Physical factors influencing drug degradation MCQs With Answer

Physical factors influencing drug degradation determine how formulations lose potency, change appearance, or form harmful impurities during storage and handling. For B. Pharm students, mastering concepts like temperature effects, humidity and water activity, light/photodegradation, oxygen permeability, particle size, polymorphism, glass transition (Tg), and packaging is essential for predicting stability and designing robust products. Key keywords: physical factors influencing drug degradation, temperature, humidity, photostability, Arrhenius kinetics, glass transition, polymorphism, packaging, accelerated stability, moisture sorption, desiccants. This concise primer links theory to practical stability testing and formulation strategies. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which physical factor most directly increases the rate of most chemical degradation reactions in a drug product?

• Humidity
• Temperature
• Particle size
• Light exposure

Correct Answer: Temperature

Q2. The Arrhenius equation relates reaction rate constants to which physical parameter?

• Relative humidity
• Activation energy
• Temperature
• Light intensity

Correct Answer: Temperature

Q3. A Q10 value of 2 for a drug degradation process means:

• The rate doubles for every 10°C rise in temperature
• The rate halves for every 10°C rise in temperature
• The shelf-life doubles every 10°C rise in temperature
• The activation energy is 2 kJ/mol

Correct Answer: The rate doubles for every 10°C rise in temperature

Q4. Which physical parameter best describes the amount of unbound water available to participate in hydrolytic degradation?

• Bulk moisture content (%)
• Water activity (aw)
• Relative humidity of the room
• Deliquescence point

Correct Answer: Water activity (aw)

Q5. A hygroscopic excipient in a tablet formulation is most likely to cause:

• Reduced solubility of the API
• Increased moisture uptake and hydrolysis
• Enhanced photostability
• Decreased surface area

Correct Answer: Increased moisture uptake and hydrolysis

Q6. Deliquescence refers to:

• Transition from crystalline to amorphous state
• Substance absorbing moisture and dissolving into a solution
• Light-induced breakdown of molecules
• Conversion of polymorphs on heating

Correct Answer: Substance absorbing moisture and dissolving into a solution

Q7. Which packaging strategy best minimizes photodegradation of a light-sensitive drug?

• Permeable plastic bottle
• Amber glass or opaque packaging
• High oxygen-permeable film
• Cardboard box without inner barrier

Correct Answer: Amber glass or opaque packaging

Q8. ICH Q1B is a guideline primarily concerned with:

• Accelerated temperature-humidity testing
• Photostability testing of new drug substances and products
• Microbial limits for APIs
• Packaging validation for cold-chain drugs

Correct Answer: Photostability testing of new drug substances and products

Q9. Which analytical technique is most useful to detect polymorphic transitions that may affect stability?

• UV-Vis spectroscopy
• X-ray powder diffraction (XRPD)
• pH meter
• High performance liquid chromatography (HPLC)

Correct Answer: X-ray powder diffraction (XRPD)

Q10. A drug stored above its glass transition temperature (Tg) in the amorphous state is likely to:

• Become more physically stable with less molecular mobility
• Exhibit increased molecular mobility and faster chemical degradation
• Crystallize immediately and stop degrading
• Be unaffected by temperature relative to Tg

Correct Answer: Exhibit increased molecular mobility and faster chemical degradation

Q11. Particle size reduction typically increases degradation risk because it:

• Decreases surface area exposed to environment
• Increases surface area and can increase surface-mediated degradation
• Changes pH of solid particles
• Eliminates polymorphic forms

Correct Answer: Increases surface area and can increase surface-mediated degradation

Q12. Ostwald ripening in suspensions refers to:

• Smaller particles dissolving and redepositing on larger particles
• Photochemical cross-linking of molecules
• Conversion of amorphous to crystalline drug
• Hydrolysis of esters in solution

Correct Answer: Smaller particles dissolving and redepositing on larger particles

Q13. Critical relative humidity (CRH) for a drug substance is defined as:

• The humidity below which the substance will sublimate
• The humidity above which the salt or crystal will uptake moisture and dissolve
• The humidity needed for photostability testing
• The humidity at which the glass transition occurs

Correct Answer: The humidity above which the salt or crystal will uptake moisture and dissolve

Q14. Which of the following physical factors can promote eutectic formation and subsequent liquefaction in a solid mixture?

• Low temperature storage
• High relative humidity and intimate contact between components
• Use of amber glass packaging
• Increasing particle size

Correct Answer: High relative humidity and intimate contact between components

Q15. Freeze–thaw cycling during storage primarily risks which physical change in liquid formulations?

• Permanent increase in pH
• Aggregation, phase separation, or protein denaturation
• Conversion to crystalline solids
• Complete elimination of oxygen

Correct Answer: Aggregation, phase separation, or protein denaturation

Q16. Which property of packaging material is most important to prevent moisture-driven degradation?

• Optical clarity
• Water vapor transmission rate (WVTR)
• Color fastness
• Thermal conductivity

Correct Answer: Water vapor transmission rate (WVTR)

Q17. Which test condition is typical for accelerated stability studies addressing physical factors per pharmacopeial guidance?

• 5°C and 20% RH
• 40°C and 75% RH
• 100°C and 0% RH
• Room temperature light exposure only

Correct Answer: 40°C and 75% RH

Q18. Photodegradation that involves an excited drug molecule reacting directly with light is termed:

• Indirect photodegradation
• Thermal degradation
• Direct photodegradation
• Hydrolytic degradation

Correct Answer: Direct photodegradation

Q19. In solid dosage forms, which factor can accelerate degradation by increasing local mobility at the surface?

• Low surface area
• Presence of amorphous domains on the surface
• High crystallinity throughout
• Use of non-hygroscopic excipients only

Correct Answer: Presence of amorphous domains on the surface

Q20. Which mitigation is most appropriate to limit oxygen-induced degradation in filled vials?

• Use of transparent plastic without barrier
• Headspace nitrogen purging and oxygen scavengers
• Increasing storage temperature
• Storing under high humidity

Correct Answer: Headspace nitrogen purging and oxygen scavengers

Q21. Which measurement technique can quantify moisture uptake kinetics of a powdered drug at controlled RH?

• Differential scanning calorimetry (DSC)
• Dynamic vapor sorption (DVS)
• Gas chromatography (GC)
• UV-Vis spectroscopy

Correct Answer: Dynamic vapor sorption (DVS)

Q22. A polymorph conversion to a more stable form during storage usually results in:

• Increased solubility and faster dissolution
• Decreased solubility and possible loss of bioavailability
• Immediate photodegradation
• Increased water activity

Correct Answer: Decreased solubility and possible loss of bioavailability

Q23. Which of the following is a practical formulation approach to reduce moisture-induced degradation?

• Inclusion of hygroscopic fillers
• Use of desiccants and moisture-barrier primary packaging
• Increasing tablet porosity
• Storing products in thin, high-permeability films

Correct Answer: Use of desiccants and moisture-barrier primary packaging

Q24. Which physical factor influences both chemical degradation kinetics and physical stability of amorphous solids?

• Light wavelength only
• Temperature relative to Tg
• Particle color
• Compression force during tableting only

Correct Answer: Temperature relative to Tg

Q25. Which scenario best explains why micronized drug powder may show higher degradation in stability tests?

• Micronization reduces surface area and exposure
• Micronization increases surface defects, reactivity, and surface area
• Micronization stabilizes polymorphs permanently
• Micronization removes moisture completely

Correct Answer: Micronization increases surface defects, reactivity, and surface area

Q26. Which physical change is commonly monitored by DSC to assess stability-related transitions?

• Loss on drying percentage
• Melting point and glass transition temperature
• pH shift in solution
• UV absorbance peak shift

Correct Answer: Melting point and glass transition temperature

Q27. Which factor is LEAST likely to be classified as a physical factor influencing degradation?

• Relative humidity
• Catalytic impurity introduced by metal ions
• Light exposure
• Temperature fluctuations

Correct Answer: Catalytic impurity introduced by metal ions

Q28. Temperature cycling can accelerate degradation by:

• Causing repeated thermal stress leading to moisture ingress, phase changes, or mechanical damage
• Eliminating all oxygen from packaging
• Reducing water activity permanently
• Lowering the activation energy to zero

Correct Answer: Causing repeated thermal stress leading to moisture ingress, phase changes, or mechanical damage

Q29. Which excipient property would you examine to predict its impact on moisture-related stability?

• Glass transition temperature alone
• Hygroscopicity and moisture sorption isotherm
• Optical rotation
• Intrinsic viscosity only

Correct Answer: Hygroscopicity and moisture sorption isotherm

Q30. During photostability testing, observation of new impurity peaks in HPLC combined with changes in UV spectra suggests:

• Physical aggregation only
• Chemical photodegradation producing new degradants
• Only reversible conformational changes without chemical change
• Complete protection by packaging

Correct Answer: Chemical photodegradation producing new degradants