The U.S. Pharmacopeial Convention (USP) is a non-profit organization, with a purpose of creating standards for medications, food ingredients, dietary supplements and healthcare technologies. The USP publishes bio compatibility protocols for the plastics and polymers used in medical devices or surgical equipment, that may come in contact with human tissue.
USP Class VI refers to one of the six designations for plastics from General Chapter <88> of the United States Pharmacopeia and National Formulary (USP-NF). This chapter provides guidelines for testing and certification of a material to be used within a medical device.
USP Classification of Plastics (USP <88> Biological Reactivity Tests, In Vivo)
|
Test |
Extracts |
USP Class |
|||||
|
I |
II |
III |
IV |
V |
VI |
||
| Systemic injection test – injection in test model 1 | Sodium chloride (intravenous) |
X |
X |
X |
X |
X |
X |
| Alcohol saline (intravenous) |
|
X |
X |
X |
X |
X |
|
| Polyethylene glycol (intraperitoneal) |
|
|
X |
|
X |
X |
|
| Vegetable oil (intraperitoneal) |
|
|
X |
X |
X |
X |
|
| Intracutaneous test – injection in test model 2 | Sodium chloride (intravenous) |
X |
X |
X |
X |
X |
X |
| Alcohol saline (intravenous) |
|
X |
X |
X |
X |
X |
|
| Polyethylene glycol (intraperitoneal) |
|
|
|
|
X |
X |
|
| Vegetable oil (intraperitoneal) |
|
|
|
X |
X |
X |
|
| Implantation test – strips implanted in test model 2 | None |
|
|
|
X |
|
X |
The USP Class VI designation is considered the most stringent and, therefore, most useful for medical applications. It involves the following three in vivo biological reactivity evaluations, generally performed on mice or rabbits to mimic use in humans:
- Acute Systemic Toxicity (Systemic Injection) Test: Measures toxicity and irritation when a sample of the compound is administered orally, applied to the skin, and inhaled.
- Intracutaneous Test: Measures toxicity and localized irritation when the sample is in contact with live subdermal tissue (specifically, the tissue that the medical device is intended to contact).
- Implantation Test: Measures toxicity, infection, and irritation of an intramuscular implantation of the compound into a test animal over several days.
In addition to demonstrating an extremely low level of toxicity by passing these three tests, the material will be subjected to several temperature assessments for set periods of time. Materials that meet USP Class VI standards generally ensure a high quality level and better acceptance with the FDA and USDA because the materials are believed to substantially reduce the risk of causing harm to patients from reaction to a toxic material.
USP Class VI Testing is only one standard of biocompatibility, however. Though not a limited series of tests, some biocompatibility requirements for medical devices may exceed the testing performed in USP Class VI. A more rigorous standard for the biological evaluation of medical devices is ISO-10993.
ISO-10993 is a standard that utilizes systemic toxicity and intracutaneous reactivity testing. However, it also includes additional cytotoxicity, genotoxicity, chronic toxicity, and hemocompatibility tests, as well as more involved systemic toxicity testing. The additional intensity of ISO-10993 testing is due to it primarily being required for medical devices that will be permanently or semi-permanently implanted into a patient. Therefore, for devices that are not intended to be implanted or will have limited contact with patients, ISO-10993 testing may be more extensive than necessary.
For more information, please visit www.namsa.com.
For USP Class VI information pertaining to a specific Foster compound, please refer to Biocompatibility Certifications.