Expiry date calculation and shelf-life determination MCQs With Answer

Introduction: This blog presents a focused set of MCQs on expiry date calculation and shelf‑life determination tailored for M.Pharm students in Quality Control & Quality Assurance. Questions cover core concepts such as stability study design (real time and accelerated), kinetic models (zero and first order), Arrhenius-based extrapolation, Q10 approach, mean kinetic temperature (MKT), ICH guidelines (Q1A, Q1E), statistical methods for shelf‑life estimation (lower one‑sided confidence limits, regression), forced degradation, retest periods versus expiration dating, and practical considerations like container closure and temperature excursions. Use these questions to test and deepen your practical and theoretical understanding of stability and shelf‑life assignment.

Q1. Which parameter defines the time required for the active pharmaceutical ingredient to degrade to 90% of its initial concentration?

• t50, the half-life
• t90, the expiry or shelf‑life limit to 90% potency
• t95, the time to reach 95% of initial concentration
• Mean kinetic temperature

Correct Answer: t90, the expiry or shelf‑life limit to 90% potency

Q2. For a drug that follows first‑order degradation kinetics, which expression gives the time to reach 90% of initial concentration (t90)?

• t90 = 0.693 / k
• t90 = ln(0.9) / k
• t90 = ln(1/0.9) / k
• t90 = (1 − 0.9) / k

Correct Answer: t90 = ln(1/0.9) / k

Q3. The Arrhenius equation is used in stability studies primarily to:

• Estimate the moisture sensitivity of an API
• Relate degradation rate constants to temperature for extrapolation
• Calculate product density changes with temperature
• Determine packaging mechanical strength

Correct Answer: Relate degradation rate constants to temperature for extrapolation

Q4. In an accelerated stability study using ICH conditions, which of the following temperature/humidity pairs is commonly used for long‑term accelerated testing of a drug product intended for storage in “zone II” climates?

• 5°C ± 3°C / not applicable
• 25°C ± 2°C / 60% RH ± 5% RH
• 40°C ± 2°C / 75% RH ± 5% RH
• 30°C ± 2°C / 65% RH ± 5% RH

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

Q5. Which ICH guideline specifically addresses the design and evaluation of stability studies for new drug substances and products?

• ICH Q9 – Quality Risk Management
• ICH Q1A(R2) – Stability Testing of New Drug Substances and Products
• ICH Q3C – Impurities: Residual Solvents
• ICH Q7 – Good Manufacturing Practice for APIs

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

Q6. When estimating shelf‑life from accelerated stability data using Arrhenius extrapolation, a major source of uncertainty is:

• Assuming zero order kinetics for all products
• Extrapolating beyond the temperature range where the degradation mechanism may change
• Using a single batch only for real‑time studies
• Ignoring humidity effects entirely

Correct Answer: Extrapolating beyond the temperature range where the degradation mechanism may change

Q7. Which statistical approach is most appropriate for assigning a conservative shelf‑life based on regression of potency versus time data?

• Use the mean predicted potency at shelf‑life
• Use the lower one‑sided 95% confidence limit of the predicted potency
• Use the upper two‑sided 99% confidence interval
• Use the standard deviation of the slope only

Correct Answer: Use the lower one‑sided 95% confidence limit of the predicted potency

Q8. Forced degradation studies are performed to:

• Determine the antimicrobial effectiveness of preservatives
• Identify degradation pathways and suitable stability‑indicating assays
• Calculate mean kinetic temperature for shipping
• Estimate dissolution profiles in different pH media

Correct Answer: Identify degradation pathways and suitable stability‑indicating assays

Q9. Which is the correct definition of retest period commonly applied to APIs?

• Time after manufacture during which the drug product must be discarded
• Time period after which an API must be retested to verify it still meets specifications
• Time needed for dissolution testing
• The time allowed for stability sampling only

Correct Answer: Time period after which an API must be retested to verify it still meets specifications

Q10. Mean kinetic temperature (MKT) is used in stability monitoring to:

• Provide a single derived temperature that represents the cumulative thermal stress over time
• Replace the need for real‑time stability studies
• Compute humidity exposure during shipping
• Determine the activation energy directly

Correct Answer: Provide a single derived temperature that represents the cumulative thermal stress over time

Q11. Which degradation order produces a straight line when concentration is plotted versus time?

• First order
• Zero order
• Second order
• Arrhenius order

Correct Answer: Zero order

Q12. A drug shows first‑order degradation with rate constant k = 0.01 day⁻¹. The calculated t90 (in days) is approximately:

• 0.105 days
• 10.5 days
• 69.3 days
• 100 days

Correct Answer: 10.5 days

Q13. The Q10 approach assumes that the reaction rate increases by a factor Q10 for every:

• 1°C increase in temperature
• 5°C increase in temperature
• 10°C increase in temperature
• 20°C increase in temperature

Correct Answer: 10°C increase in temperature

Q14. Which practice is appropriate when a short‑term temperature excursion occurs during storage of a finished product?

• Automatically discard all affected batches
• Perform a risk assessment including reanalysis and stability data review
• Extend the expiry date proportionally
• Ignore if the excursion was less than 48 hours

Correct Answer: Perform a risk assessment including reanalysis and stability data review

Q15. Matrixing and bracketing designs are used in stability studies to:

• Reduce the number of samples and time points while still providing adequate information
• Ensure each container size is tested at every time point
• Increase redundancy by testing all batches at all conditions
• Replace accelerated studies with only real‑time data

Correct Answer: Reduce the number of samples and time points while still providing adequate information

Q16. For a product with a declared shelf‑life of 24 months at 25°C, using a Q10 of 2, the approximate shelf‑life at 40°C would be:

• ~24 months
• ~8.5 months
• ~48 months
• ~12 months

Correct Answer: ~8.5 months

Q17. Which item is most critical to document when assigning an expiry date for a reconstituted or multi‑dose vial?

• The original batch manufacturing date only
• Stability data on the reconstituted product including microbial and chemical stability
• The shipping manifest
• The container color

Correct Answer: Stability data on the reconstituted product including microbial and chemical stability

Q18. According to regulatory expectations, what should a sponsor do if stability data show a trend that approaches specification limits before the intended shelf‑life?

• Assign the original shelf‑life without change
• Investigate cause, consider batch recall or shelf‑life reduction, and perform corrective actions
• Ignore the trend if only one batch shows it
• Change assay acceptance criteria

Correct Answer: Investigate cause, consider batch recall or shelf‑life reduction, and perform corrective actions

Q19. Which of the following is a correct statement about assigning expiry date for an API versus a finished product?

• APIs never have a retest period
• APIs typically receive a retest period; finished products receive an expiry date based on stability of the formulated product in its container closure
• Finished products use the API retest period directly as expiry
• APIs and finished products always use the same stability protocol

Correct Answer: APIs typically receive a retest period; finished products receive an expiry date based on stability of the formulated product in its container closure

Q20. When selecting batches for stability studies to support shelf‑life, regulatory guidance expects:

• Only one pilot batch is sufficient regardless of scale
• Representative batches including at least three primary batches manufactured by the intended commercial process
• Only small laboratory batches should be used
• Batches should be excluded if they show any early deviations

Correct Answer: Representative batches including at least three primary batches manufactured by the intended commercial process

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