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The Preferred Container Material for Parenteral Pharmaceutics
Since time immemorial, glass has been the preferred container material for parenteral pharmaceutics. A new generation of biotech drugs however is placing high demands on their container systems. With advanced technologies, glass can be adapted to these demands. On the other hand, comparatively young materials such as cyclic olefins create new options for the packaging of parenterals.

In common practice, type I glass is the established packaging material for parenterals. It is transparent which enables visual inspection, it is inert against most substances, it is stable for nearly indefinite periods and it is impermeable to gases and water vapour. Last but not least it is comparatively inexpensive. Nevertheless, there are drawbacks that become even more significant in connection with some highly sensitive and highly expensive modern drugs. In the context of new biotechnological drugs, the surface properties of glass containers are of paramount importance. Borosilicate glass interacts with waterbased solutions in different ways depending on the pH. Closely related to this problem is the phenomenon of glass delamination. Glass flakes may peel off the surface after sufficient amounts of surrounding glass are degraded. This process is influenced by many parameters on the glass forming and fill and finish processing side.
Some problems of surface degradation can be solved by coating the surface with silicone oils. Unfortunately, the silicone treatment has its own problematic side effect with some biotech drugs. Some proteins tend to coagulate around microscopic silicone droplets. The resulting protein aggregates may lead to an increased immunogenicity of the drug product.

The most successful attempts to enhance the performance of glass containers are based on thin film technologies. For more than ten years, pure silica (SiO2) coatings have been applied to the inner surfaces of glass containers. The silica layer acts as a diffusion barrier, preventing interaction of the glass matrix with the drug.
Glass as Syringe Material
Prefillable syringes have become an important packaging option for protein-based drug products. In the production of syringes, some specific challenges have to be overcome. First of all, the use of silicone is essential to ensure system functionality by providing the required break loose and gliding forces of the plunger. Another specific source for potential contamination are traces of tungsten oxide left behind in the forming process of the luer channel. Last but not least, the cannulae have to be glued in with UV-cured urethane methacrylate that may act as another source of contamination.
Plastic an Alternative to Glass
In the past, the high cost and complexity of meeting regulatory requirements discouraged producers of parenteral drugs to consider any materials other than the well-established glass. As new, demanding types of proteins and peptides enter the market, innovative materials for parenteral packaging are being scrutinised more closely. The polymers of choice for the packaging of parenterals are cyclic olefin polymers/ copolymers (COP/COC), also known as polycyclicolefin (PCO).
Some properties of Cyclic olefins are comparable to glass. Both materials are transparent and durable. Although they only have limited resistance to organic solvents, they are superior to glass in other categories. The breakage resistance of the polymer is higher, the pH-range tolerance is wider and there is no leaching of metal ions. Another feature which is particularly important for the storage of expensive drug products is the excellent drainability of COP containers.
On the other hand, cyclic olefins also have disadvantages. They are more susceptible to scratches than glass and their material standardisation is (not) compendial. One major disadvantage is their degree of gas and water vapor permeability.

As in glass applications, the performance of cyclic olefin containers can be considerably enhanced by multilayer technologies. For example COP layers on a polyamide (PA) core combine the excellent surface properties of COP with a highly reduced oxygen permeability and a better break resistance.
Another technology to lower the permeability of cyclic olefin containers is the deposition of a barrier layer on a COC surface. Compared to polypropylene (PP), gas permeability can be decreased by a factor of 5 to 20.
Prefillable Cyclic Olefin Syringes
In the booming market sector of prefillable syringes, cyclic olefin has become a serious option (Schott TopPac®; BD Sterifill SCF™; West/Daikyo Crystal Zenith®, Gerresheimer/ Taisei Kako Clearject™). Ready-to-use plastic prefillable syringes satisfy the same regulatory requirements as glass readyto- use syringes. The main reason for the use of cyclic olefins is again their superior performance, especially with biotech, cytotoxic and high-viscous drugs. Polymer syringes do not have the disadvantages of glass barrels such as breakage, metal ion leaching and silicone oil droplets.

A Coexistence of Materials
Borosilicate type 1 glass and cyclic olefin polymers/copolymers both qualify as excellent materials for the primary packaging of parenterals. Nevertheless, none of these materials are flawless.
Glass will always be the preferred material for small molecule drugs, drugs with medium pH or low sensitivity to pH-shift and for drugs that are sensitive to oxidation or humidity. On the other hand, it can be advantageous to package large molecule biotechnological drugs and extremely expensive drugs in cyclic olefin containers, especially in prefillable ready-to-use plastic syringes. Neither material will replace the other, and glass and cyclic olefins will continue to coexist. Pharma packaging suppliers are constantly working on new or optimised surface coatings and even multi-layer technologies to improve the quality of glass and plastic to containers to address the increasingly demanding requirements of the pharmaceutical industry.