A tale of two materials: What the glass vs. polymer debate really means

It’s a question we hear again and again. A question that has greater importance for pharmaceutical manufacturers as the popularity of prefilled syringes (PFSs) continues to rise, and manufacturers must not only develop an effective drug, but a streamlined and safe delivery system. A question that shows how pharmaceutical packaging plays a significant role in drug success, even as choosing the “right” packaging material for a drug remains a hot area of debate.

The question is seemingly simple: Is glass or polymer the better material for PFSs? Each has its strengths and weaknesses after all. But ultimately that’s the wrong debate to be having. Before analyzing the benefits and drawbacks of each material, pharmaceutical manufacturers need to start by assessing the user need for each PFS application.

The advantages and disadvantages of glass and polymer

Glass and polymer both play valuable roles in the PFS market, yet neither material is one size fits all. While glass is the preferred material for PFSs, polymer can also be a valid material for specific applications.

Glass is certainly the gold standard for parenteral packaging and also in the PFS space. Glass PFSs represent approximately 95 percent of all PFS applications and markets. Their barrier properties prevent oxygen and water vapor permeation from interacting with drug compounds. Plus, since glass is the most common material for PFSs, it’s already compatible with different filling machines and makes it easy for pharmaceutical companies to integrate glass PFSs into their operations. Regulatory authorities have vast experience with this material, which allows for a more streamlined pathway to drug approval. Finally, since glass is produced by multiple suppliers, supply chain disruptions shouldn’t halt drug production and supply.

However, glass does have some disadvantages. The material is more susceptible to breakage if not handled properly on the filling line or in the hands of users. Plus, glass syringe components, as well as the manufacturing process, can open the door for extractables and leachables, including sodium leaching or heavy metal release from the glass barrel; tungsten residues from the hot forming process; and contaminants from adhesives, silicone oil, the needle, and elastomer components. These extractables and leachables could interact with certain drugs and compromise drug stability. Glass PFSs might not be compatible with certain needleless Luer access devices (NLADs). In 2011, the FDA recommended that health care professionals avoid using needleless glass PFSs for adeonosine and amiodarone in emergency rooms, crash carts, and ambulances because of the potential for malfunctions with certain NLADs.

In recent years, polymer PFSs have grown in popularity, as they fulfill the requirements better than glass PFSs in certain applications. Polymer PFSs have a number of benefits. For example, polymer offers greater design flexibility while ensuring a low rate of breakage throughout the value chain. Plus, due to its material properties and manufacturing process, polymer is heavy metal and tungsten free, and also features low or no siliconization.

But like glass, polymer has its own disadvantages. Polymer has a much lower oxygen and gas barrier threshold than glass, increasing the potential for interaction with oxygen-sensitive drugs. It also exhibits an increased sensitivity to scratches if not handled correctly. Haze formation and discoloration could occur during sterilization processes.

Glass or polymer? Reviewing the case studies

Before deciding on a glass or polymer solution, drug manufacturers must assess the three Ps — product needs, process requirements, and practitioner and patient needs — prior to selecting a material for their packaging solution. By breaking down the application into these buckets, pharmaceutical manufacturers will be better able to determine the right material for their PFS. Still uncertain about what’s the right choice for your application? Here are three examples to help determine usage.

The first example is Heparin, an injectable anticoagulant. Heparin is often used as a self-administration drug, and for that reason, drug manufacturers must take in to account patient safety and easy integration with safety devices when developing PFS solutions. As a result, a glass solution continues to be the best option for Heparin packaging. Glass has been used to house Heparin for more than two decades without any major drug and packaging interactions, showcasing the stability of this solution. Additionally, the prominence of glass in this application allows manufacturers to work with multiple suppliers to fulfill their syringe demand and ensure easy regulatory pathways for drug approval. In this case, glass is the superior choice.

For dermal fillers (hyaluronic acid), on the other hand, the end user assessment is quite different. Dermal fillers are used in cosmetic applications to reduce wrinkles, and are often highly viscous substances. For that reason, these substances require packaging design flexibility that allows for a consistent gliding force to reduce the force of injection. In addition, polymer syringes have an integrated Luer lock to prevent leakage and needle pop-off. As a result, polymer tends to be the material of choice for dermal filler packaging. Polymer syringes are more break resistant than glass, and can be engineered for specific sizes, inner diameters, and finger flange designs while maintaining tight tolerances during manufacturing.

Finally, let’s examine biotech drugs. Stability is critical for biopharmaceuticals, and for that reason, the drug’s packaging must be selected with care to prevent unwanted interactions. While both polymer and glass offer long-term drug stability for biopharmaceuticals, the final material choice for these sensitive drugs comes down to the end use. Glass not only offers enhanced functionality for end users, but also promises streamlined filling on the manufacturing line. Plus, since glass has been a longstanding material in the packaging of injectable pharmaceuticals, especially biotech drugs, it’s well known and accepted by various regulatory authorities. Yet, polymer PFSs could offer advantages for biotech packaging, including design flexibility, tighter tolerances, and break resistance for a better fit with autoinjectors. For biotech applications, it is tricky to decide on one particular material, and therefore pharmaceutical manufacturers must assess the end use before choosing the right PFS.

The importance of partner collaboration

There are many suppliers for both glass and polymer PFS solutions, but choosing the right partner is vital for a drug’s success. While glass is the dominant material used for PFS applications, polymer might also be a viable choice for certain drug applications.

Drug manufacturers must consider drug-container interactions, machinability, material quality and availability, and regulatory compliance when selecting the right material for their application. But most importantly, drug developers must weigh the needs of users in terms of functionality, safety, and comfort. Ultimately, understanding the demands of the customer is crucial in offering the right solution.

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Hello, I’m Anil Busimi, Head of Global Product Management in SCHOTT’s syringe division. I joined SCHOTT in 2003, and have since held a number of different positions, including Business Development Manager for microarrays, Consultant in corporate strategy and development, and Strategic Business Manager for the global pharmaceutical packaging division. I was the Global Product Manager for SCHOTT’s TopPac syringes before taking on my current role. I hold a master’s degree in agriculture and genetics, as well as an MBA.

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