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What do the Olympics and parenteral primary containers have in common?

In the run up to the Tokyo 2020 Olympics, the International Olympic Committee added an additional word to the Olympic motto – “becoming Faster, Higher Stronger – Together”. This phrase ties together many of the challenges, and solutions, to choosing and using a primary container in parenteral drug delivery. Over recent years the trend towards higher volumes and viscosities has driven the need for faster flow rates, to allow higher volumes to be delivered in an acceptable time. This has led to a need for higher forces and therefore stronger devices and primary containers. In order to tackle the new challenges this brings, it is key for formulation, device and primary container development groups or companies to work closely together.

With this in mind, how do you choose a successful primary container for a parenteral device?

Understand what you are working with

As with any sport, understanding the rules and the terrain are important, and it is similarly important to understand the drug formulation and how it might change during development. Viscosity can be impacted by many things, including temperature, aging and batch variability, which can have a big influence on what container is needed. Material compatibilities are also key as these can immediately disqualify some configurations.

Keep it simple, keep it standard

Tried and tested technologies rarely make Olympic headlines, and while innovations may have led to the famous marginal gains of the GB cycling team, sticking to standard primary containers can significantly de-risk the development of a product. Using standard materials and geometries open up a wider range of devices and can simplify the transfer from lab to manufacture. However, if you are aiming for a platform that may need multiple primary containers, be sure to understand how different “standard” options compare. ISO 11040 covers a wide range of products which are not always interchangeable.

Minimise resistance

Whether it’s special materials in swimming suits or aero frames in track cycling, it’s important to make the most of what power you have. With a primary container, one of the key challenges is ensuring the formulation can flow out of the needle. Using different gauges and wall thicknesses can maximise the needle bore and minimise the resistance to flow. Newer options such as tapered or shorter needles can also provide a reduction in resistance, which can make delivery easier. However, with all of these it’s important to understand their compatibility with the other aspects of the primary container, as well as their availability for development and testing. Alongside ensuring the drug can flow out, minimising other losses in the system can also be key to achieving acceptable outputs. For example, glide force can be a significant energy sink in the system and can vary significantly across different primary container combinations.

Is strength enough?

As any weightlifter or gymnast can attest to, support is key. Having appropriate support is important to ensure load paths are appropriately directed and for the primary container to be given every opportunity to perform to its full potential. Using our knowledge of the drug, we can check the potential needles and power sources involved in the primary containers, to ensure they are strong enough based on our assumptions about material properties.

However, it should be kept in mind that there are many factors which can affect the apparent strength of the container. These may include the support of the syringe (flange support can generate huge stresses), and the impact of the power source (does it provide a gentle consistent load or are shock loads an issue?). Processing of the primary container, whether handling or sterilisation processes, can also change material properties.

All of these rules are likely to require many iterations to balance the competing needs and get to a successful product. Much like an Olympic team, to achieve this close collaboration between all the parties involved is key.

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