PLASTIC VS. GLASS
BioPharm: What are the main drivers for using plastic instead of glass?
Reynolds (West): The drivers behind the use of plastic vials and syringes instead of glass are very different. In the case of glass vials,
the interest in plastic has been led by breakage concerns as well as various product recalls relating to glass particles.
Under certain conditions, glass particles (i.e., lamella) are formed by delamination on the surface of the glass vial. In
the past several years, FDA has initiated a number of recalls due to the risk that glass particulate may enter a patient through
drug products, particularly those that are administered intravenously. A study conducted by West indicated that clinicians
have concerns about the potential harmful effects of glass particles when injected into the body, especially directly into
the bloodstream. Plastic vials offer an alternative because the nature of the material eliminates delamination and reduces
the potential for breakage.
For prefillable syringes, the main drivers toward plastic have centered not only on glass breakage but also on the functionality
of the syringes, which must be siliconized when made of glass. It has been shown that when used in conjunction with certain
biologic products, particularly proteins, silicone oil can cause problems such as the formation of protein/silicone aggregates,
which may alter the integrity of the drug product. Another issue is that in the formation of a glass syringe, a tungsten pin
is used to create a hole. The needle is then bonded to the syringe using an adhesive. Residual tungsten has been shown to
cause stability problems with certain biologics. Use of plastic syringes provides an alternative that eliminates the needs
for silicone oil, tungsten, and adhesives.
In addition, prefillable syringe systems are often used in conjunction with a device, such as a self-injection system or needle-safety
system. The inherent variability in the dimensions of glass can lead to challenges when designing a device because many devices
put stress on glass products, particularly in the flange area, where breakage can occur.
There are many drugs that, by their very nature, simply do not work as intended when contained in glass. For those applications—whether
it is delamination or interaction with particularly aggressive materials—plastic may be the only option.
In addition, one of the many benefits of plastic is that it offers significant design flexibility and increased dimensional
precision. When developing more sophisticated devices such as pump systems and patch injectors, the use of a plastic container
may offer significant advantages by providing a consistent functionality for the system. For example, an electronic patch
injector platform technology (SmartDose, West) uses a polymeric (Crystal Zenith, Daikyo) cartridge that is designed to offer
a high degree of dimensional tolerance and functional consistency, which enables the device to function effectively. As another
example, a 1 mL-long plastic (Crystal Zenith, Daikyo) syringe has the potential to be filled with a volume in excess of 1
mL and maintain an effective seal.
Waller (SCHOTT): Plastic is used to produce various types of parenteral containers. We continue to experience an increase in discussion around
syringes. In other areas such as cartridges, vials, and ampoules, plastic use is a niche. The general advantages of plastic
are naturally drivers for using this type of container material. We do not, however, see a trend to switch from established
glass containers to plastic containers due to one specific advantage. We have the ability to evaluate the complete package
and consider all influencing variables. If glass delamination is a concern, specialized analytical services (SCHOTT Pharma
Services) can determine a suitable solution, possibly by using delamination-resistant, coated vials (Type I plus, SCHOTT).
Many pharma companies are looking at the syringe side when speaking about plastic containers. Polymeric, prefillable syringes
(TopPac, SCHOTT) are transparent like glass and offered with an integrated luer lock, which makes this system even more robust
than a glass syringe, in which the luer lock adapter is attached as a separate component. This solution is ideal for highly
viscous drugs, such as hyluronic acid. Flexible design and tight dimensional tolerances make these syringes compatible with
various intravenous connectors, thus ensuring patient safety.