When we consider environmental tests on products and materials, temperature and relative humidity immediately come to mind, which are the two factors that influence our surroundings more than any other.
But there is another factor that we tend to forget, as it is omnipresent: sunlight.
Exposure to sunlight can significantly affect especially certain types of products for which it is necessary to perform photostability testing
In today's article we will see which and how photostability testing works.
What is Photostability Testing for?
If you take the package of any medicine you have at home and look at the back, you will find a series of instructions on its storage. In addition to the classic "Keep in a cool, dry place", "Keep in the original packaging to protect from sunlight" is often used.
More than any other product, drugs - whether real medicines or cosmetic products - are extremely sensitive to exposure to sunlight.
In fact, the delicate chemical balance that guarantees their effectiveness can be affected not only by excessive temperature and high levels of humidity but also by sunlight as such.
This is why the photostability test is synonymous with the pharmaceutical sector and one of the main tests that all drugs must pass.
What is Tested in Photostability Testing
The indication you find on the packaging recommends, as is appropriate, maximum caution but in photostability testing all possible cases of exposure to sunlight are tested, i.e.:
- Packaging Test (Marketing Package)
- Blister Test (Immediate Packaging)
- Test on the exposed drug
- Tests on drug substances
Each phase is essential to verify the photostability of the drug in all storage conditions.
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How Photostability Testing is done
To carry out the photostability test it is necessary to have a suitable laboratory instrument: the stability chamber.
A stability chamber is a climatic chamber which, in addition to modifying and controlling the temperature and relative humidity parameters, is able to simulate exposure to sunlight at different intensities.
To do this, a set of specific UV lamps, also known as ICH lamps, are used.
They are named so because of the ICH, The International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use, the main international body that regulates these and other tests.
Photostability Testing according to ICH-Q1B
Per essere più precisi, lo standard che regola il test di fotostabilità nel settore farmaceutico è lo ICH-Q1B.
Within the standard, the international guidelines for carrying out the photostability test are set
When it comes to lighting, the ICH-Q1B offers two options:
- Any light source designed to produce an output similar to the D65/ID65 emission standard, such as an artificial daylight fluorescent lamp combining visible and ultraviolet (UV) outputs, xenon lamp, or metal halogen lamp. D65 is the internationally recognized standard for outdoor daylight as defined in ISO 18909:2022. ID65 is the equivalent standard for indoor indirect daylight. For a light source emitting significant radiation below 320 nm, one or more suitable filters can be fitted to eliminate such radiation.
- The sample should be exposed to both a cool white fluorescent lamp and an ultraviolet lamp. The cool white fluorescent lamp is designed to produce an output similar to that specified in ISO 18909:2022. The near-UV fluorescent lamp should have a spectral distribution from 320 nm to 400 nm with a maximum energy output between 350 nm and 370 nm; a significant percentage of UV should be in both the 320 to 360 nm and 360 to 400 nm bands.
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The FDM Lighting Chamber for Photostability Testing
The FDM Illumination Chamber is the ideal tool to perform the photostability test in accordance with the ICH-Q1B standard.
Our light chambers come with multiple lighting sets to simulate sunlight under different conditions.
Alternatively, you can purchase a normal climate chamber with a separate set of UV lamps.
For further doubts and questions, please do not hesitate to contact us.
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