that will help to predict and refine product stability. Texture analysis instruments have played a big role. These offer repeatable, scientific quantification of material robustness, the results of which can identify product weaknesses and predict, and subsequently avoid, product failure.

Traditional tests have enabled the analysis of parameters such as tablet hardness, gel strength and mucoadhesion. While these tests continue to provide valuable data, materials analysis experts now have to respond to rapid innovation within the pharmaceutical industry, as new delivery and encapsulation formats are introduced. As a result, the scope and capabilities of testing instruments have widened significantly.

Capsule Tensile Rig in use on Texture Analyser Capturing capsule weakness

One of the latest developments in testing is the capsule tensile rig. This instrument measures the force required to split one half of a hard gel capsule. It allows manufacturers to investigate the effects of fillings on the mechanical strength of the capsule shell and identify changes that may impact their stability and long-term performance.

The simplified manufacture process of hard gelatine capsules and their ability to withstand higher filling temperatures is attractive to many manufacturers. Yet, the introduction of certain types of liquid, such as hydrophilic solvents, to hard capsules can often affect the mechanical properties of the shell, causing them to become brittle or soften. If the texture of a capsule is compromised, it may not be able to withstand handling and storage, resulting in fillings leaking from the capsule.

As effects are likely to be progressive, only displaying very small changes initially, compressive tests may not be able to distinguish the anomalies adequately. The capsule tensile rig is designed to help identify subtle degradation, providing valuable information which can be used to avoid subsequent capsule failure. For example, manufacturers can identify the effect of liquid filling on the strength and stability of capsules and therefore reformulate liquid type or capsule accordingly.

Before testing, the filling of the capsule is removed and the empty shell is mounted to a separating rod fixture on the TA.XTplus texture analyser. Vertical movement of the upper rod is then applied until the capsule is split apart, while Exponent software records the force required to do so. This test highlights three important parameters; elastic stiffness (if a linear region on the graph is present), tensile force and elongation at break point. A reduction in elastic stiffness and tensile strength occurs when capsules become softer, hence showing a tendency to fail.

Powder Compaction RigCracks under control

The pharmaceutical industry is one of the world’s biggest users of powder. Many products, such
as paracetamol, are produced in powder format and then compressed into tablets.

Powder compaction is an essential step in the manufacturing process and it is essential to avoid products cracking during processing. Their liability to failure is influenced by the powder’s processing properties, such as density variations introduced during die filling and/or compaction.

The characterisation of powder in its bulk format can enable manufacturers to predict the behaviour of the powder when compressed. However, the need for more targeted analysis of powder compaction has been identified and, as a result, the powder compaction rig was developed.

Available in high or low tolerance variants, this rig accurately measures the force and/or punch displacement required to compress powders into tablets. Using Exponent software, the powder compaction rig produces precise measurements that enable pharmaceutical product manufacturers to produce powder compacts with consistent porosity. It accurately assesses the force needed for the punch to travel a specified distance, or can be used in target force mode to assess the effect of fill level on tablet thickness.

The high tolerance powder compaction rig is suited to high force applications where the punch/die clearance is critical. This fixture is auto-aligned using a universal adapter, which saves time and avoids human error. The low tolerance version is suited to other powder compaction applications, such as assessing granule friability, where punch/die clearance is less important.

Bilayer Tablet Shear RigShear genius

Sophisticated methods for powder characterisation, along with analysis techniques for hardness and coating adhesion, have enabled manufacturers to obtain valuable data on the stability of standard tablet formats. However, the development of bi-layer tablet formats, which contain isolated immediate and controlled release component layers, has given rise to new analytical requirements.

Such formulations are increasingly popular as they provide efficacy for consumers as well as ease of production for manufacturers. Ensuring that one tablet layer does not impact on the other is instrumental to the remedial benefits of bi-layer medication, and to the safety of the consumer. But isolating two release components in separate layer formations can prove complex for manufacturers. The characteristics of each active pharmaceutical ingredient in a bi-layer tablet often differ, leading to problems in tablet composition which may in turn result in cross-contamination. Common issues include layer separation, insufficient hardness and inaccurate individual layer weight control.

Manufacturers need to be able to gauge the stability of the layers, to ensure the product reaches the user in its intended format. In response, the innovative bi-layer tablet shear rig has been launched. A unique new attachment, it analyses the strength of bi-layer tablets, allowing pharmaceutical manufacturers to identify weaknesses and improve the quality and stability of their products.

The rig is attached to the TA.XTplus texture analyser, which uses Exponent software to analyse layer separation. The tablet sample is placed in the central cavity of a guillotine-type blade, which is then compressed until the two components of the tablet are sheared apart. The force taken to shear the tablet, as well as the distance to failure, is calculated. The lower the force required to shear the tablet, the more likely it is that the layers will fail during manufacture, packing or consumption. Visual characterisation of the fracture surface enables quantification of the percentage of each fracture failure, which is important in enabling manufacturers to optimise adhesion between the two tablet components.

High stability for maximum profitability

The stability of a pharmaceutical product is paramount to the consumer’s acceptance of it, as well as to its subsequent efficacy and safety. It is vital, therefore, that manufacturers scientifically assess any potential changes in the structure or character of their products throughout processing and distribution. Texture analysis instrumentation has enabled manufacturers to do just this, offering targeted, repeatable testing that produces actionable data. As the pharmaceutical industry innovates, so materials analysis evolves, developing and adapting to provide new instruments for emerging test requirements.  

Watch our video about testing of materials  The Role of Texture Analysis in Pharmaceuticals

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