Cartridge Compatibility and Primary Container Integration: A Comprehensive Technical Guide for Pen Injector Manufacturers
Introduction
At the heart of every pen injector lies a critical component that often determines the success or failure of the entire drug delivery system: the primary container. Whether it is a glass cartridge or an advanced polymer alternative, the primary container serves as the direct interface between the drug product and the patient—a role that demands uncompromising precision, compatibility, and reliability.
The pharmaceutical cartridges market is experiencing robust growth, valued at approximately USD 2.48 billion in 2025 and projected to reach USD 2.73 billion in 2026, representing a compound annual growth rate of 10.0%. The global fill-finish cartridge market is even more impressive, valued at USD 2.5 billion in 2024 and projected to reach USD 4.9 billion by 2030, growing at a CAGR of 11.9%. This explosive growth is driven by the expansion of biologic therapies, the increasing adoption of patient-friendly self-administration devices, and the growing demand for pre-filled and dual-chamber cartridge systems.
For pharmaceutical manufacturers and packaging professionals, understanding the intricate relationship between cartridge compatibility and primary container integration is essential—not only for regulatory compliance but for ensuring patient safety, drug stability, and commercial success. This comprehensive technical guide explores the critical aspects of cartridge selection, compatibility assessment, and integration into pen injector systems.
At Vialab Pharmaceutical Packaging Co., Ltd. , we specialize in the design and manufacture of high-quality drug delivery and packaging components. From injection pens (disposable and reusable) to glass vials, sterile vials, and aluminum caps, every product is engineered to meet strict pharmaceutical standards. With advanced production lines and cleanroom facilities, we ensure consistent quality, integrity, and compliance for global healthcare partners.
1. Understanding the Primary Container in Pen Injector Systems
What is a Primary Container?
In the context of pen injectors, the primary container—typically a cartridge—is the component that directly contains the drug product. It serves as the sterile barrier between the medication and the external environment, maintaining drug stability and integrity throughout the product’s shelf life and during administration.
ISO 11608-3 defines the primary container as a “container either filled by the manufacturer (primary container closure) or by the end-user (reservoir)”. This encompasses both pre-filled cartridges supplied as finished drug products and user-filled cartridges that patients load themselves.
The Cartridge as a Critical System Component
The cartridge is not merely a passive container—it is an active participant in the drug delivery system. It must:
- Maintain drug stability throughout the product’s shelf life
- Withstand mechanical stresses during shipping, storage, and handling
- Enable accurate dosing through precise dimensional tolerances
- Ensure secure needle attachment and leak-proof sealing
- Support container closure integrity (CCI) to maintain sterility
2. Material Selection: Glass vs. Polymer Cartridges
Glass Cartridges: The Established Standard
Borosilicate glass has been the gold standard for pharmaceutical cartridges for over a century. In 2024, the glass materials segment held a 52.4% market share. Glass continues to be widely used in legacy injectable therapies and traditional insulin cartridges.
Key advantages of glass cartridges include:
- Proven compatibility with a wide range of drug formulations
- Excellent barrier properties against moisture and oxygen
- Low extractables and leachables profile
- Regulatory acceptance and established manufacturing infrastructure
- Superior chemical resistance to a wide range of injectable drugs
ISO 13926-1 specifies the design, materials, performance, test methods, and dimensional recommendations for glass cylinders used in cartridge-type needle-based injection systems for medical use. The current version, ISO 13926-1:2018, continues to serve as the foundational standard for glass cartridge manufacturing.
At Vialab, we continue to offer glass vials and tubes in parenteral grade with precise dimensions, recognizing that glass remains essential for many legacy therapies and traditional applications. Our glass cartridges are manufactured to meet the stringent requirements of ISO 13926-1, ensuring dimensional accuracy and consistent quality.
Polymer Cartridges: The Emerging Alternative
The industry is increasingly moving away from glass due to its susceptibility to breakage, higher weight, and lower compatibility with sensitive compounds, especially in modern biologic therapies. Polymer technologies, particularly Cyclic Olefin Copolymer (COC) and Cyclic Olefin Polymer (COP), are gaining significant traction.
The global cyclic olefin polymer market is valued at approximately USD 1.34 billion in 2025 and is projected to grow at a CAGR of 6.8% to reach USD 2.42 billion by 2034.
Key advantages of polymer cartridges include:
- Break resistance: Polymer cartridges are much less likely to fracture during manufacturing, shipping, or use
- Design flexibility: Unlike glass with limitations in shaping and tolerance control, COC can be molded into complex, integrated forms with tight dimensional accuracy
- Reduced contamination risk: Polymeric primary drug containers resolve many known issues with glass
- Ultra-high purity: Engineered polymers like ZEONEX COP offer extremely low off-gas and leachable content
- Inert surface: Minimizes protein adsorption, making it ideal for sensitive biologics
SCHOTT Pharma recently launched the industry’s first ready-to-use (RTU) polymer cartridge that complies with ISO dimensions. Made from Cyclic Olefin Copolymer (COC), the cartridge features a homogenous, cross-linked siliconization layer that minimizes protein adsorption, provides low levels of extractables and leachables, and ensures consistent break-loose and gliding forces throughout the product’s shelf life.
The polymer cartridge delivers functional performance comparable to glass, with added break resistance. Produced using advanced injection molding technology, it offers exceptional dimensional accuracy and allows for customization. Available in 1.5 ml, 3 ml, and 5 ml formats (with a 10 ml version in development), the cartridge is compatible with all major fill-and-finish lines.
Material Comparison Summary
| Factor | Glass Cartridges | Polymer Cartridges |
|---|---|---|
| Break Resistance | Susceptible to breakage | Highly resistant |
| Design Flexibility | Limited shaping capabilities | Complex, integrated designs |
| Dimensional Tolerances | Standard | Exceptionally tight |
| Extractables/Leachables | Low | Extremely low |
| Protein Adsorption | Moderate | Minimized |
| Regulatory Acceptance | Established | Growing |
| Market Share (2024) | 52.4% | Growing rapidly |
3. Cartridge Compatibility: A Multi-Dimensional Challenge
Dimensional Compatibility
The most fundamental aspect of cartridge compatibility is dimensional fit. The cartridge must interface seamlessly with the pen injector’s mechanical systems, including:
- Outer diameter: Must match the pen body’s internal dimensions
- Flange geometry: Critical for secure seating and proper alignment
- Cone dimensions: Essential for needle attachment and fluid path integrity
- Neck finish: Must accommodate the pen needle hub
Tight tolerances in the cone and flange areas enhance adaptability to a wide range of injection devices. Even minor dimensional deviations can compromise dose accuracy, seal integrity, or device functionality.
Mechanical Compatibility
The cartridge must withstand the mechanical forces encountered during:
- Insertion into the pen body
- Piercing by the pen needle (for multi-pierce applications)
- Plunger advancement during dose delivery
- Dropping and vibration during shipping and handling
Gerresheimer and Midas Pharma have developed a novel cartridge-based autoinjector concept in which the cartridge as primary packaging is under constant pressure. This highlights the importance of understanding how cartridge materials behave under long-term mechanical stress.
Functional Compatibility
The cartridge must enable accurate and consistent drug delivery through:
- Container closure integrity (CCI) : Maintaining the sterile barrier
- Plunger movement: Consistent break-loose and gliding forces
- Needle penetration: Ensuring proper piercing without coring
- Dose accuracy: Precise volume delivery within allowable limits
USP Chapter <1207> provides scientific guidance for assessing the integrity of pharmaceutical container closure systems. The chapter specifies deterministic test methods for container closure integrity testing, including high voltage leak detection for cartridges.
Drug Compatibility
Perhaps the most critical aspect is compatibility with the drug formulation itself. Container selection and compatibility studies are integral to ensuring biologic product stability. Key considerations include:
- Chemical compatibility: No interaction between drug and container materials
- Adsorption: Minimizing protein or API adsorption to container surfaces
- Extractables and leachables: Ensuring levels are within acceptable limits
- Stability: Maintaining drug potency and purity throughout shelf life
SCHOTT TOPPAC® polymer cartridge is particularly suitable for sensitive biologics, including cell and gene therapies, biosimilars, and emergency drugs. The inert surface minimizes protein adsorption and provides low levels of extractables and leachables.
4. Regulatory Framework: ISO 11608-3 and Beyond
ISO 11608-3: Containers and Integrated Fluid Paths
ISO 11608-3 specifies requirements and test methods for the design verification of containers and integrated fluid paths used with Needle-Based Injection Systems (NISs) according to ISO 11608-1. It is applicable to single and multi-dose containers either filled by the manufacturer (primary container closure) or by the end-user (reservoir), such as cartridges.
The current version, ISO 11608-3:2022, has been updated to include integrated fluid paths as well as finished containers. An amendment, ISO 11608-3:2022/Amd 1:2026, is currently under development, reflecting the ongoing evolution of the standard.
Key requirements of ISO 11608-3 include:
- Design verification of containers and integrated fluid paths
- Performance testing under various conditions
- Functional stability testing for reusable systems
- Risk-based design approaches
ISO 13926-1: Glass Cylinders for Cartridge-Type NIS
ISO 13926-1 specifies the design, materials, performance, test methods, and dimensional recommendations for glass cylinders used in cartridge-type needle-based injection systems for medical use. The standard is currently under revision, with ISO/DIS 13926-1:2025 in development.
USP Standards for Container Closure Integrity
USP <382> , implemented in December 2025, marks the most consequential regulatory change to functional suitability requirements for elastomeric container closure systems. Key aspects include:
- Shift from component-level testing to system-level fitness-for-intended-use testing
- Container closure integrity (CCI) testing per USP <1207>
- Functional requirements for closures in pre-filled syringes, cartridges, and pens
USP <1207> provides the most thorough guidance on CCI concepts for sterile and critical products. It states a preference for deterministic tests that are non-invasive, produce repeatable and predictable results, and are suited to 100% testing.
FDA Requirements for Combination Products
The FDA treats pen injectors and drugs as combination products, requiring complete validation data on safety and effectiveness. The pen injector is considered secondary packaging because it is not in primary contact with the parenteral product. However, the cartridge—as the primary sterile barrier—is subject to rigorous CCI requirements.
5. Integrated Fluid Paths: The Evolution of Cartridge Systems
The 2022 revision of ISO 11608-3 introduced the concept of integrated fluid paths, expanding the scope beyond traditional containers. An integrated fluid path refers to the complete fluid pathway from the cartridge through the needle or cannula to the patient.
This evolution reflects the increasing complexity of drug delivery systems, which now include:
- Rigid needles integrated with the cartridge
- Soft cannulas for extended wear applications
- Fluid line connections between cartridge and delivery site
- On-body delivery systems with integrated fluid paths
The complete fluid circuit must be verified for design, performance, and safety. This requires a holistic approach to cartridge compatibility that considers not just the container itself but the entire fluid pathway.
6. Emerging Trends in Cartridge Technology
Pre-Filled and Dual-Chamber Cartridges
Major trends in the pharmaceutical cartridges market include rising demand for pre-filled and dual-chamber cartridges. Dual-chamber cartridges are particularly important for:
- Lyophilized drugs requiring reconstitution before administration
- Combination therapies requiring separate storage of active ingredients
- Sensitive biologics requiring protection from degradation
The global dual chamber cartridges market is expected to grow at a CAGR of 7.8%, reaching USD 2.52 billion by 2033.
Customization and Patient-Centric Design
There is a growing focus on customizable cartridges for specialized pharmaceutical needs. This includes:
- Overfill geometry to reduce variability in fill volumes and minimize drug waste
- Tight dimensional tolerances for enhanced device compatibility
- Patient-friendly features for easier self-administration
Sustainability
Environmental concerns are driving innovation in cartridge materials and designs:
- Reduced material usage through optimized designs
- Recyclable materials for polymer cartridges
- Reduced breakage minimizing drug waste and safety hazards
7. Practical Recommendations for Manufacturers
For Cartridge Selection
- Conduct comprehensive compatibility studies early in product development
- Evaluate both glass and polymer options based on drug requirements
- Consider dimensional tolerances and their impact on device performance
- Assess mechanical compatibility under real-world conditions
- Verify container closure integrity using deterministic test methods
For Cartridge Integration
- Integrate compliance early in product design, not only during final testing
- Establish Quality Management Systems aligned with ISO 13485
- Choose suppliers with proven medical-grade validation and compliance track records
- Document all test methods, validation, and results as part of your technical compliance file
Conclusion
Cartridge compatibility and primary container integration represent the foundation of successful pen injector development. The choice between glass and polymer cartridges involves complex trade-offs across material properties, dimensional precision, drug compatibility, regulatory compliance, and manufacturing economics.
The regulatory landscape continues to evolve, with ISO 11608-3 establishing requirements for design verification of containers and integrated fluid paths, ISO 13926-1 specifying dimensional standards for glass cartridges, and USP <382> introducing new functional suitability requirements for elastomeric closures.
At Vialab Pharmaceutical Packaging Co., Ltd. , we bring decades of expertise in pharmaceutical packaging and drug delivery components to support our partners through every stage of the cartridge selection and integration process. From injection pens (disposable and reusable) and glass vials to sterile vials and aluminum caps, our comprehensive product portfolio and commitment to quality ensure that your drug delivery system meets the highest standards of safety, reliability, and patient satisfaction.
Whether you are developing a new biologic therapy, transitioning between glass and polymer cartridge platforms, or seeking to enhance your existing product line, our team of packaging experts is ready to provide the technical guidance and manufacturing excellence you need to succeed in this rapidly evolving market.
Contact Vialab Pharmaceutical Packaging Co., Ltd. today to discuss your cartridge and primary container requirements and discover how our precision pharmaceutical packaging solutions can support your next product launch.