ISO 10993-1:2025 Revision Highlights Part 2

Exposure Duration = Exposure + Duration

Calculation of Exposure Duration for Categorization of Medical Devices

While exposure duration is not a new concept in ISO 10993-1, the 2025 revision provides specific guidance on the categorization of devices and how to calculate the exposure duration based on device contact. The revised exposure duration structure is primarily due to considerations for the cumulative exposure of chemical constituents (alignment with ISO 10993-17 and -18), accounting for repeated use of medical devices rather than relying only on broad duration based device categorization. This update also improves biological evaluation by aligning testing requirements with exposure and actual clinical use.

New key concepts for considering exposure duration are:

Daily contact

Daily contact means a medical device touches the body each day, even if only briefly. Total exposure period refers to the number of calendar days from first to last use, or until the device is replaced for the same patient.

Intermittent contact

If there is an interval of at least 24 hours between consecutive periods of tissue contact with the device, this is classified as intermittent contact. This can be repeated use of one medical device or a replacement of the medical device under consideration.

Bioaccumulation

Bioaccumulation of medical device constituents should be evaluated across all duration categories. If bioaccumulation in humans is anticipated based on the contact duration of the medical device, it must be considered in the risk assessment.

Categorization based on Duration

The categorization of the devices based on the duration of use is still applicable and is the same as in the current version. Devices are categorized based on the anticipated duration of direct or indirect contact. If multiple exposures occur to the patient with the same device, the duration category should be based on the total exposure period for a single patient. If a medical device can be placed in more than one duration category, the biological evaluation should be based on the longest contact duration or the worst-case category. If the medical device can be placed in more than one body category, the biological evaluation should be based on the most invasive contact. If the device could be placed in multiple categories, then the biological evaluation should be based on the worst-case scenario.

Limited exposure:  a medical device that has a total exposure period of ≤ 24 h.

Prolonged exposure: a medical device that has a total exposure period of > 24 h ≤ 30 days.

Long-term exposure: a medical device that has a total exposure period of > 30 days.

Categorization based on Body Contact

The fundamental principle for categorizing medical devices according to body contact remains consistent with the current edition of the ISO 10993-1 standard. However, some changes have been introduced with body contact categorization. Specifically, terminology such as surface device, externally communicating, or implant were replaced with more relevant definitions focused on the specific tissue contact.

Devices are now categorized based on the tissue (body) contact as:

1. Non-contacting medical devices:
   Devices that do not come into direct or indirect contact with the patient’s body during clinical use. Examples: Diagnostic software, point of care testing devices that analyze samples removed from the body.
2. Devices in contact with intact skin:
   Devices that are designed to touch but not penetrate or compromise intact skin either directly or indirectly. Examples: tapes, bandages.
3. Devices in contact with intact mucosal membrane:
   Devices that are intended to interact directly or indirectly with mucosal membranes (digestive system, respiratory system, reproductive tracts) that are intact and healthy. Examples: stomach tubes, colonoscopes.
4. Devices in contact with breached or compromised surfaces (skin or mucosal) or internal tissues other than circulating blood:
   
   1. Surface contacting devices – direct or indirect contact
      Devices that are used in areas where the skin or mucosal membrane is no longer intact or that come into contact with internal tissues, excluding direct interaction with circulating blood. Examples: Wound healing, dressings.
   2. Bone, dentin, internal soft tissues or organs contacting devices – direct or indirect contact
      Devices that come into contact with internal tissues, excluding direct interaction with circulating blood. Examples: endoclips, pacemaker.
5.  Devices in contact with circulating blood:
   Devices that have direct exposure to the patient’s bloodstreams, including devices that store blood, act as conduits to deliver fluids or blood. This category does not include devices that come in contact with bleeding tissue, which may be categorized having contact with tissues. Examples: blood-transfusion devices,  vascular grafts.

The revisions made to ISO 10993-1 are expected to bring more clarity and consistency to device categorization. By emphasizing cumulative exposure, repeated use, and bioaccumulation, the updated standard brings more refinement to biological risk assessments and patient safety. As manufacturers and regulatory professionals adapt to these changes, they will be equipped to conduct thorough, relevant biological risk evaluations that reflect actual clinical use.

MED Capabilities

MED Institute provides comprehensive biological risk assessment services to support the safety evaluation of medical devices in accordance with ISO 10993 and related regulatory requirements. Our multidisciplinary team of professionals offers expert guidance on material characterization, biological equivalence assessment, toxicological evaluation of chemical constituents, and even support in responding to submission deficiencies. MED Institute technical experts have extensive experience in developing biological evaluation plans and biological evaluation reports in compliance with global regulatory standards and based on sound scientific principles. By engaging with our team of experts, several manufacturers have designed safer products and accelerated their regulatory submissions and successful market entry.

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