Stability testing of drug substances MCQs With Answer

Stability testing of drug substances MCQs With Answer

Introduction: Stability testing is a cornerstone of pharmaceutical quality assurance, ensuring that drug substances retain their safety, potency, purity and physical characteristics throughout their intended shelf-life. For M.Pharm students, mastering stability principles — including ICH guidelines, stress testing, kinetics, packaging impacts, and design of stability protocols — is essential for regulatory submissions and formulation development. This quiz collection focuses on in-depth concepts such as forced degradation, stability-indicating methods, Arrhenius-based extrapolation, bracketing/matrixing, and environmental influences (temperature, humidity, light, and oxygen). Each question is followed by the correct answer to aid active learning and quick revision for exams and practical applications.

Q1. What is the primary objective of stability testing of a drug substance?

• To determine the toxicity profile of impurities
• To establish shelf-life and recommended storage conditions
• To validate manufacturing equipment
• To determine pharmacokinetics in humans

Correct Answer: To establish shelf-life and recommended storage conditions

Q2. Which ICH guideline specifically addresses stability testing of new drug substances and drug products?

• ICH Q2(R1): Validation of Analytical Procedures
• ICH Q1A(R2): Stability Testing of New Drug Substances and Products
• ICH Q3A(R2): Impurities in New Drug Substances
• ICH Q5C: Stability of Biotechnological Products

Correct Answer: ICH Q1A(R2): Stability Testing of New Drug Substances and Products

Q3. According to ICH, what are the standard long-term stability conditions often used for drug substances in temperate zones (Zone II)?

• 30°C ±2°C / 75% ±5% RH
• 25°C ±2°C / 60% ±5% RH
• 40°C ±2°C / 25% ±5% RH
• 5°C ±3°C / 30% ±5% RH

Correct Answer: 25°C ±2°C / 60% ±5% RH

Q4. Which ICH guideline describes the photostability testing of new drug substances and products?

• ICH Q1B: Photostability Testing of New Drug Substances and Products
• ICH Q1C: Stability Testing for New Dosage Forms
• ICH Q3B: Photochemical Impurity Assessment
• ICH Q2: Analytical Method Validation

Correct Answer: ICH Q1B: Photostability Testing of New Drug Substances and Products

Q5. What are the typical accelerated stability testing conditions recommended by ICH?

• 5°C ±3°C / ambient RH
• 25°C ±2°C / 60% ±5% RH
• 40°C ±2°C / 75% ±5% RH
• 30°C ±2°C / 45% ±5% RH

Correct Answer: 40°C ±2°C / 75% ±5% RH

Q6. What does “bracketing” mean in the context of stability study design?

• Testing all strength and container sizes at every time point
• Testing only the extreme strengths, container sizes, or conditions to represent the intermediate levels
• Performing stability studies using accelerated conditions only
• Testing only the median sample in a batch

Correct Answer: Testing only the extreme strengths, container sizes, or conditions to represent the intermediate levels

Q7. What is the primary purpose of forced degradation (stress testing) of a drug substance?

• To determine the exact market shelf-life under normal conditions
• To identify likely degradation products and develop stability-indicating analytical methods
• To increase the potency of the drug substance
• To sterilize the drug substance prior to testing

Correct Answer: To identify likely degradation products and develop stability-indicating analytical methods

Q8. Which statement best describes a stability-indicating analytical method?

• An assay that measures total UV absorbance of a formulation
• An analytical method that quantitatively measures the active ingredient without interference from degradation products, impurities or excipients
• A method used only for dissolution testing
• An assay that detects only impurities above 5%

Correct Answer: An analytical method that quantitatively measures the active ingredient without interference from degradation products, impurities or excipients

Q9. The Arrhenius equation is used in stability studies primarily to:

• Estimate the effect of humidity on photostability
• Predict temperature dependence of degradation rates and extrapolate shelf-life
• Determine the pH at which degradation is maximal
• Measure light-induced reactions

Correct Answer: Predict temperature dependence of degradation rates and extrapolate shelf-life

Q10. Which reaction kinetics corresponds to a constant degradation rate independent of concentration?

• First-order kinetics
• Second-order kinetics
• Zero-order kinetics
• Pseudo-first-order kinetics

Correct Answer: Zero-order kinetics

Q11. What does the term “retest period” for a drug substance mean?

• The time after which a finished product must be withdrawn from the market
• The period after which a drug substance must be retested to ensure it still meets specified quality attributes
• The expiry date printed on the finished product label
• The time required to perform forced degradation studies

Correct Answer: The period after which a drug substance must be retested to ensure it still meets specified quality attributes

Q12. Which container-closure property most directly affects the stability of moisture-sensitive drug substances?

• Oxygen transmission rate (OTR)
• Light transmission
• Water vapour transmission/permeability (WVTR)
• Thermal conductivity

Correct Answer: Water vapour transmission/permeability (WVTR)

Q13. Which of the following is a physical change rather than a chemical degradation pathway?

• Hydrolysis
• Oxidation
• Photodegradation
• Recrystallization (polymorphic conversion)

Correct Answer: Recrystallization (polymorphic conversion)

Q14. Which environmental factor most strongly stresses moisture-sensitive solid drug substances during stability studies?

• Low temperature (refrigeration)
• High humidity
• High oxygen concentration
• Low light exposure

Correct Answer: High humidity

Q15. ICH Q1B specifies light exposure values for photostability testing. What are the recommended minimum exposures?

• 500,000 lux hours visible and 100 Wh/m² near UV
• 1.2 million lux hours visible and 200 Wh/m² near UV
• 2.5 million lux hours visible and 500 Wh/m² near UV
• 100,000 lux hours visible and 20 Wh/m² near UV

Correct Answer: 1.2 million lux hours visible and 200 Wh/m² near UV

Q16. Degradation accelerated by trace metal ions (e.g., iron, copper) is usually categorized as:

• Hydrolytic degradation
• Oxidative degradation
• Photolytic degradation
• Thermal decomposition

Correct Answer: Oxidative degradation

Q17. Which statement correctly defines “shelf-life” of a drug product?

• The time from manufacture during which the product is expected to remain within approved specifications when stored under defined conditions
• The time required to manufacture the product
• The time allowable for marketing authorization after submission
• The time before the first stability sample is taken

Correct Answer: The time from manufacture during which the product is expected to remain within approved specifications when stored under defined conditions

Q18. What does “matrixing” design in stability studies entail?

• Testing all time points for all strengths and packaging configurations
• Testing a subset of samples at each time point such that each sample is represented across the study but not all combinations are tested at every time point
• Using only accelerated conditions for all samples
• Randomly discarding samples from the stability program

Correct Answer: Testing a subset of samples at each time point such that each sample is represented across the study but not all combinations are tested at every time point

Q19. Why are simulated shipping condition studies performed as part of stability assessment?

• To evaluate the effect of temperature and humidity excursions during distribution on product quality
• To accelerate chemical degradation beyond typical storage conditions for regulatory submission
• To reduce the number of long-term samples required
• To determine the optimal manufacturing batch size

Correct Answer: To evaluate the effect of temperature and humidity excursions during distribution on product quality

Q20. At what stage should formal stability studies for a new drug substance ideally begin?

• Only after regulatory approval is granted
• As early as possible during development and continued through clinical development and submission
• Only during commercial manufacture
• Only when impurities exceed 1% in batch analysis

Correct Answer: As early as possible during development and continued through clinical development and submission

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