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Medical Device Stability Testing Standards

Medical device stability testing refers to the ability of a devices to maintain its physical, chemical, and functional properties over time when stored under specified conditions. The goal of stability testing is to ensure that the device remains safe and effective throughout its intended shelf life.

Medical device stability testing is an important aspect of the regulatory process to verify the safety and efficacy of these devices throughout their lifecycle. These testing are conducted to assess how a medical device performs under various environmental conditions over time. A stability studies is essential to determining the medical device’s shelf life, storage recommendations, safety, and efficacy throughout its intended use.

Purpose: The purpose of the medical device stability testing is to give information on how the quality of medical devices does not vary with time under the influence of a variety of environmental factors such as temperature and humidity.

Medical Device Shelf Life: The ability of a stability studies is to maintain its performance characteristics within the limits specified by the manufacturer for medical devices. The shelf life is the duration during which the device is expected to retain its functional and structural integrity and meet its intended performance specifications when stored under recommended conditions.

Medical device stability testing are done to determine how the environment affects the product’s strength, quality, and purity. This includes temperature, light, moisture, pH, agitation, and gravity.

There are internationally accepted standards for assessing the stability of medical devices in general and also certain product-specific standards based on the product type. Applicable standards have to be identified before initiating the testing.

The medical devices stability can be demonstrated in two ways:

1. Accelerated stability of medical devices: In accelerated stability testing, a product is kept at elevated stress conditions (such as temperature, humidity, and pH) for a shorter period of time.

2. Real-time stability of medical devices: In real-time stability testing, a product is kept at recommended storage conditions and tested at periodic intervals until it fails the specification.

Medical Device Stability Testing Applicability

According to the IMDRF- Essential Principles of safety and performance of medical devices and IVD Medical Devices, Stability applies to:

Sterile and non-sterile medical devices over a given time period whose physical/chemical/functional properties can be altered or compromised.
IVD reagents, calibrators, and controls, when stored, transported, and used in the conditions stated by the manufacturer,
Lyophilized materials restored to the original state, working solutions and materials removed from sealed containers, when prepared, used, and stored according to the manufacturer’s IFU,
Measuring instruments or systems after calibration.

The guideline for stability testing for pharmaceutical products are ICH guideline Q series and there is an FDA guidance for shelf life of medical devices.

In the EU MDR, it is stated that the stability test including shelf-life is to be compulsorily established for all medical devices under product verification and validation and it should be part of the technical file and documentation.

Determining the Medical Device Stability Testing

While determining the stability of medical devices following are also considered:

Storage conditions, e.g., temperature variations, relative humidity, ventilation, air pressure, air-borne contamination, visible light, and other radiation, etc.
The type of the device and intended use.
The components or materials used for the manufacturing of the device.
Method of manufacture
Packaging, e.g. Products that are packaged in different sizes of packages may each have different stability or shelf life due to the difference in packaging area coming in contact with the product.
Transportation conditions, e.g., vibration, shock, temperature, humidity, pH, etc.

Medical Device Stability Evaluation Criteria

The following criteria are used to evaluate the stability of medical devices:

Chemical – Degradation, Interaction, Device packaging and interaction, Radioactive decay, Manufacturing
Physical – Physical characteristics, Manufacturing process, Storage conditions
Microbiological – Sterility, Environmental control, antimicrobial effectiveness
Therapeutic, and
Toxicological
Biocompatibility Testing

Verifying the stability/shelf life

The following criteria are used to evaluate the stability of medical devices:

Storage Plan for medical device
Sampling plan – that defines the frequency of sampling and test to be performed at each interval.
Testing during various phases of the stability study
Evaluating the packaging of the medical device
Simulation of shipping and handling stress

On-going Medical devices stability testing

The product can be released in the market based on the data of accelerated stability testing of medical devices; however, real-time medical devices stability test shall be carried out simultaneously.

After a marketing authorization has been granted, the stability testing of medical devices should be appropriately monitored according to a continuous Program that will permit the detection of any stability issue (e.g., changes in levels of degradation products)

Stability Testing Criteria and Variables

The United States Pharmacopoeia (USP) defines stability as “the extent to which a product retains, within specified limits, and throughout its period of storage and use, i.e., its shelf life, the same properties and characteristics that it possessed at the time of manufacture.” There is no one exhaustive set of criteria that would apply equally to all medical devices.

Although this set of criteria applies specifically to the evaluation of drug product stability, it is useful as a starting point in developing a set of criteria to evaluate the stability of medical devices.

The following outline may be useful in identifying parameters that could significantly affect the shelf life of a device, even though all of the criteria will not apply to every device. This outline is based on the criteria listed above with the addition of biocompatibility.

1. Chemical

1.1 Degradation: Do any active ingredients or components of the device degrade over time in a manner that adversely affects device safety or performance?

1.2 Interactions: Do ingredients or components interact to alter the device? Does the device have interactions among the various components that cause degradation of the ability to perform the intended function?

1.3 Device and Packaging Interaction: Is there an interaction between the device and package that has undesirable effects?

1.4 Radioactive Decay: Does the device contain radioactive material with a relatively short half-life? Do the radioactive decay by-products alter the safety or effectiveness of the device either by themselves or through further interaction?

1.5 Manufacturing: Do any of the manufacturing processes alter the chemistry of the raw materials, components, or finished device in a manner that adversely affects device Safety or performance?

2. Physical

2.1 Physical Characteristics: Does the device have physical characteristics that vary with time, e.g., appearance, viscosity, elasticity, tensile strength, burst strength, or electrical resistance?

2.2 Manufacturing Process: Do the different steps in the manufacture of the device affect the physical characteristics of the individual components or the finished device in a manner that adversely affects device safety or performance?

2.3 Storage Conditions: Do the storage conditions, e.g., temperature, humidity, light, etc., have an effect on the device in a manner that adversely affects device safety or performance?

3. Microbiological

3.1 Sterility: Do sterile devices remain sterile? Maintenance of sterility is primarily determined by the maintenance of package and seal integrity.

3.2 Environmental Control: Is an environmental control program needed during manufacturing or storage to monitor and adjust the microbial load in or on the device and packaging below an established tolerance level to prevent adverse degradation of the product?

3.3 Antimicrobial Effectiveness: Does the device lose the ability to perform the intended antimicrobial function?

3.4 Integrity: Do the device’s barrier characteristics change?

3.5 Preservative Effectiveness: If the device uses a preservative system, how long does the preservative system retain effectiveness within tolerance levels?

4. Therapeutic: Does the ability of the device to perform the intended therapeutic or diagnostic function change under storage or use conditions?

5. Toxicological: Do device degradation by-products form during storage or use that produce an adverse toxic effect?

6. Biocompatibility: Does the biocompatibility of the product change adversely during storage or use?

There are numerous variables that affect the shelf life of a medical device. Some of these were discussed in the stability criteria outlined above while additional product-dependent variables are listed below. Although manufacturers may not be able to control all of the variables, their effect on device performance can be minimized if properly considered.

Storage conditions, e.g., temperature variations, relative humidity, ventilation, a n pressure, air-borne contamination, visible light and other radiation, etc.
The nature of the device and intended use, e.g., medical gloves are made of latex because of the intended use even though latex deteriorates with age.
The components used to manufacture the device, e.g., some devices contain a battery or other components that would suffer degradation of function with the passage of time.
Method of manufacture, e.g., an in vitro diagnostic device that is aseptically packaged may have a shorter shelf life than one that is terminally sterilized.
Packaging, e.g., products that are packaged in different size containers may each have a different stability shelf life due to the different ratio of product to package surface area contact.
Transportation conditions, e.g., vibration, shock, temperature, humidity, etc.

Medical Device Stability Storage

Due to the integration of active pharmaceutical ingredients (API) and antimicrobial agents, more medical devices are being considered combination products than ever before. While the stability of these ingredients is often known, it must be tested in conjunction with the device and undergo a complete stability study according to the ICH guidelines.

Stability conditions available for Medical Devices storage:

25°C ± 2°C / 60% RH ± 5% RH

30°C ± 2°C / 65% RH ± 5% RH

40°C ± 2°C / 75% RH ± 5% RH

5°C ± 3°C

–20°C ± 5°C

Biological Storage:

Biological Storage includes refrigerated and freezers and can offer customized storage as required.