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Question: Barrel Filling vs Tip Filling a Syringe – Which approach should be used?
Answered by Josh Russell, VP of Sales & Marketing
Well, one of the things we love talking about at AST is ready-to-use containers. There are a lot of rewarding aspects of the work we get to do, and one of those highlights is when a customer says, “Alright, AST, we have this amazing product we need to fill in a specific type of container; what’s the best way you can make that happen?” And in the elaborate world of RTU containers, that’s a question that excites and motivates our team every time.
A container type we often work with and love to design for is the pre-filled syringe.
Pre-filled syringes have seen remarkable growth in use and development in recent years. This is due to significant advantages in process enhancements and sterility assurance offered by RTU packaging as a whole, and the versatility, safety, and accessibility specific to pre-filled syringes, particularly in healthcare settings. These solutions provide manufacturers and patients alike with a higher standard of quality.
As our project management and engineering teams work with our customers to configure a fill line to a product’s specifications, one question that may arise is: are there different ways to fill a syringe? In the pharmaceutical industry, there’s the conventional, widely used method of filling directly over the top of the syringe, or what’s known as barrel-filling, and then there’s tip filling, a lesser utilized method that fills a syringe through the luer connection at the tip of the container. For many of our friends in the compounding pharmacy world, tip filling is a commonly used method.
Tip Filling
Tip filling has been historically useful in a compounding/lower regulative-standard production setting. In this configuration, syringes are filled employing a simple, bottom-up method either manually or semi-automatically. Tip filling requires pre-plunged, pre-sterilized syringes and can be configured to fill via pump, product draw, or a combination approach, and can be designed with or without single-use pathways often done within a biosafety cabinet. Some benefits of tip filling include simplicity of operation and the ability to minimize air bubbles. Uses for tip filling include highly viscous products, infusion settings, and needle-free applications.
For many in the pharmaceutical industry, however, tip filling has substantial drawbacks. Tip fill operations, while clean, are generally manual and can introduce substantial contamination risk. Additionally, manual draws can lead to accuracy issues. When considering the regulatory framework and the increased emphasis on aseptic environments and contamination control, especially within the compounding pharmacy industry in recent years, fill-close solutions that don’t offer a high level of sterility assurance and product quality measures simply aren’t as tenable as they were decades ago. Additionally, essential QC tools like automated in-process weight check systems aren’t available on tip fill options, and tip filling as a whole has significant process restrictions due to throughput and luer-based format limitations.
Barrel Filling:
The most common way to fill syringes is by utilizing pumps and single-use fluid paths to dispense product directly into the syringe barrel. This process should be carried out using proper aseptic technique whether automated or done manually. Pump technology like peristaltic or rotary piston can be used to dispense fluid accurately. The choice of pump depends on the properties of the product being filled (a peristaltic pump is ideal for low-shear dispensing, and a rotary piston pump is ideal for high-viscosity liquids). The right technology allows products to be filled accurately with minimal waste. Some further benefits of barrel filling include:
- More container flexibility, including syringes with staked needles
- Higher throughput
- Higher accuracy, less product waste
- Numerous semi-automated and fully automated processing options available
- Ability to fill in nested configurations.
This approach can be combined with vacuum, vent-tube, or combination stoppering depending on the need of the product and is adaptable to the full range of presterilized RTU syringes.
While there might be select occasions where tip filling may be preferred, the advancements in the conventional aseptic filling of syringes have made it the overwhelming choice in our industry. And with improvements in pump technology and stoppering methods, barrel filling can be executed to a high degree of precision, with minimal air introduced and minimal headspace, for consistent high-quality production, improved compliance, and overall reduction of risk.
Reach out to one of our team members today for an in-depth walk-through of AST’s aseptic filling solutions.
