Extractables are chemical entities that migrate out of a material under exaggerated laboratory extraction conditions, while leachables are the subset of those entities that actually migrate into a drug product during normal storage and use. Because leachables carry direct implications for patient safety and product stability, materials should be screened early and tested against an Analytical Evaluation Threshold and Safety Concern Threshold derived under ICH Q3E, with dossier evidence structured to satisfy Therapeutic Goods Administration expectations.
Definitions and fundamental concepts
Extractables are chemical species released from packaging, container closure systems, single-use manufacturing components or delivery device materials when those materials are subjected to solvents, elevated temperatures or extended contact times that exceed conditions the product would ever experience in practice. Leachables are the compounds that transfer into the drug product itself under labelled storage and use conditions, and according to a review of extractables and leachables in pharmaceutical products, they are generally a subset of the extractables identified during controlled testing, though secondary reactions and material ageing can generate additional leachables not predicted by the original extractables profile, including compounds formed through ultraviolet exposure, heat or oxidative stress.
Several classes of compounds recur across pharmaceutical materials:
- Antioxidants and stabilisers, such as hindered phenols and phosphites added to polymers to resist oxidative degradation.
- Plasticisers, including phthalates and adipates used to impart flexibility to tubing and bags.
- Residual monomers and oligomers left over from incomplete polymerisation reactions.
- Vulcanisation accelerators and curing agents, common in elastomeric closures and stoppers.
- Processing aids, such as slip agents, mould-release compounds and pigments.
The experimental variables that govern how much of a given compound is extracted, and therefore how representative the extractables profile is of eventual leachables, include the surface area to volume ratio (SA:V) of the material relative to the drug product volume, contact duration, and the polarity of the extraction solvent relative to the formulation. A study designed with aggressive solvents and long extraction times at high temperature captures a wide chemical space, but that stringency must be calibrated so the resulting profile remains a useful predictor rather than an exaggerated catalogue unrelated to real product exposure.
Material ageing complicates this picture further. Polymers exposed to ultraviolet light, heat cycling or residual oxygen during storage can undergo secondary reactions that produce degradation products absent from the original unstressed material. A stabiliser package can itself degrade into smaller, more mobile fragments over a product's shelf life, meaning an extractables study performed on fresh material may understate what eventually leaches from an aged container closure system.
Why extractables and leachables matter for safety and product quality
Leachables matter because they represent an uncontrolled, patient-facing exposure pathway distinct from the intended active ingredient, and the toxicological consequences range from irritation and immunogenic reactions to mutagenicity and carcinogenicity, depending on the compound and the dose delivered over a course of treatment. Beyond direct toxicology, leachables can compromise drug product quality by accelerating degradation, altering potency, changing appearance or promoting particulate formation, all of which threaten stability claims made in a marketing dossier.
A leachable's risk classification under ICH Q3E sorts compounds into Class 1, 2 or 3 categories, and Class 1 leachables carry compound-specific limits and should be avoided wherever a formulation or component alternative exists. This classification, together with the route of administration and dosing frequency, determines how conservative the applicable threshold must be: an inhaled or injectable product tolerates far less leachable exposure than an oral solid dose, because the exposure route bypasses first-pass metabolism and reaches systemic circulation more directly.
Route and dosing regimen also affect how thresholds are applied in practice. A product administered daily over years accumulates leachable exposure differently to a single-dose acute treatment, so the same nominal leachable concentration can carry very different risk weightings depending on the treatment duration assumed in the safety case. Programmes that defer leachables testing until late-stage stability studies, rather than screening materials during early development, risk discovering an unacceptable leachable close to a planned submission date, forcing reformulation, re-qualification of container closure systems or renewed stability studies, any of which can add months to a development timeline. Building the AET and SCT calculation into material selection criteria from the outset avoids this pattern by flagging problematic materials before they are locked into a formulation.
Regulatory landscape and guidance for extractables and leachables
Sponsors working through an extractables and leachables programme answer to a small set of interlocking documents rather than a single rulebook, and the practical task is mapping each guidance source to a specific decision point in development. ICH Q3E establishes the risk-based framework at the centre of this landscape, introducing the Analytical Evaluation Threshold and Safety Concern Threshold as the two figures that decide whether a leachable requires reporting and toxicological qualification, and defining potency classes that determine the qualification pathway once a compound is identified.
- ICH Q3E sets the AET and SCT concept, defines Class 1/2/3 potency categories and links to ICH M7 for compounds requiring genotoxicity assessment.
- USP <1663> and <1664> provide compendial study designs for controlled extraction studies and leachables assessment, particularly for orally inhaled and nasal drug products and parenteral products, as detailed on USP's extractables and leachables resource page.
- PQRI perspectives on threshold use recommend progressing from material screening through to formal stability-linked leachables monitoring, informing when toxicological qualification is warranted.
- TGA guidance requires sponsors to identify container materials and provide physicochemical and biological safety evidence within the product dossier.
Where a leachable requires toxicological qualification, ICH M7 governs the genotoxicity assessment pathway, meaning a Class 1 leachable identified during an E&L programme is not just an analytical finding but a trigger for a structured mutagenicity evaluation under a separate but connected guideline.
For submissions to the Australian regulator, sponsors must identify container materials and provide physicochemical and biological safety evidence, and when leachables require toxicological qualification, full study reports or literature references must accompany the submission. Practically, this means the extractables profile, the leachables stability data and any toxicological justification belong together in a single dossier section referenced against the material identification, rather than scattered across separate quality and safety modules where a reviewer would need to cross-reference them manually. Readers managing container material documentation for Australian submissions may find it useful to review packaging material considerations alongside the TGA's own guidance.
Designing extractables studies: controlled extraction best practice
A well-designed extractables study uses a panel of solvents spanning polar and non-polar chemical space, extraction temperatures that reflect a stress condition without becoming chemically unrealistic, and contact times long enough to approach extraction equilibrium for the material under test. The purpose is to generate a profile broad enough to anticipate the leachables a product will encounter over its shelf life, without so overstating extraction conditions that the resulting data become irrelevant to real-world exposure.
- Calculate the surface area to volume ratio for the component being tested relative to the drug product contact volume, since this ratio scales the extractable yield reported per unit of product.
- Select lots representative of production-scale material, because extractables profiles can shift between laboratory-scale and commercial-scale processing of the same nominal polymer grade.
- Test both processed components and unprocessed resin where practical, since evidence from polymer material comparisons shows processed components can differ from raw resin, though resin screening remains a useful early tool for material selection, as demonstrated in a comparison of processed and unprocessed polymer materials.
- Choose solvents that bracket the formulation's own polarity, typically including at least one aqueous, one polar organic and one non-polar organic extraction medium.
- Extract at multiple temperatures, often including an elevated-temperature condition to accelerate release and a condition closer to intended storage to anchor realistic yields.
Resin-level screening can accelerate supplier down-selection early in development, since running a full extractables battery on every candidate component from every supplier is rarely practical within typical development timelines. But resin data cannot universally substitute for testing the finished, processed component, because moulding, sterilisation and assembly steps introduce their own extractable contributions that unprocessed resin does not capture. Any decision to rely on resin-level data as a screening proxy should be documented with the supporting comparison data retained for dossier reference.
The resulting extractables profile then feeds directly into leachables method development. Compounds identified above a defined reporting threshold in the extractables study become target analytes for the leachables method, and the extraction data inform which analytical techniques are needed, whether additional sample preparation is required, and where the AET should be set for the subsequent leachables programme.
Pro Tip: Run extractables studies on at least two independent lots of the candidate material before finalising a supplier, since lot-to-lot variability in additive loading can be larger than the variability introduced by different extraction solvents.
Designing leachables studies and calculating AET and SCT
A leachables study is built around the Analytical Evaluation Threshold, a study-specific reporting level calculated from the maximum daily dose of the drug product and the Safety Concern Threshold that applies to its route of administration, with an uncertainty factor applied to account for analytical and toxicological variability. Any leachable detected above the AET is reported and, depending on its potency classification, may require compound-specific toxicological qualification, as set out in the ICH Q3E framework.
Practical leachables study design follows a sequence of decisions:
- Determine the maximum daily dose of the drug product to anchor the AET calculation, since a higher daily dose lowers the acceptable concentration of any given leachable.
- Select stability timepoints that align with the product's intended shelf life claims, typically including early, intermediate and long-term timepoints under both real-time and accelerated storage conditions.
- Match the sample matrix to the actual drug product, since leachables studies performed on placebo or surrogate matrices can miss interactions specific to the active formulation.
- Apply an uncertainty factor to the SCT-derived AET to account for variability in analytical recovery and in the toxicological database underlying the threshold.
- Escalate to compound-specific toxicology once a leachable is confirmed above the AET and its structure is identified, particularly for Class 1 compounds where avoidance is preferred over qualification.
A leachable detected above the AET but below the SCT still needs to be reported and tracked through stability, while one exceeding the SCT itself moves directly into toxicological risk assessment under ICH Q3E's threshold framework. This distinction matters operationally: AET breaches generate reporting and trending obligations, while SCT breaches generate a qualification workstream that can involve literature-based genotoxicity assessment, in silico QSAR modelling, or dedicated toxicology studies where no adequate literature basis exists.
Matrix effects deserve particular attention for peptide-based drug products administered by injection. Prefilled syringe systems that use pressure-sensitive adhesives or elastomeric plunger components have been shown in the literature to release leachables capable of forming adducts with peptide actives, including acrylic acid and related adhesive-derived compounds detected in prefilled syringe leachables studies. A leachables programme for a peptide product should therefore include the specific container closure and delivery device components in the stability matrix, not just the primary vial or bag, since adduct formation of this kind would not be predicted by testing the drug substance in isolation.
Analytical methods and method validation for E&L testing
Extractables and leachables analysis relies on a small set of complementary analytical techniques, each suited to a different chemical space, and a defensible programme typically applies more than one to cover volatile, semi-volatile, non-volatile and elemental impurities comprehensively.
- Gas chromatography-mass spectrometry (GC-MS) and headspace GC target volatile and semi-volatile organic compounds, including residual solvents and small-molecule degradation products.
- Liquid chromatography-mass spectrometry (LC-MS), including high-resolution mass spectrometry, covers non-volatile organic extractables such as antioxidants, plasticisers and oligomers that GC-based methods cannot resolve.
- Inductively coupled plasma mass spectrometry (ICP-MS) quantifies elemental impurities arising from catalysts, pigments or metal components in contact with the product.
- Orthogonal structure elucidation techniques, including high-resolution mass spectrometry paired with fragmentation software, are used when a spectral library match is insufficient to confirm a compound's identity, an approach demonstrated in analytical workflows for packaging-derived leachables.
Method validation for E&L work follows conventional analytical validation principles but with added emphasis on uncertainty estimation tied back to the AET calculation. Limit of detection and limit of quantitation must sit comfortably below the AET, calibration must be demonstrated across the relevant concentration range, and matrix effects must be characterised since the drug product matrix can suppress or enhance analyte response relative to a simple solvent standard. Where an authentic reference standard is unavailable for a detected compound, semi-quantitation against a structurally related standard, combined with transparent reporting of the assumptions involved, can be sufficient to support a toxicological risk assessment, an approach reflected in PQRI's threshold guidance. Choosing between LC and GC-based platforms, and understanding when each is the more appropriate first-pass tool, is covered in more detail in a comparison of HPLC and mass spectrometry approaches.
Materials and single-use systems: screening and supplier controls
Single-use manufacturing systems, including bags, tubing, filters and connectors, introduce their own extractables profile distinct from primary container closure materials, and the polymer classes involved recur across suppliers: polyethylene and polypropylene contribute antioxidants and slip agents, silicone tubing contributes siloxanes and platinum catalyst residues, and adhesive-bonded assemblies contribute acrylates and curing by-products.
- Antioxidant packages in polyolefins, commonly hindered phenols such as Irganox-type stabilisers, are among the most frequently reported extractables in single-use system studies.
- Siloxane oligomers from silicone tubing and gaskets appear consistently in extractables profiles for biologics manufacturing trains.
- Residual catalysts, including platinum from silicone curing, show up in ICP-MS-based elemental screens.
- Adhesive residues, particularly acrylate-based compounds, are relevant wherever bonded or laminated assemblies contact the product stream.
Evidence comparing processed components against unprocessed resin shows meaningful overlap in the compounds detected, but processing steps such as moulding, gamma irradiation or ethylene oxide sterilisation can introduce additional extractables not present in the raw resin, a finding consistent across polymer material evaluations. This means resin certificates from a supplier are a useful screening input for narrowing candidate materials, but they are not a substitute for testing the actual processed, sterilised component that will contact the drug product.
Supplier qualification programmes should require batch-specific certificates of analysis, documented extractables data for the specific processed component, and a formal change-management clause obligating the supplier to notify the sponsor of any formulation, resin source or processing change. A resin reformulation that a supplier considers minor can shift the extractables profile enough to require re-qualification, so the trigger for re-testing should be written into the supply agreement rather than left to informal notification.
A phase-appropriate, risk-based E&L programme
A phase-appropriate extractables and leachables programme scales testing depth to development stage, starting with broad material screening early and narrowing to targeted, quantitative leachables monitoring as a product approaches commercial submission, following the risk-based logic embedded in ICH Q3E and reflected in PQRI's threshold-based recommendations.
- Early screening: candidate materials undergo controlled extraction studies across a solvent panel, generating a qualitative profile used to eliminate materials with high-risk extractables such as Class 1 compounds before formulation is locked.
- Material qualification: shortlisted materials proceed to quantitative extractables testing on production-representative lots, with results compared against the developing AET to flag compounds needing early toxicological attention.
- Clinical batch testing: components used in clinical supply undergo leachables testing at early stability timepoints, confirming that the extractables-predicted profile matches what actually migrates into the drug product.
- Commercial qualification: the final container closure system and any single-use manufacturing components undergo full leachables studies across the proposed shelf life, generating the stability-linked data required for dossier submission.
- Lifecycle management: any post-approval change to formulation, container material, supplier or manufacturing process triggers a re-evaluation against the existing E&L data set to confirm the original safety case still holds.
Criteria for advancing a material from screening to qualification typically include the absence of Class 1 leachables at concentrations approaching the SCT, an extractables profile consistent across at least two production lots, and no unresolved analytical signals that cannot be identified or ruled out as background contamination. Materials failing these criteria are either reformulated, replaced with an alternative supplier, or carried forward with a documented risk justification where no practical alternative exists.
Lifecycle triggers deserve particular discipline, since a formulation change, a new excipient supplier, or even a change in terminal sterilisation method can alter the extractables and leachables profile enough to invalidate previous qualification work. A pharmaceutical company operating under a Clinical Trial Notification pathway should build this re-evaluation step into its change-control procedures from the outset, a responsibility discussed further in relation to sponsor obligations under Australian clinical trial exemptions.
Pro Tip: Keep the extractables data set for every qualified material on file even after a component passes qualification, since a future formulation change may only require re-running the AET comparison against existing data rather than a full new extraction study.
Practical laboratory considerations, validation and reporting
Defensible extractables and leachables data depend on quality control elements that are easy to overlook under time pressure but difficult to retrofit once a study is complete. Method blanks, confirming the extraction solvent and sample handling introduce no background interference, and spiked recovery samples, confirming the method reliably detects analytes at concentrations near the AET, belong in every study design from the outset.
- Method blanks run alongside every extraction batch to distinguish genuine extractables from solvent or container contamination.
- Spiked recovery samples at concentrations bracketing the AET confirm the method's sensitivity where it matters most.
- Authentic reference standards, or well-justified structural surrogates where standards are unavailable, support accurate quantitation.
- Chain of custody documentation for every sample, from material receipt through extraction to final analysis, supports audit readiness.
- Chromatograms and spectra retained as raw data allow a reviewer to independently verify reported identifications rather than relying on summary tables alone.
Regulatory-quality reporting packages a methods appendix describing extraction conditions, instrument parameters and validation data alongside representative chromatograms, mass spectra for any tentatively identified compound, and a clear quantitative summary linking each detected compound to its AET comparison and any toxicological qualification performed.
Poor correlation between an extractables profile and the leachables actually observed during stability testing is a common failure mode, and it usually traces to one of a few causes: extraction conditions too aggressive relative to real product exposure, a sample matrix in the leachables study that does not match the actual formulation, or secondary degradation reactions during storage that generate leachables absent from the original extractables profile. Addressing the mismatch typically means revisiting extraction stringency, confirming the leachables study used the true drug product matrix rather than a surrogate, and extending stability timepoints far enough to capture ageing-related compound formation.
Regulatory submission checklist and sponsor responsibilities
A dossier submission covering extractables and leachables should demonstrate, at minimum, that every product-contact material has been identified, tested under an appropriate controlled extraction protocol, and evaluated against AET and SCT thresholds with any qualified leachables carried through to a documented toxicological justification.
- Material identification: list every product-contact component, its polymer or elastomer composition, and its supplier, with certificates of analysis referenced.
- Extractables study reports: include full method descriptions, solvent panels, extraction conditions and quantitative results for each tested material.
- Leachables stability data: present results across the proposed shelf life, tied to the stability protocol timepoints and storage conditions.
- AET and SCT calculations: show the maximum daily dose basis, the applicable SCT, the uncertainty factor applied and the resulting AET used to flag reportable leachables.
- Toxicological justification: for any leachable above the AET, provide either a literature-based safety qualification or a dedicated toxicology study report.
- Pharmacopeial and guideline references: cite the relevant USP chapters and ICH Q3E explicitly where study designs follow those frameworks.
Organising these elements into a single, clearly indexed appendix, cross-referenced from both the quality and non-clinical modules of the dossier, reduces the reviewer's burden considerably compared to data scattered across multiple sections. For sponsors working through Australian submission requirements specifically, TGA reviewers expect this material identification and safety evidence to be traceable and complete, as set out in the agency's own guidance.
Publisher perspective on extractables and leachables risk assessment
Extractables and leachables risk assessment is, at its core, an exercise in reducing uncertainty about what a material will contribute to a drug product over its lifetime, and that uncertainty compounds when the underlying research materials themselves carry unknown provenance. Peptide researchers working through material qualification for injectable delivery systems face a version of this problem at the bench level: a leachable interacting unpredictably with a peptide active is a documented risk in prefilled syringe systems, and confidence in the peptide starting material itself removes one variable from an already complex assessment.
Laboratories building an E&L testing timeline around fixed stability timepoints benefit from a supply chain where sample receipt dates are predictable rather than a source of additional variability. Documented sterility testing protocols aligned to USP and WHO frameworks reflect the same underlying discipline that a rigorous E&L programme demands: traceable methods, retained raw data and results a reviewer can independently verify.
— Dr. Authur
Sourcing tested peptides and lab supplies for your E&L workflow
Researchers running extractables and leachables studies alongside peptide-based formulation work need materials whose identity and purity are not themselves a source of uncertainty in the safety case. Au Peptide Labs stocks pharmaceutical-grade research peptides across categories including Metabolic & GLP-1, Recovery & Repair, GH Secretagogues, Cognitive & Sleep and Longevity & Cellular research lines, alongside a dedicated Lab Supplies range covering consumables relevant to sample handling.
- Every batch ships with a certificate of analysis confirming high purity.
- Products are dispatched from a local facility promptly to support timely delivery.
- Express Post shipping options may be available to support faster domestic delivery.
- Packaging is designed to support laboratories managing sensitive material intake procedures.
Reliable, documented peptide supply removes one variable from a leachables risk assessment already carrying enough analytical complexity. Browse the full Au Peptide Labs range to source materials for your next study.
Sources
- Extractables and Leachables in Pharmaceutical Products: Potential Adverse Effects and Toxicological Risk Assessment
- Guideline for Extractables and Leachables (ICH Q3E) - Step 2 draft
- Australian regulatory guidance: impurities and related content in product dossiers (guidance excerpts)
FAQ
What is the difference between a leachable and an extractable?
An extractable is a compound released from a material under exaggerated laboratory extraction conditions, while a leachable is a compound that actually migrates into the drug product under normal storage and use. Leachables are generally a subset of extractables, though material ageing and secondary reactions can occasionally generate leachables not predicted by the original extractables profile.
How do you perform an extractables and leachables study?
An extractables study applies a panel of solvents, elevated temperatures and extended contact times to a candidate material to generate a broad chemical profile, calculated against the surface area to volume ratio of the component. A leachables study then tests the actual drug product across stability timepoints, comparing detected compounds against an AET calculated from the maximum daily dose and applicable SCT.
What are extractables in pharmaceutical materials?
Extractables are chemical entities such as antioxidants, plasticisers, residual monomers and processing aids that can be drawn out of packaging, container closure or manufacturing components under controlled, stringent laboratory conditions. They represent the full chemical space a material could potentially contribute to a drug product, not necessarily what it will contribute under real storage conditions.
What are leachables and why do they matter?
Leachables are the compounds from packaging or manufacturing materials that actually migrate into a drug product during its labelled shelf life, and they matter because they represent an unintended exposure pathway that can affect patient safety and product stability. Leachables classified as Class 1 under ICH Q3E carry specific compound limits and warrant avoidance wherever a formulation alternative exists.