USP Class VI Testing

June 7, 2016 – by Eastern Seals

What is USP Class VI Testing?

USP (United States Pharmacopeia) is an independent public health organisation that promotes public health, establishing state-of-the-art standards for quality, purity, strength and consistency. These USP Standards are published in the US Pharmacopeia and the National Formulary (USP NF).

USP Class VI compliance is often requested by end users such as medical device and pharmaceutical processing companies as it provides added assurance for the quality and performance of utilised materials.

Eastern Seals (UK) Ltd can provide a variety of USP Class VI compliant O-rings, sanitary gaskets and seals in various elastomer types, including EPDM, SILICONE, FKM (VITON), and PTFE (TEFLON).

USP Class VI compounds must be made from ingredients with clear histories of biocompatibility that meet tight requirements for leachates.

USP Class VI Plastic Tests are designed to evaluate the biological reactivity of various types of plastics materials in vivo. Developed to test drug containers, the class plastics tests are frequently carried out on unmolded plastic resins as well as containers. Class plastics testing is not a replacement for biocompatibility testing, but is commonly used by manufacturers to classify materials.

There are three in vivo tests included in the classification of plastics. The Systemic Injection Test and the Intracutaneous Test are designed to control the systemic and local biological responses to plastics and other polymers by the single-dose injection of specific extracts made from a sample. The third test, the Implantation Test, is designed to assess the reaction of living tissue to a test material.


This test measures the irritant effect of the test material and governs its human hazard potential. Toxicity is determined by oral, dermal and inhalation.


This specific test administers the material straight to the tissues it will be in contact during normal use without protection of the skin or any other body system. This will allow the testing team to assess the response of particular tissues to the material.


The implantation test determines the response of live tissue to the material when implanted into a live animal. The standard implantation time required for a USP Class VI test is five days. If after the five-day period there are no signs of irritation or toxicity, it will meet the implantation requirements of the test.


The material extracts used on the systemic toxicity and intracutaneous tests are fixed at set temperatures and exposure times to ensure the results meet a common standard. All material extracts are processed using three different temperature and time exposure conditions. Initially it is administered at 50°C (122°F), for 72 hours, then at 70°C (158°F) for 24 hours and finally at 121°C (250°F) for one hour.

For a product to pass USP Class VI standards, it must exhibit a very low level of toxicity by passing all of the tests requirements. Testing for compliance involves an assessment of the effects of the material, and extractables on tissue.

The USP defines six plastics classes, from I to VI (VI remaining the strictest). Consequently, we find it beneficial to ensure some of our materials are certified as USP Class VI, particularly if the seal is to be used in medical devices. A plastic resin material that has passed Class VI certification is expected to be more likely to produce favourable biocompatibility results.

Who uses USP Class VI elastomers?

Primarily biopharmaceutical manufacturers for their process equipment
Sanitary pumps require Class VI O-rings and seal material.
Sanitary diaphragm valves have USP Class VI diaphragms.
Most single use process components such as silicone and tubing, plastic connectors and single use bags all require USP Class VI certification
Sanitary Tri-Clamp gaskets are all required to be USP Class VI

For more information on UPS Class VI seals, or to place your order, contact Eastern Seals by phone, +44 (0) 1670 840529 or email

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Eastern Seals (UK) Ltd
Unit 3 Sovereign Business Park
Jubilee Industrial Estate
Ashington | Northumberland
NE63 8UG

+44 (0) 1670 840529
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