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Regulatory Focus™ > News Articles > 2020 > 10 > FDA releases guidance documents on biocompatibility submissions and nitinol-containing devices

FDA releases guidance documents on biocompatibility submissions and nitinol-containing devices

Posted 15 October 2020 | By Mary Ellen Schneider 

FDA releases guidance documents on biocompatibility submissions and nitinol-containing devices

The US Food and Drug Administration (FDA) has issued two new guidance documents related to premarket submissions on device biocompatibility with intact skin, as well as technical considerations for nitinol-containing devices.
In the draft guidance, issued 15 October, the FDA provided select updates on the type of compatibility information that should be included in premarket submissions for devices made from common polymers and fabrics that come in contact with intact skin. The draft guidance outlines the criteria for certain devices made from materials with “very low biocompatibility risk” and a “long history of safe use in medical devices” to bypass biocompatibility testing.
“This select update describes a least burdensome approach for these devices that recommends specific material information in a premarket submission in lieu of biocompatibility testing,” the FDA wrote.
The agency has existing guidance on devices that have contact with the human body, which will remain in effect until the draft document is finalized.
The draft guidance applies to medical devices that contact intact skin surfaces only; have limited (24 hours or less), prolonged (24 hours to 30 days), and long-term (more than 30 days) contact durations, including repeat uses; and are composed of certain types of materials.
The materials include several synthetic polymers and a small number of fabrics.
The synthetic polymers include:
  • Acrylonitrile butadiene styrene (ABS)
  • Cured epoxy adhesives
  • Fluoropolymers including polytetrafluoroethylene (PTFE), expanded polytetrafluoroethylene (ePTFE), polyvinylidene fluoride (PVDF), and fluorinated ethylene propylene (FEP)
  • High impact polystyrene (HIPS)
  • Polyamides, including nylon
  • Polybutylene terephthalate (PBT)
  • Polycarbonate (PC)
  • Polyetheretherketone (PEEK)
  • Polyether imide (PEI)
  • Polyethylenes, including low-density polyethylene (LDPE) and high-density polyethylene (HDPE)
  • Polyethylene terephthalate (PET)
  • Polymethylmethacrylate (PMMA)
  • Polyoxymethylene (POM)
  • Polyphenolsulfone (PPSU)
  • Polypropylene (PP)
  • Polyurethane (PU)
  • Silicone
The fabrics include:
  • Polyurethane fabrics, including Lycra
  • Cotton fabrics
  • Polyamide fabrics, including nylon
  • Silk fabrics
The FDA also spelled out some exclusions to this policy, such as devices that have components that have contact with intact skin and are fabricated from materials not specifically listed in the guidance, such as titanium, stainless steel, nitinol, or gold. These fabrics are excluded either because of their known risks or inadequate experience with the materials. “Biocompatibility testing or detailed rationales for omission of this testing could address these concerns,” the FDA wrote.
The agency is asking device sponsors to include a list of all materials used to fabricate the device that has direct or indirect skin contact, a statement confirming that the listed materials have a documented history of safe use in legally-marketed medical devices in the U.S. that have contact with intact skin, and a statement confirming that none of the listed exclusions apply.
The agency also advised sponsors to describe any redness, swelling, irritation, sensitization, allergy, immune response, or other reasons observed in clinical studies and attributed to the device.
Sponsors should also document how they have determined the biocompatibility risks for the devices are addressed so that biocompatibility testing is not necessary, such as through purchasing controls of device materials, production and process controls for manufacturing materials, or medical device reporting.
The draft guidance also suggests labeling on possible adverse skin reactions when the device is intended for use in patients who may not be able to identify adverse biological reactions, such as patients with epilepsy or dementia.
Nitinol-containing devices
The FDA also issued final guidance on technical considerations for the non-clinical assessment of nitinol-containing medical devices. The guidance updates a draft document, issued in 2019. (RELATED: CDRH Draft guidance tackles Nitinol Devices, Regulatory Focus, 18 April 2019).
“With an increasing trend to treat patients using minimally invasive procedures, nitinol has become a popular choice of material due to its ability to return to its original shape after being mechanically deformed or after heat is applied,” the FDA wrote. “Given the complex thermomechanical behavior of nitinol, there are unique considerations when assessing the safety and performance of nitinol devices.”
The final guidance applies to medical devices that have at least one nitinol component that has patient contact. The technical areas covered by the guidance include mechanical testing, corrosion, biocompatibility, and labeling.
For nitinol-containing devices with prolonged exposure and permanent contacting devices, the agency is recommending that sponsors provide information on material composition, manufacturing, pseudoelasticity or shape memory behavior, and transformation temperatures. Devices with limited exposure may not need to provide as much information, depending on the device design and intended use.
The FDA recommended pitting corrosion testing for nitinol devices with prolonged exposure and permanent contacting devices, due to the potential for nickel ion release and possible compromise of the mechanical integrity of the device.
The guidance also specifically recommends labeling to warn patients about the risk of a potential allergic reaction to nickel. “Since there is no known lower limit on the amount of nickel that can elicit allergic reactions in some patients, we recommend that the risk of potential allergic reaction to nickel be mitigated through labeling for nitinol containing devices,” the agency wrote.

Biocompatibility guidance
Nitinol guidance

Tags: devices, FDA, medical, US

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