Secondary and Tertiary Packaging Leachables: Why Non-Contact Components Still Migrate Into Your Drug

Introduction

Secondary and tertiary packaging leachables are volatile, semi-volatile, or mobile chemical substances that originate from non-contact outer packaging materials, including printing inks, adhesives, varnishes, corrugated shippers, and labels. These substances can migrate across semi-permeable primary containment systems and enter pharmaceutical formulations. Even without direct liquid contact, chemical constituents can cross physical barriers through vapor-phase outgassing, mechanical set-off during converting, and ambient diffusion processes. This cross-barrier migration challenges the traditional assumption that non-contact packaging materials do not pose a risk to drug product quality. Low-molecular-weight additives present in outer paperboard cartons and shipping containers can readily pass through primary polymeric containers, potentially causing chemical contamination, active pharmaceutical ingredient (API) degradation, and toxicological concerns.

Global regulatory authorities, including the U.S. Food and Drug Administration (FDA), European Medicines Agency (EMA), and Health Canada, require a risk-based assessment of the entire packaging system. When volatile organic compounds outgas from secondary labels or tertiary corrugated boxes, they accumulate in the secondary packaging headspace. This creates a chemical potential gradient that promotes cross-barrier diffusion. Advanced analytical testing conducted by specialized laboratories, such as ResolveMass Laboratories Inc., has demonstrated that non-contact leachables can exceed regulatory Analytical Evaluation Thresholds (AET). Such findings necessitate comprehensive chemical characterization, root-cause investigation, and toxicological safety assessments.

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Quick Summary:

• What they are: Secondary and tertiary packaging leachables are chemicals from non-contact packaging, like carton inks, label adhesives and corrugated shippers. They can still get into the drug by passing through semi-permeable primary containers.
• How they migrate: There are three main routes. Chemicals outgas as vapor and permeate the container wall, transfer by set-off during printing and stacking, or diffuse faster at higher temperature and humidity.
• Key contaminants: These include UV ink photoinitiators (benzophenone, ITX) and MOSH/MOAH mineral oils from recycled board. Adhesive solvents, phthalates and BHT by-products also contribute.
• Products most at risk: Parenterals and IV bags, especially surfactant-containing biologics, are most exposed. LDPE eye drops, lyophilized cakes that adsorb vapors, and inhaled products are also at risk.
• Regulatory expectations: USP, FDA, EMA and Health Canada expect the whole packaging system to be assessed. Leachables are judged against a Safety Concern Threshold of 1.5 µg/day, and any compound above the Analytical Evaluation Threshold must be identified and evaluated.
• Testing approach: Headspace GC-MS covers volatiles, GC-MS covers semi-volatiles, and LC-HRAM-MS covers non-volatiles. GC-FID/HPLC-FLD measures mineral oils and ICP-MS measures metals.
• Risk mitigation: Use low-migration or EB-cured inks, virgin pulp board and solvent-free adhesives. Add barriers such as foil overpouches or EVOH/SiOx coatings, and switch from LDPE to COP/COC containers.

Migration Mechanisms of Secondary and Tertiary Packaging Leachables

The migration of secondary and tertiary packaging leachables primarily occurs through three distinct physical processes: vapor-phase outgassing followed by cross-barrier permeation, mechanical set-off transfer during converting, and thermally accelerated Arrhenius diffusion. These migration pathways allow low-molecular-weight additives present in external cardboard, labels, and shipping containers to enter primary packaging systems without requiring direct contact with the pharmaceutical formulation.

Vapor-Phase Outgassing and Permeation

Vapor-phase permeation is the principal mechanism through which volatile and semi-volatile organic compounds (VOCs and SVOCs) originating from non-contact packaging materials contaminate pharmaceutical formulations. Secondary printed cartons, varnishes, corrugated shipping containers, and labeling adhesives continuously release volatile molecules into the microenvironment of the package headspace. Semi-permeable primary containers, including Low-Density Polyethylene (LDPE), Polypropylene (PP), Polyvinyl Chloride (PVC), and thin elastomeric closures, function as selective membranes rather than completely impermeable chemical barriers.

Mass transport through the wall of a semi-permeable polymeric container is governed by Fick’s laws of diffusion in combination with Henry’s law of solubility. The overall mass flux (J) across the barrier film depends on the migrant’s solubility coefficient (S) within the polymer matrix, its diffusion coefficient (D), the concentration gradient (ΔC) across the barrier, and the thickness (x) of the primary container:

J = −D × (∂C/∂x)

The overall migration process follows a multi-stage thermodynamic sequence:

1. Organic compounds are released from secondary paperboard or tertiary corrugated packaging matrices into the internal secondary packaging headspace.
2. The gas-phase migrant subsequently adsorbs onto the external surface of the primary polymeric container wall.
3. The migrant dissolves into the bulk polymer matrix according to its thermodynamic partition coefficient.
4. The molecule travels through the amorphous regions of the primary polymer wall along the concentration gradient.
5. Finally, the migrant desorbs from the inner container wall and enters the liquid formulation or vial headspace.

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Set-Off Migration During Converting and Storage

Set-off migration refers to the physical transfer of chemical substances from a printed outer surface to an unprinted inner surface during roll-winding, stacking, or converting operations. During high-speed printing of secondary folding cartons, foil overwraps, and blister lidding materials, the printed outer surface is pressed against the unprinted contact surface under considerable pressure while the materials are stored on reels. Under these conditions, uncured printing inks, photoinitiators, lacquers, and residual solvents can transfer directly onto the opposite unprinted surface.

When these converted materials are subsequently shaped into secondary cartons or pouches, the contaminated inner surface faces the primary drug container. The transferred chemical compounds can then outgas across the narrow internal air gap. This process reduces the distance required for vapor transport and allows the migrants to penetrate the primary packaging wall more rapidly.

Arrhenius Diffusion Kinetics and Environmental Acceleration

The rate of chemical migration through semi-permeable primary containment systems increases exponentially with temperature, following Arrhenius kinetics. Higher temperatures supply additional thermal energy, increasing polymer free volume and the kinetic energy of migrating molecules. The temperature-dependent behavior of the diffusion coefficient (D) can be represented by the following equation:

D = D₀ × exp(−E_a / (R × T))

Here, D₀ represents the pre-exponential factor, E_a is the activation energy for diffusion, R denotes the universal gas constant, and T represents the absolute temperature. Accelerated stability conditions (40°C / 75% RH) can substantially increase cross-barrier diffusion rates, leading to faster leachable accumulation. Furthermore, elevated humidity can plasticize hydrophilic polymers, increasing the spacing between polymer chains and facilitating molecular transport into the drug product.

Volatile and Semi-Volatile Contaminants in Secondary and Tertiary Packaging Leachables

The major chemical classes associated with secondary and tertiary packaging leachables include ultraviolet (UV) ink photoinitiators, mineral oil saturated and aromatic hydrocarbons (MOSH/MOAH), ester plasticizers, and volatile adhesive residues. These low-molecular-weight compounds generally exhibit relatively high vapor pressures or elevated octanol-water partition coefficients (K_ow). These properties promote their volatilization and subsequent partitioning across primary container walls.

Ultraviolet (UV) Cured Ink Photoinitiators

Photoinitiators are chemical additives incorporated into UV-curable inks and lacquers to initiate and accelerate polymerization when exposed to ultraviolet light during folding carton printing. Inadequate UV curing can leave residual, unreacted photoinitiators within the ink layer. Since many of these compounds have molecular weights below 300 Da, they can readily outgas and permeate semi-permeable primary packaging barriers.

• Benzophenone (C₁₃H₁₀O) and 4-Methylbenzophenone (C₁₄H₁₂O): Benzophenone is a mobile aromatic photoinitiator that can migrate from printed folding cartons through outgassing. It can penetrate plastic containers through gas-phase transport and partition into both aqueous and lipophilic formulations, potentially creating endocrine-disrupting hazards.
• 2-Isopropylthioxanthone (ITX, C₁₆H₁₄OS): ITX is a hydrophobic photoinitiator capable of migrating from printed secondary packaging through outgassing. Its lipophilic chemical structure promotes partitioning into lipid emulsions, parenteral formulations, and surfactant-stabilized biologics.
• Ethyl-4-(dimethylamino)benzoate (EDAB) and Amine Synergists: Amine co-initiators can produce volatile degradation products that modify formulation pH or interact directly with sensitive active pharmaceutical ingredients.

Mineral Oil Saturated Hydrocarbons (MOSH) and Mineral Oil Aromatic Hydrocarbons (MOAH)

Recycled paperboard used in secondary cartons and tertiary shipping containers can contain considerable quantities of mineral oil hydrocarbons originating from newsprint inks and industrial processing lubricants. These complex hydrocarbon mixtures are generally divided into two categories:

• Mineral Oil Saturated Hydrocarbons (MOSH): These compounds consist of open-chain paraffinic and cyclic naphthenic hydrocarbons (C₁₀ to C₅₀). MOSH fractions within the C₁₀ to C₂₅ range possess sufficient volatility to migrate through the gas phase at room temperature, potentially penetrating plastic ampoules and blister packs. Certain short-chain MOSH compounds can accumulate in human lymphoid tissue, the liver, and the spleen.
• Mineral Oil Aromatic Hydrocarbons (MOAH): These substances consist of alkylated polycyclic aromatic hydrocarbons. MOAH fractions containing three to seven fused aromatic rings are associated with genotoxic and carcinogenic concerns. Outgassing of MOAH from tertiary corrugated shipping containers during transportation can therefore create a significant contamination risk during long-term drug product storage.

Adhesives, Tackifiers, and Solvent Residues

Cold-seal and hot-melt adhesives used in carton side seams, shipping labels, and tamper-evident seals can release volatile organic chemicals into the packaging environment. Important migrants associated with synthetic adhesives include residual solvents such as toluene, ethyl acetate, and cyclohexane; phthalate plasticizers, including diisobutyl phthalate (DIBP) and dibutyl phthalate (DBP); tackifying rosin esters; and antioxidant degradation products, such as 2,6-di-tert-butyl-4-methylphenol (BHT) quinones.

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Risk Profiles of Dosage Forms Exposed to Secondary and Tertiary Packaging Leachables

The susceptibility of pharmaceutical dosage forms to secondary and tertiary packaging leachables varies according to their physical state, vehicle lipophilicity, surface area-to-volume ratio, and route of administration. Formulations considered particularly vulnerable include parenterals containing surfactant co-solvents, Low-Density Polyethylene (LDPE) ophthalmic solutions, and highly porous lyophilized cakes.

Parenterals and Large-Volume Intravenous Solutions

Parenteral formulations administered through intravenous, intramuscular, or subcutaneous routes bypass the protective metabolic barriers of the gastrointestinal tract, making potential contamination a significant clinical safety concern. Large-volume parenterals (LVP) packaged in flexible polyolefin or PVC bags are frequently enclosed in secondary protective overpouches. Solvent residues, plasticizers, and printing ink photoinitiators originating from the outer printed pouch or label can permeate through the relatively thin primary bag wall and enter the sterile fluid.

Biologic products containing non-ionic surfactants, such as Polysorbate 20 or Polysorbate 80, are particularly susceptible to this type of contamination. Surfactant micelles reduce formulation surface tension and can encapsulate non-polar migrants, including photoinitiators and BHT. This behavior can increase the apparent solubility of these substances in the formulation and facilitate their migration across packaging barriers.

Ophthalmic Drug Products

Ophthalmic solutions are commonly packaged in Low-Density Polyethylene (LDPE) blow-fill-seal (BFS) bottles or dropper containers. Because LDPE has relatively low density and substantial polymer free volume, it exhibits considerable permeability to organic vapors. When LDPE ophthalmic bottles are stored inside printed secondary paperboard cartons or fitted with labels containing pressure-sensitive adhesives, volatile photoinitiators, such as Benzophenone, and adhesive tackifiers can outgas and migrate through the LDPE wall. These substances may subsequently dissolve in the sterile ophthalmic solution, creating potential risks of localized ocular toxicity.

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Lyophilized Powders and Sterile Crystalline Solids

Solid dosage forms are generally considered less susceptible to leaching because they do not contain a liquid solvent. However, lyophilized (freeze-dried) cakes and sterile active pharmaceutical ingredient (API) powders represent important exceptions. Lyophilized cakes have a high specific surface area and extremely low moisture content, making them effective physical adsorbents for airborne organic vapors.

Volatile compounds released from secondary cartons or tertiary corrugated shipping boxes can diffuse into the vial headspace during prolonged storage. The dry lyophilized cake may then adsorb these volatile organic compounds directly onto its porous matrix. When the product is reconstituted with a liquid diluent before administration, the adsorbed leachables can dissolve into the liquid, introducing chemical impurities into the reconstituted solution.

Regulatory Standards Governing Secondary and Tertiary Packaging Leachables

Global regulatory frameworks established by the USP, FDA, EMA, and Health Canada require comprehensive characterization of both contact and non-contact packaging components to establish the safety of the overall container closure system. Compendial standards emphasize controlled extraction studies, real-time leachable monitoring, and toxicological assessments against established threshold limits.

Enforceable and Informational USP Chapters

The United States Pharmacopeia establishes different regulatory expectations for enforceable compendial chapters (below 1000) and informational risk-management chapters (above 1000):

• USP Packaging and Storage Requirements: Establishes formal definitions and requirements for primary, secondary, and tertiary packaging components. It also outlines functional expectations for protecting pharmaceutical products against atmospheric ingress and chemical contamination.
• USP and Plastic Packaging Systems: Describe characterization requirements, resin testing procedures, and safety assessments for plastic materials used in pharmaceutical packaging systems.
• USP Polymeric Components Used in Manufacturing: Establishes extractables testing approaches for polymeric manufacturing equipment, single-use systems, and secondary process tubing.
• USP Assessment of Extractables Associated with Pharmaceutical Packaging/Delivery Systems: Provides methodologies for Controlled Extraction Studies (CES). These studies involve exposing packaging components to aggressive solvents under elevated thermal conditions to generate a comprehensive chemical profile of potential extractables.
• USP and Assessment of Drug Product Leachables: Describe analytical approaches for monitoring leachable migration into pharmaceutical formulations during real-time shelf-life stability studies. These frameworks require consideration of secondary packaging contributions whenever primary packaging materials exhibit semi-permeable characteristics.

Safety Concern Thresholds (SCT) and Analytical Evaluation Threshold (AET)

The Product Quality Research Institute (PQRI) and USP frameworks establish toxicological safety thresholds that determine the analytical reporting requirements for leachable compounds:

Safety Concern Threshold (SCT): The standardized SCT for organic leachables in parenteral and ophthalmic drug products is established at 1.5 µg/day for total daily intake. Compounds present below the SCT generally represent a lower level of toxicological concern, although specific high-potency mutagenic classes, such as N-nitrosamines and MOAH, require separate consideration.

Analytical Evaluation Threshold (AET): The AET represents the calculated concentration threshold at or above which an analytical chemist must report, identify, and toxicologically evaluate a leachable compound. Its calculation considers the SCT, maximum daily dose (MDD), total fill volume (V), and number of doses per container (N_doses):

AET = (SCT / MDD) × (V / Dose Volume) × (1 / UF)

In this equation, UF represents an Uncertainty Factor, typically ranging from 1.0 to 2.0. This factor accounts for variations in analytical response factors across different chemical classes.

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Analytical Methodologies for Profiling Secondary and Tertiary Packaging Leachables

Reliable characterization of secondary and tertiary packaging leachables requires high-resolution, hyphenated analytical techniques capable of detecting and identifying trace organic compounds at concentrations as low as parts-per-billion (ppb). Standard analytical workflows generally combine Headspace and Direct Injection Gas Chromatography-Mass Spectrometry (GC-MS) with Ultra-High Performance Liquid Chromatography-High Resolution Accurate Mass Spectrometry (UHPLC-HRAM-MS).

Gas Chromatography-Mass Spectrometry (GC-MS) Workflows

Gas chromatography is a primary analytical technique for separating and identifying volatile and semi-volatile migrants originating from secondary packaging inks, adhesives, and tertiary corrugated packaging materials. Common analytical approaches include:

• Headspace GC-MS (HS-GC-MS): This technique is used to identify and quantify volatile organic compounds (VOCs) released into the packaging headspace. HS-GC-MS is suitable for measuring residual printing solvents, including toluene, isopropyl alcohol, and ethyl acetate, as well as low-boiling monomeric residues and volatile adhesive fragments.
• Direct Injection GC-MS: This approach is used to examine semi-volatile organic compounds (SVOCs) extracted from secondary packaging components or detected in stability testing samples. Direct injection GC-MS can identify semi-volatile photoinitiators, such as Benzophenone and ITX, plasticizers, including phthalates, and antioxidant degradation products, such as BHT. Electron Ionization (EI), combined with NIST spectral database matching, supports the structural identification of these compounds.

Liquid Chromatography High-Resolution Accurate Mass Spectrometry (LC-HRAM-MS)

Non-volatile organic compounds (NVOCs), thermally labile photoinitiators, oligomeric additives, and complex secondary degradation products require Liquid Chromatography coupled with High-Resolution Accurate Mass Spectrometry. Commonly used platforms include Orbitrap and Quadrupole Time-of-Flight instruments.

LC-HRAM-MS systems deliver sub-parts-per-million (ppm) mass accuracy, supporting the precise determination of empirical molecular formulas (C_xH_yO_zN_w) for unidentified migrants. Subsequent tandem mass spectrometry fragmentation (MS/MS) provides additional structural information, allowing analytical scientists at ResolveMass Laboratories Inc. to investigate unknown chemical structures and distinguish secondary packaging migrants from active drug degradation pathways.

Sample preparation typically begins with controlled extraction or the isolation of stability testing samples, followed by parallel chromatographic separation. GC-MS is used to investigate volatile and semi-volatile compounds through headspace or direct injection techniques, whereas UHPLC-HRAM-MS separates and characterizes non-volatile chemical species. The resulting spectral signals are compared with NIST libraries and accurate mass databases to determine chemical structures. Identified compounds are then quantified against calculated AET limits to support comprehensive toxicological risk assessments.

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Analytical Testing Matrix for Packaging Qualification

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Risk Mitigation Strategies for Secondary and Tertiary Packaging Systems

Successfully controlling risks associated with non-contact leachables requires a Quality by Design (QbD) strategy that combines low-outgassing packaging materials with highly effective functional barrier layers. Removing volatile ink photoinitiators and replacing permeable primary polymers with suitable low-permeability alternatives can significantly reduce or prevent cross-barrier migration before commercial distribution.

Low-Migration Packaging Materials

Risk reduction should begin during the initial selection of packaging materials by incorporating components designed to minimize chemical outgassing and migration.

• Low-Migration Inks and Polymeric Photoinitiators: Packaging specifications should prioritize low-migration ink formulations that replace monomeric photoinitiators with polymeric alternatives. Polymeric photoinitiators incorporate multiple photoactive functional groups into a high-molecular-weight polymer chain (>1000 Da). Their larger molecular structures reduce volatilization and cross-barrier diffusion. Electron-beam (EB) cured inks offer another effective approach because they undergo polymerization without requiring photoinitiators, thereby eliminating photoinitiator migration risks.
• Virgin Pulp Paperboard: Replacing recycled paperboard with virgin fiber board helps eliminate MOSH and MOAH mineral oil contaminants associated with recycled materials. This substitution reduces the possibility of mineral oil outgassing from secondary cartons during warehouse storage.
• Solvent-Free Adhesive Formulations: Substituting solvent-based adhesives with hot-melt polyolefins or water-borne acrylic adhesives helps prevent residual aromatic solvents from being released into the packaging environment. This approach reduces potential outgassing from secondary labels and carton seams.

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Functional Barrier Integration

A functional barrier refers to a packaging layer designed to prevent extractable chemical substances from migrating across packaging materials and entering the drug formulation throughout its intended commercial shelf life.

• Aluminum Foil Overpouches: High-integrity aluminum foil laminates (>9 µm thickness) provide highly effective barrier protection against organic vapors, light, and moisture ingress. Their incorporation can substantially limit the migration of external contaminants into primary packaging.
• High-Barrier Co-Extrusions: Integrating Ethylene Vinyl Alcohol (EVOH), Silicon Oxide (SiO_x), or Aluminum Oxide (Al₂O₃) barrier coatings into secondary plastic films can significantly reduce VOC permeation rates and improve overall packaging protection.
• Polymeric Barrier Substitution: Replacing highly permeable LDPE primary containers with lower-permeability alternatives, including Cyclic Olefin Polymers (COP) and Cyclic Olefin Copolymers (COC), can reduce the absorption of gas-phase leachables and limit their migration into pharmaceutical formulations.

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Conclusion

Managing secondary and tertiary packaging leachables is critical to preserving drug product safety, therapeutic potency, and regulatory submission readiness. Non-contact packaging components can introduce significant chemical contamination risks through gas-phase permeation, set-off transfer, and solvent-mediated diffusion. Therefore, comprehensive testing of the entire container closure system is necessary to identify and control potential sources of contamination.

By selecting low-migration packaging materials, incorporating effective functional barriers, and conducting rigorous testing in accordance with applicable USP and related regulatory requirements, pharmaceutical manufacturers can maintain container closure integrity throughout the commercial product lifecycle. Collaborating with specialized analytical testing laboratories further supports regulatory compliance, helps prevent costly filing delays, and protects patient health. Comprehensive extractables and leachables assessments also provide valuable information for identifying potential chemical interactions between packaging components and pharmaceutical formulations before products reach the market.

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To discuss your packaging system qualification and extractable/leachable testing requirements, contact the analytical team at ResolveMass Laboratories Inc. through their contact portal.

Frequently Asked Questions (FAQs)

Reference:

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Anusha Sinha