Understanding prevention of photolytic degradation is essential for B.Pharm students working on drug stability and formulation. This concise introduction outlines photodegradation mechanisms, photosensitivity, photostability testing (ICH Q1B), relevant light ranges (UV and visible), common photostabilizers, antioxidants, UV absorbers, and protective packaging strategies such as amber glass and opaque laminates. It also covers formulation approaches—pH adjustment, chelators, cyclodextrin inclusion, film coatings—and analytical monitoring using HPLC and spectrophotometry. Emphasis is on practical prevention: excipient selection, controlled manufacturing, and packaging to limit potency loss and toxic photoproducts. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which mechanism primarily describes photolytic degradation of a drug molecule?
- Thermal decomposition due to high temperature
- Bond cleavage or rearrangement after absorption of light photons
- Hydrolysis in aqueous media
- Enzymatic metabolism
Correct Answer: Bond cleavage or rearrangement after absorption of light photons
Q2. The ICH guideline most relevant to photostability testing of pharmaceuticals is:
- ICH Q3A
- ICH Q1A
- ICH Q1B
- ICH Q7
Correct Answer: ICH Q1B
Q3. Which wavelength range is most commonly associated with photodegradation studies?
- Infrared: 700–1000 nm
- Microwave: >1 mm
- Ultraviolet and visible: ~200–700 nm
- Gamma rays: <0.01 nm
Correct Answer: Ultraviolet and visible: ~200–700 nm
Q4. Which packaging material is typically used to reduce UV-induced drug degradation?
- Borosilicate clear glass without additives
- Amber glass or UV-absorbing opaque laminate
- Thin transparent polyethylene film
- Clear polyethylene terephthalate (PET) with no coating
Correct Answer: Amber glass or UV-absorbing opaque laminate
Q5. Which excipient strategy is commonly used to protect a drug from light?
- Adding strong oxidizing agents
- Using photostabilizers or UV absorbers in the formulation
- Increasing free water content
- Removing antioxidants from the formula
Correct Answer: Using photostabilizers or UV absorbers in the formulation
Q6. Which antioxidant is frequently used to inhibit photooxidation in formulations?
- Sodium chloride
- Butylated hydroxytoluene (BHT)
- Calcium carbonate
- Sucrose
Correct Answer: Butylated hydroxytoluene (BHT)
Q7. How does chelation (e.g., EDTA) help prevent photodegradation?
- By neutralizing pH changes
- By binding metal ions that catalyze photooxidation
- By increasing light absorption by the API
- By acting as a primary photoinitiator
Correct Answer: By binding metal ions that catalyze photooxidation
Q8. Which formulation approach can reduce drug exposure to light in solution?
- Preparing highly dilute solutions
- Using opaque or UV-blocking containers and amber vials
- Storing solutions in clear flasks near windows
- Increasing agitation during storage
Correct Answer: Using opaque or UV-blocking containers and amber vials
Q9. Cyclodextrin inclusion complexes help prevent photodegradation by:
- Changing the pH to extreme values
- Converting the API to a gas
- Encapsulating the drug to reduce light exposure and mobility
- Acting as a strong photosensitizer
Correct Answer: Encapsulating the drug to reduce light exposure and mobility
Q10. Photostability testing should include which of the following controls?
- Only light-exposed samples without dark controls
- Dark controls and light-exposed samples under defined conditions
- Only temperature-stressed samples
- Only samples exposed to moisture
Correct Answer: Dark controls and light-exposed samples under defined conditions
Q11. Which analytical method is most commonly used to quantify photodegradation products?
- Microscopy
- High-performance liquid chromatography (HPLC)
- Rheometry
- Immediate taste testing
Correct Answer: High-performance liquid chromatography (HPLC)
Q12. A photosensitizer in a formulation typically:
- Absorbs light and transfers energy to the drug or oxygen, accelerating degradation
- Prevents light absorption by the drug
- Acts as a UV blocker
- Neutralizes free radicals directly without light
Correct Answer: Absorbs light and transfers energy to the drug or oxygen, accelerating degradation
Q13. Which coating on solid dosage forms can improve photostability?
- Transparent sugar coat with no UV filters
- Opacified film coatings containing titanium dioxide or UV absorbers
- Thin gelatin coat that is completely clear
- Coatings that increase light transmittance
Correct Answer: Opacified film coatings containing titanium dioxide or UV absorbers
Q14. Photodegradation often leads to which of the following risks?
- Increased bioavailability only
- Loss of potency and possible formation of toxic photoproducts
- Guaranteed improvement in taste
- Sterilization of the product
Correct Answer: Loss of potency and possible formation of toxic photoproducts
Q15. Which environmental factor commonly increases the rate of photodegradation?
- Reduced oxygen partial pressure
- Increased exposure to UV and visible light
- Complete darkness
- Storage at sub-zero temperatures
Correct Answer: Increased exposure to UV and visible light
Q16. Why is it important to identify photodegradation products during stability studies?
- Because products are always inert
- To assess safety, toxicity, and impact on efficacy of degradation products
- It is not necessary; only API loss matters
- Because degradation products improve solubility
Correct Answer: To assess safety, toxicity, and impact on efficacy of degradation products
Q17. Which light source is commonly used to simulate daylight in photostability chambers?
- Infrared heater lamps
- Fluorescent lamps with specified spectral distribution or xenon arc lamps
- Ordinary household incandescent bulbs only
- UV-C germicidal lamps exclusively
Correct Answer: Fluorescent lamps with specified spectral distribution or xenon arc lamps
Q18. How can pH adjustment reduce photodegradation for acid- or base-labile drugs?
- By shifting API to a more photolabile ionic form
- By converting the API into a photosensitizer
- By maintaining the drug in its more stable ionic or unionized form to reduce photolytic pathways
- By making the solution cloudy
Correct Answer: By maintaining the drug in its more stable ionic or unionized form to reduce photolytic pathways
Q19. Which statement about oxygen’s role in photodegradation is correct?
- Oxygen always inhibits photodegradation
- Oxygen can promote photooxidation by forming reactive oxygen species
- Oxygen has no effect on photochemical reactions
- Oxygen converts all photoproducts back to the parent drug
Correct Answer: Oxygen can promote photooxidation by forming reactive oxygen species
Q20. Which monitoring parameter is essential during photostability testing?
- Spectral irradiance or light dose received by the sample
- Only ambient room noise level
- Sample taste at each time point
- Magnetic field strength near the chamber
Correct Answer: Spectral irradiance or light dose received by the sample
Q21. Inclusion of UV absorbers in packaging or formulation primarily functions to:
- Increase water permeability
- Block or absorb harmful wavelengths that cause photoreactions
- Amplify light intensity inside the container
- Promote oxygen diffusion
Correct Answer: Block or absorb harmful wavelengths that cause photoreactions
Q22. Which excipient property is LEAST helpful for preventing photodegradation?
- Opacity or UV-blocking ability
- Antioxidant capacity
- Serving as a photosensitizer
- Chelation of metal ions
Correct Answer: Serving as a photosensitizer
Q23. When designing a photostability study, why include different dosage forms (solid vs. solution)?
- Different dosage forms have identical light susceptibility
- Light penetration and mobility differ; solids and solutions show different degradation pathways
- Regulations require only one form to be tested
- Solutions never degrade photolytically
Correct Answer: Light penetration and mobility differ; solids and solutions show different degradation pathways
Q24. Which type of degradation is most likely when a drug absorbs visible light and transfers energy to oxygen?
- Hydrolytic degradation
- Photooxidation via singlet oxygen or radical species
- Thermal cracking
- Enzymatic cleavage
Correct Answer: Photooxidation via singlet oxygen or radical species
Q25. What role do store-and-handle labels like “Protect from light” play?
- They are decorative only
- They guide end-users to minimize light exposure and preserve product stability
- They indicate the product must be frozen
- They require product to be opened in sunlight
Correct Answer: They guide end-users to minimize light exposure and preserve product stability
Q26. Which of the following is a non-chemical strategy to limit photodegradation?
- Add strong photosensitizers
- Use multi-layer barrier packaging and secondary cartons
- Remove opaque labels
- Increase exposure time to daylight
Correct Answer: Use multi-layer barrier packaging and secondary cartons
Q27. Photodegradation kinetics are often monitored as:
- Changes in color only, without quantification
- Decline in API concentration versus time using validated assays
- Only visual inspection at a single time point
- Measuring the change in taste profile
Correct Answer: Decline in API concentration versus time using validated assays
Q28. Which material additive can opacify a tablet film coating to reduce light penetration?
- Polysorbate without pigment
- Titanium dioxide
- Silicone oil
- Sodium chloride
Correct Answer: Titanium dioxide
Q29. Which practice during manufacturing reduces risk of photodegradation in light-sensitive APIs?
- Exposing materials to direct daylight on benches
- Controlling lighting (use of amber lights), minimizing exposure time, and using covered containers
- Leaving bulk drug in clear open trays near windows
- Using UV-C sterilization near product streams
Correct Answer: Controlling lighting (use of amber lights), minimizing exposure time, and using covered containers
Q30. The best initial step when a new degradation peak appears after light exposure is to:
- Ignore it if the assay is passing
- Characterize the photoproduct and assess its toxicological and regulatory significance
- Immediately withdraw all marketed batches without investigation
- Assume it is an analytical artifact and proceed
Correct Answer: Characterize the photoproduct and assess its toxicological and regulatory significance
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
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