Introduction: Stability studies of aerosols are essential for B.Pharm students to understand how pressurized metered‑dose inhalers (pMDIs), dry powder inhalers (DPIs), and nasal sprays retain physical and chemical integrity over time. Key concepts include propellant behavior, particle size distribution, mass median aerodynamic diameter (MMAD), container‑closure compatibility, chemical degradation, assay by HPLC/GC, microbial control, and ICH accelerated and long‑term testing conditions. Practical stability evaluation covers plume geometry, spray pattern, valve performance, leakage, and in‑use stability to ensure safety, efficacy, and dose uniformity. Mastery of these topics supports formulation optimization and regulatory compliance. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the primary aim of stability studies for aerosol formulations?
- To determine patient preference
- To assess long‑term physical and chemical integrity and ensure consistent dose delivery
- To measure manufacturing cost
- To evaluate advertising claims
Correct Answer: To assess long‑term physical and chemical integrity and ensure consistent dose delivery
Q2. Which parameter most directly characterizes aerodynamic behavior of particles from inhalers?
- Viscosity
- pH
- Mass median aerodynamic diameter (MMAD)
- Surface tension
Correct Answer: Mass median aerodynamic diameter (MMAD)
Q3. Which analytical technique is commonly used for assay and impurity profiling in aerosol stability studies?
- UV-visible spectroscopy without separation
- HPLC with validated stability‑indicating method
- Thermogravimetric analysis (TGA)
- Polarimetry
Correct Answer: HPLC with validated stability‑indicating method
Q4. Which test evaluates uniformity of delivered dose from a metered‑dose inhaler?
- Spray pattern only
- Delivered dose uniformity (DDU) or multiple actuation content assay
- Leak test only
- pH stability test
Correct Answer: Delivered dose uniformity (DDU) or multiple actuation content assay
Q5. In aerosol stability, what does “container‑closure compatibility” assess?
- Color of the label
- Interactions between formulation and container/valve affecting stability and dose
- Marketing shelf display
- Patient instructions readability
Correct Answer: Interactions between formulation and container/valve affecting stability and dose
Q6. Which environmental condition is NOT typically used in ICH long‑term stability studies?
- 25°C ± 2°C / 60% RH ± 5% RH
- 30°C / 65% RH for certain climates
- 40°C / 75% RH (accelerated)
- −80°C ultra‑low temperature
Correct Answer: −80°C ultra‑low temperature
Q7. What is the significance of cascade impactor testing for inhalation products?
- Measures propellant composition
- Determines aerodynamic particle size distribution and fine particle fraction
- Assesses container label adhesion
- Evaluates taste masking
Correct Answer: Determines aerodynamic particle size distribution and fine particle fraction
Q8. Which change indicates physical instability in a pMDI formulation?
- Change in assay by 0.01% only
- Phase separation, precipitation, or clogging of valve
- Minor label wear
- Stable pressure reading
Correct Answer: Phase separation, precipitation, or clogging of valve
Q9. What role do preservatives play in multi‑dose nasal or aerosol formulations?
- Enhance flavor
- Prevent microbial contamination during in‑use period
- Increase aerosol velocity
- Act as propellants
Correct Answer: Prevent microbial contamination during in‑use period
Q10. Which test assesses valve and can leakage in pressurized aerosols?
- Spray pattern test
- Leak test such as pressure decay or helium leak detection
- Viscosity measurement
- Organoleptic testing
Correct Answer: Leak test such as pressure decay or helium leak detection
Q11. Photostability testing for aerosols is performed to evaluate:
- Effect of light exposure on chemical degradation and label fading
- Taste change under light
- Valve corrosion only
- Packaging aesthetics
Correct Answer: Effect of light exposure on chemical degradation and label fading
Q12. Which propellant shift significantly affected aerosol formulation strategy historically?
- Water to ethanol
- CFCs (chlorofluorocarbons) to HFAs (hydrofluoroalkanes)
- Switch from oxygen to nitrogen
- Use of helium as propellant
Correct Answer: CFCs (chlorofluorocarbons) to HFAs (hydrofluoroalkanes)
Q13. What is “in‑use stability” for aerosols?
- Stability during manufacturing only
- Stability after opening/first use under recommended conditions for intended duration
- Stability at cryogenic storage
- Stability in shipping containers only
Correct Answer: Stability after opening/first use under recommended conditions for intended duration
Q14. Which parameter measures spray dispersion pattern visually for topical aerosols?
- MMAD measurement
- Plume geometry and spray pattern
- pKa determination
- Moisture sorption isotherm
Correct Answer: Plume geometry and spray pattern
Q15. A stability‑indicating method must be able to:
- Only quantify the main drug peak without impurities
- Separate and quantify drug and degradation products accurately
- Measure only physical changes
- Be qualitative only
Correct Answer: Separate and quantify drug and degradation products accurately
Q16. Which degradation mechanism is commonly monitored in aerosol formulations?
- Polymerization due to propellant incompatibility
- Hydrolysis, oxidation, and photodegradation of active ingredient
- Radioactive decay
- Enzymatic digestion by patient enzymes
Correct Answer: Hydrolysis, oxidation, and photodegradation of active ingredient
Q17. Why is headspace pressure measurement important in pressurized aerosols?
- To test label adhesion
- To monitor propellant loss and container integrity
- To evaluate taste
- To measure particle size
Correct Answer: To monitor propellant loss and container integrity
Q18. Which of the following is a critical quality attribute for DPIs during stability testing?
- Propellant evaporation rate
- Moisture uptake affecting powder flow and dispersion
- Valve leak rate
- Color of propellant
Correct Answer: Moisture uptake affecting powder flow and dispersion
Q19. What does “priming” an inhaler refer to in stability/use evaluation?
- Cleaning the label
- Actuating a device to prepare correct dose delivery after storage
- Freezing before use
- Removing the propellant
Correct Answer: Actuating a device to prepare correct dose delivery after storage
Q20. Which regulatory guideline is most applicable to pharmaceutical stability studies including aerosols?
- ICH Q1A (R2) stability testing of new drug substances and products
- WHO GMP only
- Guideline for cosmetics
- Occupational safety guidelines
Correct Answer: ICH Q1A (R2) stability testing of new drug substances and products
Q21. During accelerated stability, which observation suggests instability?
- No change in assay and particle size
- Significant increase in degradation products and loss of delivered dose
- Label remains intact
- Valve functions normally
Correct Answer: Significant increase in degradation products and loss of delivered dose
Q22. Which test helps evaluate the tendency of formulation components to adsorb onto container or valve surfaces?
- Adsorption/compatibility studies using stressed storage and extractables/leachables testing
- Only microbial testing
- Only visual inspection
- Packaging drop test
Correct Answer: Adsorption/compatibility studies using stressed storage and extractables/leachables testing
Q23. Microbial contamination in multi‑dose aerosols is most likely assessed by:
- Sterility testing and preservative efficacy testing (PET)
- MMAD measurement
- Plume geometry only
- pH of the packaging ink
Correct Answer: Sterility testing and preservative efficacy testing (PET)
Q24. Which is a common method to measure particle size distribution for nasal sprays?
- HPLC assay
- Laser diffraction or spray droplet sizing
- Organoleptic testing
- Moisture sorption analysis
Correct Answer: Laser diffraction or spray droplet sizing
Q25. What is the purpose of leak detection during stability testing of aerosols?
- To increase propellant strength
- To ensure container integrity and prevent loss of product or contamination
- To evaluate taste change
- To test colorfastness
Correct Answer: To ensure container integrity and prevent loss of product or contamination
Q26. Which excipient property is crucial to control in DPIs for good stability?
- High volatility
- Low hygroscopicity and good flowability
- High color intensity
- Low melting point
Correct Answer: Low hygroscopicity and good flowability
Q27. Residual propellant amount is monitored because:
- It affects product aesthetics only
- Changes alter pressure, dose delivery, and spray characteristics
- It controls taste masking
- It is unrelated to stability
Correct Answer: Changes alter pressure, dose delivery, and spray characteristics
Q28. Which packaging test is relevant to aerosol stability during transport?
- Plume geometry test
- Vibration and shock testing to simulate transport stress
- HPLC assay only
- Photostability only
Correct Answer: Vibration and shock testing to simulate transport stress
Q29. When designing a stability protocol for an aerosol intended for hot climates, you should consider:
- Only cold storage
- Appropriate climatic zone conditions (e.g., 30°C/65% RH) and robustness testing
- Only photostability
- Only microbial tests
Correct Answer: Appropriate climatic zone conditions (e.g., 30°C/65% RH) and robustness testing
Q30. Which result would most likely require reformulation of an aerosol product?
- Minor label misprint
- Progressive loss of delivered dose and increase in degradation impurities under recommended storage
- Stable MMAD and plume geometry
- Unchanged headspace pressure
Correct Answer: Progressive loss of delivered dose and increase in degradation impurities under recommended storage
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