Photolytic degradation MCQs With Answer

Photolytic degradation MCQs With Answer is a focused set of questions designed for B.Pharm students to deepen understanding of drug photostability. This resource covers mechanisms of photolysis, Type I and Type II pathways, common photolabile functional groups, effects of UV/VIS wavelengths, role of photosensitizers and excipients, and analytical approaches like HPLC and LC-MS for photoproduct identification. Emphasis is placed on photostability testing (ICH Q1B), kinetics, formulation strategies, and packaging to minimize photodegradation. Questions combine conceptual depth with practical scenarios encountered in formulation and quality control. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is photolytic degradation in the context of pharmaceuticals?

• The breakdown of drug molecules caused by exposure to light
• The thermal decomposition of drugs at high temperatures
• The enzymatic degradation of drugs in the body
• The loss of drug potency due to humidity

Correct Answer: The breakdown of drug molecules caused by exposure to light

Q2. Which wavelength range is most commonly associated with photodegradation of drug substances?

• Infrared (700–1000 nm)
• Visible and near UV (290–700 nm)
• Microwave (1 mm–1 m)
• Gamma rays (>10 pm)

Correct Answer: Visible and near UV (290–700 nm)

Q3. What is a photosensitizer in pharmaceutical photochemistry?

• A compound that absorbs light and transfers energy to the drug, promoting degradation
• A packaging film that blocks UV light
• An antioxidant that prevents oxidation
• A stabilizer that increases the drug’s melting point

Correct Answer: A compound that absorbs light and transfers energy to the drug, promoting degradation

Q4. Which photochemical mechanism involves generation of singlet oxygen?

• Type I photoreaction
• Type II photoreaction
• Thermal rearrangement
• Photohydrolysis only

Correct Answer: Type II photoreaction

Q5. Which functional group is commonly photolabile and prone to photodegradation?

• Alkane (saturated C–C single bonds)
• Nitroaromatic group
• Tert-butyl ether (very stable)
• Saturated ester (completely inert)

Correct Answer: Nitroaromatic group

Q6. Quantum yield in photochemistry refers to:

• The number of photons emitted by a lamp per second
• The ratio of molecules reacted to photons absorbed
• The molar mass of the drug divided by its absorbance
• The intensity of visible light only

Correct Answer: The ratio of molecules reacted to photons absorbed

Q7. Which of the following excipients can act as a photosensitizer?

• Microcrystalline cellulose
• Riboflavin (vitamin B2)
• Mannitol
• Sodium chloride

Correct Answer: Riboflavin (vitamin B2)

Q8. In forced photostability testing per ICH Q1B, the purpose is to:

• Evaluate drug dissolution under light
• Identify photodegradation pathways and photoproducts
• Measure microbial contamination after light exposure
• Determine melting point changes under light

Correct Answer: Identify photodegradation pathways and photoproducts

Q9. Which analytical technique is most useful for identifying low-level photoproducts?

• Polarimetry
• LC-MS (liquid chromatography–mass spectrometry)
• Thermogravimetric analysis (TGA)
• Refractive index measurement

Correct Answer: LC-MS (liquid chromatography–mass spectrometry)

Q10. How does oxygen typically influence photodegradation?

• It always inhibits photodegradation by quenching excited states
• It can promote photodegradation via formation of reactive oxygen species
• It converts all photoproducts back to the parent drug
• It has no effect on photochemical reactions

Correct Answer: It can promote photodegradation via formation of reactive oxygen species

Q11. Photodegradation kinetics of many drugs under constant irradiance often follow which order?

• Zero-order kinetics
• Pseudo-first-order kinetics
• Second-order kinetics
• Michaelis–Menten kinetics

Correct Answer: Pseudo-first-order kinetics

Q12. Which packaging choice best protects a photosensitive liquid formulation?

• Clear glass bottle
• Amber glass bottle
• Transparent PET bottle
• Metal cap only, no light protection

Correct Answer: Amber glass bottle

Q13. Actinometry is used to:

• Measure microbial contamination in light-exposed samples
• Quantify the number of photons in a photochemical experiment
• Determine the melting point under irradiation
• Assess osmotic pressure of solutions

Correct Answer: Quantify the number of photons in a photochemical experiment

Q14. A photostable formulation aims to:

• Maximize drug absorption of UV light
• Minimize formation of harmful photoproducts
• Increase the drug’s fluorescence
• Promote photochemical reactions for activation

Correct Answer: Minimize formation of harmful photoproducts

Q15. Which group of drugs is particularly susceptible to photodegradation leading to loss of potency?

• Drugs with extended conjugated systems (e.g., enones, azo compounds)
• Tertiary alkanes with no chromophores
• Highly saturated hydrocarbons only
• Inert inorganic salts

Correct Answer: Drugs with extended conjugated systems (e.g., enones, azo compounds)

Q16. Which measure can reduce photodegradation in solid oral dosage forms?

• Increase tablet size only
• Use opaque/UV-blocking coatings or capsules
• Store at high temperatures
• Expose to light during packaging

Correct Answer: Use opaque/UV-blocking coatings or capsules

Q17. Photohydrolysis refers to:

• Light-induced cleavage of bonds in the presence of water
• Thermal breakdown in dry conditions
• Enzymatic hydrolysis in the liver
• Formation of hydrates without light

Correct Answer: Light-induced cleavage of bonds in the presence of water

Q18. Which common excipient can act as a photocatalyst when present as nanoparticles?

• Talc
• Titanium dioxide (TiO2)
• Lactose monohydrate
• Sodium alginate

Correct Answer: Titanium dioxide (TiO2)

Q19. What is the role of antioxidants in photostability?

• They absorb UV light and generate singlet oxygen
• They scavenge free radicals and reduce oxidative photodamage
• They increase the refractive index of formulations
• They catalyze bond cleavage under light

Correct Answer: They scavenge free radicals and reduce oxidative photodamage

Q20. Which parameter directly affects a drug’s susceptibility to photodegradation?

• Molar absorptivity at incident wavelengths
• Number of chiral centers only
• Solubility in nonpolar solvents only
• Tablet hardness exclusively

Correct Answer: Molar absorptivity at incident wavelengths

Q21. During photostability testing, why are control samples protected from light?

• To test effects of humidity only
• To distinguish changes caused by light from other degradation pathways
• To accelerate photodegradation artificially
• To increase sample temperature for thermal degradation

Correct Answer: To distinguish changes caused by light from other degradation pathways

Q22. Which photoproduct identification approach helps determine molecular weights and fragmentation patterns?

• Visual inspection of color change
• Mass spectrometry (MS)
• Melting point determination
• Polarimetry

Correct Answer: Mass spectrometry (MS)

Q23. What is the effect of pH on photodegradation in solution?

• pH has no effect on photochemical reactions
• Ionization state can change absorption properties and reactivity
• Only solid-state drugs are affected by pH
• Lower pH always prevents photodegradation

Correct Answer: Ionization state can change absorption properties and reactivity

Q24. Which statement distinguishes photolysis from hydrolysis?

• Photolysis involves light; hydrolysis involves water-driven bond cleavage
• Photolysis requires enzymes; hydrolysis requires light
• Both are identical processes
• Hydrolysis only happens in solids

Correct Answer: Photolysis involves light; hydrolysis involves water-driven bond cleavage

Q25. Which experimental control helps determine if a formulation component is a photosensitizer?

• Compare photodegradation with and without the component under identical light
• Measure melting point with the component
• Test only at elevated temperature without light
• Check solubility differences exclusively

Correct Answer: Compare photodegradation with and without the component under identical light

Q26. What is an important reason to characterize primary photoproducts?

• They always enhance therapeutic activity
• To assess potential toxicity, potency loss, and structure for stability strategies
• To increase the product’s shelf weight
• Because photoproducts are always volatile

Correct Answer: To assess potential toxicity, potency loss, and structure for stability strategies

Q27. How can film coatings reduce photodegradation of tablets?

• By acting as inert fillers only
• By incorporating UV absorbers or using opaque pigments
• By increasing tablet porosity
• By making tablets more hygroscopic

Correct Answer: By incorporating UV absorbers or using opaque pigments

Q28. What is the primary concern when a drug forms reactive photoproducts in vivo?

• They improve taste
• They may cause phototoxicity or alter safety profile
• They always speed up absorption beneficially
• They only change color without safety implications

Correct Answer: They may cause phototoxicity or alter safety profile

Q29. Which in vitro method can help simulate sunlight exposure for photostability testing?

• Use of a temperature-controlled oven only
• Solar simulator or xenon arc lamp with appropriate filters
• Storage in a dark refrigerator
• UV-C lamp only without filtering

Correct Answer: Solar simulator or xenon arc lamp with appropriate filters

Q30. If a drug shows significant photodegradation during development, which formulation approach is appropriate?

• Remove all excipients to simplify formulation
• Use light-protective packaging, opaque coatings, antioxidants, or change formulation pH
• Increase exposure to light to build tolerance
• Ignore photostability if dissolution is acceptable

Correct Answer: Use light-protective packaging, opaque coatings, antioxidants, or change formulation pH

G S Sachin

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.

Mail- Sachin@pharmacyfreak.com