Stability kinetics and stability testing MCQs With Answer

Stability kinetics and stability testing MCQs With Answer is designed to help M. Pharm students master the concepts behind drug degradation, kinetic modeling, and regulatory stability protocols. This quiz covers reaction orders, Arrhenius behavior, Q10, shelf-life estimation, pH–rate profiles, solid-state stability, and ICH guidelines for real-time, accelerated, and photostability testing. You will also find questions on forced degradation, moisture effects, autoxidation, packaging interactions, and statistical evaluation of stability data. Each MCQ provides focused options and a clear answer to strengthen both theoretical understanding and practical decision-making in formulation and quality by design. Use this set to revise key principles and align your preparation with the MPH 103T syllabus.

Q1. On an Arrhenius plot, which relationship correctly describes the slope when plotting ln k versus 1/T?

• Slope equals -Ea/R
• Slope equals Ea/R
• Intercept equals -Ea/R
• Slope equals -R/Ea

Correct Answer: Slope equals -Ea/R

Q2. If a degradation process has Q10 = 2, the rate at 40°C relative to 25°C is approximately:

• 1.5×
• 2.0×
• 2.8×
• 4.0×

Correct Answer: 2.8×

Q3. Which linear plot is diagnostic of first-order degradation kinetics?

• Plot of log C vs time is linear with slope -k/2.303
• Plot of C vs time is linear with slope -k
• Plot of 1/C vs time is linear with slope k
• Plot of C^0.5 vs time is linear

Correct Answer: Plot of log C vs time is linear with slope -k/2.303

Q4. Drug degradation in an aqueous suspension often follows apparent zero-order kinetics because:

• The drug concentration in solution remains at its solubility due to a solid reservoir
• Degradation occurs only in the solid state
• Stirring converts first-order to zero-order
• Particle size growth eliminates dissolution

Correct Answer: The drug concentration in solution remains at its solubility due to a solid reservoir

Q5. For a first-order degradation, the time to 90% label claim (t90) is given by:

• t90 = 0.105/k
• t90 = 0.1 C0/k
• t90 = 0.693/k
• t90 = ln 2 / k0

Correct Answer: t90 = 0.105/k

Q6. As per ICH Q1A(R2), the standard accelerated condition for solid oral products in rigid containers is:

• 25°C/60% RH
• 30°C/65% RH
• 40°C/75% RH
• 50°C/20% RH

Correct Answer: 40°C/75% RH

Q7. ICH Q1B specifies that confirmatory photostability testing should expose samples to at least:

• 1.2 million lux hours and 200 W·h/m^2 near-UV
• 120,000 lux hours and 20 W·h/m^2 near-UV
• 2 million lux hours and 400 W·h/m^2 near-UV
• 500,000 lux hours and 50 W·h/m^2 near-UV

Correct Answer: 1.2 million lux hours and 200 W·h/m^2 near-UV

Q8. A typical target extent of degradation for forced degradation (stress testing) studies is:

• 0.5–2%
• 5–20%
• 30–40%
• Complete degradation

Correct Answer: 5–20%

Q9. Which functional group in drug molecules is most susceptible to base-catalyzed hydrolysis?

• Ether
• Ester
• Nitro
• Nitrile

Correct Answer: Ester

Q10. Which strategy most effectively reduces autoxidation catalyzed by trace metals?

• Add a chelating agent such as EDTA
• Increase dissolved oxygen
• Adjust pH to neutrality
• Add a surfactant to improve wetting

Correct Answer: Add a chelating agent such as EDTA

Q11. In a pH–rate (log k vs pH) profile showing both acid and base catalysis, maximum stability occurs at:

• The pH where k is maximum
• Any pH above 10
• The pH where k is minimum
• pH equal to the pKa of the drug

Correct Answer: The pH where k is minimum

Q12. Which statement about solid-state stability is true?

• Amorphous solids are generally more reactive than crystalline forms due to higher free energy
• Crystals are always less stable than amorphous forms
• Raising temperature below Tg increases molecular mobility dramatically
• Moisture increases Tg of amorphous solids

Correct Answer: Amorphous solids are generally more reactive than crystalline forms due to higher free energy

Q13. Deliquescence of a hygroscopic drug salt occurs when:

• RH falls below the glass transition RH
• Temperature rises above Tg
• Ambient RH exceeds its critical relative humidity (CRH)
• The product is stored under nitrogen

Correct Answer: Ambient RH exceeds its critical relative humidity (CRH)

Q14. According to ICH Q1E, stability data from multiple primary batches may be pooled for regression when:

• Slopes differ significantly (p < 0.05)
• There is no significant difference in slopes across batches (e.g., p > 0.25 for slope equality)
• The batches are from different manufacturing sites
• Pooling is always prohibited

Correct Answer: There is no significant difference in slopes across batches (e.g., p > 0.25 for slope equality)

Q15. If a drug shows first-order degradation with a half-life of 2.0 years at 25°C, the first-order rate constant k at 25°C is approximately:

• 0.346 year^-1
• 0.231 year^-1
• 0.693 year^-1
• 2.303 year^-1

Correct Answer: 0.346 year^-1

Q16. For two products with the same k at 25°C but different activation energies (Ea1 > Ea2), which statement is true?

• The product with higher Ea will degrade faster at lower temperatures
• The product with higher Ea will show a larger increase in rate at elevated temperature
• Both products will have identical temperature dependence
• Activation energy does not affect temperature dependence

Correct Answer: The product with higher Ea will show a larger increase in rate at elevated temperature

Q17. For aqueous products in semipermeable containers, ICH Q1A(R2) recommends accelerated testing at:

• 25°C/60% RH
• 30°C/75% RH
• 40°C/ NMT 25% RH to assess water loss
• 50°C/ ambient RH

Correct Answer: 40°C/ NMT 25% RH to assess water loss

Q18. In ICH Q1B photostability testing, which control must be included?

• A dark control protected by aluminum foil or opaque covering
• A control stored at 50°C
• A control flushed with nitrogen
• No controls are required

Correct Answer: A dark control protected by aluminum foil or opaque covering

Q19. A common cause of loss of antimicrobial preservative effectiveness during stability is:

• Partitioning/sorption of preservative into plastic packaging materials
• Decrease in headspace oxygen
• Increase in buffer capacity
• Use of amber glass containers

Correct Answer: Partitioning/sorption of preservative into plastic packaging materials

Q20. In-use stability studies for multidose products primarily assess:

• Performance under freezing conditions only
• Changes in assay, degradation products, and microbial quality during and after repeated opening/withdrawal over the labeled in-use period
• Only organoleptic attributes after first opening
• Only container closure integrity

Correct Answer: Changes in assay, degradation products, and microbial quality during and after repeated opening/withdrawal over the labeled in-use period

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