USP Class VI Certification

USP Class VI certification is a designation that a specific plastic material or component has passed the most stringent tier of biological reactivity testing under United States Pharmacopeia (USP) General Chapter <88>, “Biological Reactivity Tests, In Vivo.” Chapter <88> sorts plastics into six classes (I through VI) according to which combination of three in-vivo bioassays — systemic (acute) toxicity injection, intracutaneous reactivity, and implantation — a material passes, and at what extraction rigor. A material reaches Class VI, the highest tier, only when it passes all three assays using extracts prepared at the most demanding temperature and duration condition the material can withstand without degrading. For procurement and QA staff sourcing lab plasticware, single-use bioprocessing components, or pharma-adjacent consumables, USP Class VI certification is the specific, checkable claim to verify — not a general assurance of “medical-grade” or “biocompatible” plastic.

The Six USP Plastic Classes

USP <88> defines Classes I–VI as a cumulative ladder, not six unrelated categories. Class I requires only the systemic injection test. Each higher class adds either another bioassay or a more rigorous extraction condition (higher temperature, longer duration, or an added extraction vehicle), until Class VI, which requires the material to pass all three bioassays — systemic injection, intracutaneous reactivity, and implantation — using extracts prepared under the harshest condition applicable to that material. A Class VI result therefore implies the material would also satisfy every lower class; the reverse is not true. This is why Class VI is treated in procurement and regulatory-affairs practice as the baseline expectation for plastics that will contact drug product, biologic material, or tissue for any meaningful duration.

What the Three Class VI Bioassays Test

• Systemic injection test — an extract of the material, prepared in one or more standard vehicles (such as physiological saline, cottonseed oil, or a polyethylene glycol/alcohol-saline mixture), is injected into mice, which are then observed for signs of acute systemic toxicity.
• Intracutaneous (intradermal) reactivity test — the same extracts are injected into the skin of rabbits, and injection sites are scored for erythema and edema against a vehicle control.
• Implantation test — strips of the material itself are surgically implanted into rabbit tissue and, after an observation period, the surrounding tissue is examined histologically for signs of adverse local reaction compared with a negative-control implant.

All three are in-vivo animal assays run by an accredited toxicology testing laboratory against the specific extraction protocol Chapter <88> specifies for the material’s autoclave/heat stability — not bench-level physicochemical tests and not the same battery of tests used under ISO 10993.

USP Class VI vs. ISO 10993 Biocompatibility

USP Class VI and ISO 10993 are related but not interchangeable, and treating them as synonyms is a common procurement mistake. USP <88> is a materials-level pharmacopeial test battery, historically built around drug-contact packaging and components; ISO 10993 is a broader, risk-based biocompatibility evaluation framework, built around a finished medical device and its actual clinical contact type and duration, that FDA expects device manufacturers to work through under 21 CFR 820 design controls. A resin can be USP Class VI certified and still require additional ISO 10993 endpoint testing (cytotoxicity, sensitization, genotoxicity, and others depending on device classification) once it is incorporated into a finished device. Class VI certification on a raw material or component is a strong, useful signal — often a supplier-selection prerequisite — but it does not by itself satisfy a finished device’s ISO 10993 biocompatibility file. See CASRAI’s guide to FDA biocompatibility guidance and ISO 10993 for how the device-level framework works.

What to Verify Before Accepting a Class VI Claim

Because USP Class VI certification attaches to a specific material formulation, tested as extracted at a specific condition, a handful of checks separate a real, checkable certification from an unsubstantiated marketing claim:

• Ask for the certificate of analysis (COA) or test report, not just a data sheet that states “USP Class VI compliant” with no underlying reference. The report should identify the accredited testing lab, the test dates, and the specific resin grade/lot tested.
• Confirm the certification matches the exact product being purchased — the same base polymer under a different additive package, colorant, regrind (recycled-content) ratio, or molding process is a different material for Chapter <88> purposes and may not carry the same certification.
• Check whether post-manufacture processing is covered. A resin can be Class VI certified in its raw state while a downstream step — gamma or e-beam sterilization, for instance — changes its extractable profile enough to warrant re-testing; some suppliers certify the finished, sterilized component specifically for this reason.
• Don’t treat Class VI as a substitute for a device-level biocompatibility file if the component becomes part of a regulated finished device — confirm with regulatory affairs whether ISO 10993 testing is still required at the device level.

Materials Commonly Certified to USP Class VI

Plastics routinely offered with USP Class VI certification in lab and pharma-adjacent supply chains include polypropylene and polycarbonate (common in centrifuge tubes, pipette tips, and rigid labware), certain polyethylene grades, platinum-cured silicone (common in single-use tubing and bioprocessing bags), and PTFE and related fluoropolymers. Certification is always specific to the named grade and manufacturer — “polypropylene” as a polymer family is not itself Class VI certified; a particular resin grade from a particular supplier, tested under Chapter <88>, is.

Frequently Asked Questions

Is USP Class VI plastic the same as medical-grade plastic?
No. “Medical-grade” has no single regulatory definition and is sometimes used loosely in marketing. USP Class VI is a specific, testable pharmacopeial classification with a defined test battery behind it — always ask for the certification and test report rather than accepting the label “medical-grade” alone.

Does USP Class VI certification expire or need to be repeated?
Chapter <88> itself doesn’t impose a fixed expiration date, but a certification is tied to a specific material formulation and manufacturing process; suppliers typically re-test if the resin formulation, additive package, or process changes, and buyers should confirm the certificate on file still matches the current product before relying on it.

Who performs USP Class VI testing?
Accredited toxicology and biocompatibility testing laboratories run the Chapter <88> bioassays on behalf of material and component manufacturers; the manufacturer then makes the resulting certification and test report available to purchasers, typically on request or via a certificate of analysis.