Prefilled syringes have become important options in the packaging, distribution, and delivery of pharmaceutical solution products,
particularly biopharmaceuticals. This container–closure system provides several practical advantages, including convenience
in simplified drug administration; greater accuracy in filling (i.e., less likelihood of overfilling, which is common in other
packaging–delivery options); and reduced instances of misidentification, improper dosing, and contamination (1). These advantages,
along with a critical mass of commercially available syringe systems, have fueled a rapid expansion of the market for prefilled
syringes, with worldwide sales estimated to exceed 1 billion units and annual sales expected to grow at a rate in excess of
10% (2, 3).
The basic components of a prefilled syringe are illustrated in Figure 1. The syringe barrel is typically either made from
Type 1 borosilicate glass or various plastic materials (e.g., polypropylene, cyclic olefin polymer, cyclic olefin copolymers).
Other components (e.g., tip cap and plunger) are typically made from elastomeric materials, which may be surface coated. Syringe
barrels and plungers are typically coated with an agent (e.g., silicone oil) to facilitate plunger movement. Plunger movement
is accomplished by an attached piston rod (typically plastic).
In the US Food and Drug Administration's Guidance for Industry, Container Closure Systems for Packaging Human Drugs and Biologics
http://www.tinyurl.com/28fxgm, the agency defines a container–closure system as "the sum of packaging components that together contain and protect the
dosage form. This includes primary packaging components" (4). A similar definition is provided by the
European Medicines Agency in its Guideline on Plastic Packaging Materials
http://www.emea.europa.eu/pdfs/human/qwp/435903en.pdf (5). It is clear from these definitions that a prefilled syringe meets the definition of a container–closure system and thus
is subject to the associated guidelines and regulations. It is noteworthy that because of its use and nature, a prefilled
syringe, as an injectable product, falls into FDA's highest risk category for the likelihood of a packaging component–dosage
Foremost among these regulations and guidelines are the regulatory expectations that revolve around suitability for the intended
use. As noted in FDA's container–closure guidance:
Every packaging system should be shown to be suitable for its intended use: it should adequately protect the dosage form;
it should be compatible with the dosage form; and it should be composed of materials that are considered safe for use with
the dosage form and the route of administration. If the packaging system has a performance feature in addition to containing
the product, the assembled container closure system should be shown to function properly.
Each of these aspects of suitability for intended use will be considered in greater detail as follows.
As a packaging system, a prefilled syringe must meet all the suitability-for-intended-use expectations. Only certain aspects
of a given expectation may be applicable to prefilled syringes. For example, the expectation of protection of the dosage form
is interpreted to mean that the prefilled syringe should protect the dosage form from factors that may degrade the quality
of the dosage form throughout its shelf life. Some commonly cited causes of such degradation for prefilled syringes include
loss of solvent, adsorption of water vapor, and microbial contamination. Other potential causes of degradation, including
light exposure and contact with reactive gases, are less germane to mainstream applications of prefilled syringes because
such systems are not currently marketed as light or gas barriers.