Light Stability Analysis

Light stability testing in the pharmaceutical industry is necessary to ensure the potency, efficacy and safety of manufactured products in clinical use. Photostability testing of APIs and products is performed according to ICH Q1B guidelines, and the selection of an appropriate light source is an important consideration for consistent results. Photodegradation of drugs in products is a function of spectral distribution and light source intensity. Therefore, a specific light source needs to be selected for the photostability assessment.

Light Stability Analysis


The photostability of a drug substance can be defined as the response of a drug or formulation to exposure to sunlight, ultraviolet light and visible light in a solid, semi-solid or liquid state, resulting in physical or chemical changes. The response of a drug to light absorption and excitation can be considered through photodegradation reactions by free radical formation or photosensitization reactions by intermolecular energy transfer. Many drugs with different molecular structures are photoreactive. They undergo degradation reactions in water and organic solvents through various pathways upon exposure to light. The main modes of drug photodegradation are as follows: photo addition, photo hydration, photo cyclization, photo dealkylation, photo dehalogenation, photo dehydrogenation, photo dimerization, photo elimination, photo induced hydrolysis, photo isomerization, photo oxidation, photo induced rearrangement, photo reduction, photo induced ring cleavage, etc.

Our Services

CD Formulation can provide clients with photostability analysis of drugs, assess the overall photosensitivity of the drug for development and validation purposes, and provide information needed for handling, packaging, and labeling. Determine the intrinsic photostability characteristics of new APIs and products during the development process. Given the photosensitivity and photostability of a drug, we can evaluate the following.

Inherent photostability characteristics

  • Physical and chemical changes that occur with exposure to light
  • Efficacy of stabilizers in light stabilization
  • Light effects during packaging, transport and storage
  • Light-induced biological effects

Light stability test content

  • Forced degradation test

Test samples include APIs or solutions/suspensions of APIs for analytical method validation. Forced degradation studies may use different exposure conditions, which should be selected based on the light sensitivity of the drug itself and the intensity of the light source used. To establish and validate the analytical test method, suitable exposure conditions should be used and the test study can be terminated if excessive degradation of the sample occurs. For photostable drugs, the study can be terminated after a reasonable light exposure.

  • Confirmation tests

Under forced conditions, decomposition products that are unlikely to occur under confirmatory study conditions can be observed, and this information is useful for establishing and validating analytical methods. If the test proves that these degradation products do not arise in the confirmation study, further testing of these degradation products is not required.

If you have a requirement about our services, please contact us by phone or email, our colleagues will reply to you within three working days.

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Please note: Our products and services are not intended to be used directly in diagnostic or therapeutic procedures.
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