What is PET?
PET stands for Polyethylene Terephthalate. It's a type of polyester resin, commonly used to make plastic bottles and containers, especially for liquids. PET is known for being strong, durable, and recyclable.
What Does USP Class VI Mean?
The U.S. Pharmacopeial Convention (USP) is an independent, non-profit body tasked with defining quality benchmarks for medicines, dietary supplements, food ingredients and healthcare materials. Among its many standards, USP publishes a set of biocompatibility protocols (General Chapter <88> of the USP–NF) that apply to plastics destined for contact with human tissue in medical or surgical devices.
USP Class VI is the strictest of six in vivo designations under USP <88>. To earn this label, a polymer must clear three biological-reactivity challenges—systemic injection, intracutaneous exposure and implantation—using a variety of extraction media to simulate different physiological environments.
USP <88> Bioreactivity Tests (In Vivo)
| Test Type | Extract Medium | Applies to USP Class |
|---|---|---|
| 1. Systemic Injection (Model 1) | 0.9% Sodium chloride (IV) | I, II, III, IV, V, VI |
| Alcohol-saline (IV) | I, II, III, IV, V | |
| Polyethylene glycol (IP) | I, II, III | |
| Vegetable oil (IP) | I, II, III, IV | |
| 2. Intracutaneous Implant (Model 2) | 0.9% Sodium chloride (IV) | I, II, III, IV, V, VI |
| Alcohol-saline (IV) | I, II, III, IV, V | |
| Polyethylene glycol (IP) | I, II | |
| Vegetable oil (IP) | I, II, III | |
| 3. Implantation (Model 2) | No extract (direct implant) | V, VI |
(IV = intravenous; IP = intraperitoneal)
What the Three USP Class VI Tests Involve
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Acute Systemic Toxicity: The material (or its extract) is administered to test animals to screen for any toxic or irritant effects after injection.
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Intracutaneous Reactivity: Extracts are injected into the skin to check for localized irritation or sensitization.
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Implantation Study: Samples are implanted into muscle tissue for several days to observe any inflammatory or toxic response.
Passing all three ensures a polymer has extremely low in vivo reactivity. In addition, materials are typically subjected to defined temperature-conditioning protocols, further demonstrating stability and safety under various processing and sterilization conditions
