Introduction: Pharmaceutical aerosols are drug formulations in which fine solid or liquid particles are dispersed in a gas for topical, nasal, or pulmonary delivery. Understanding the clear definition and practical classification of pharmaceutical aerosols—pressurized metered-dose inhalers (pMDIs), dry powder inhalers (DPIs), nebulizers, and topical aerosols—is essential for B.Pharm students. Key concepts include propellants (CFC vs HFA), particle size distribution (MMAD, FPF), aerosol physics, valve and actuator design, filling methods, stability, and regulatory quality tests. Mastery of these topics strengthens formulation development and clinical performance evaluation. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. What is the best definition of a pharmaceutical aerosol?
- A solution of drug in water intended for injection
- A suspension or solution of solid or liquid particles in a gas for therapeutic or diagnostic use
- A topical cream that evaporates on the skin
- A tablet that disintegrates into fine particles in the stomach
Correct Answer: A suspension or solution of solid or liquid particles in a gas for therapeutic or diagnostic use
Q2. Which classification correctly groups common pharmaceutical aerosol dosage forms?
- Tablets, capsules, ointments
- pMDIs, DPIs, nebulizers, topical aerosols
- Solutions, emulsions, suspensions
- Suppositories, implants, patches
Correct Answer: pMDIs, DPIs, nebulizers, topical aerosols
Q3. Which component is NOT typically part of a pressurized metered-dose inhaler (pMDI)?
- Propellant
- Metering valve
- Actuator
- Rotor-stator homogenizer
Correct Answer: Rotor-stator homogenizer
Q4. What is the main role of a propellant in a pMDI?
- To act as a preservative for the drug
- To dissolve the valve materials
- To generate the driving force that ejects and disperses droplets or particles
- To reduce particle size by milling
Correct Answer: To generate the driving force that ejects and disperses droplets or particles
Q5. Which propellant replaced CFCs due to environmental concerns?
- Hydrochlorofluorocarbon (HCFC-22)
- Hydrofluoroalkane (HFA)
- Nitrous oxide
- Dimethyl ether only
Correct Answer: Hydrofluoroalkane (HFA)
Q6. Which parameter best describes the aerodynamic behavior of aerosol particles in the respiratory tract?
- Solubility in water
- Mass median aerodynamic diameter (MMAD)
- Melting point
- Vapor pressure
Correct Answer: Mass median aerodynamic diameter (MMAD)
Q7. What MMAD range is generally considered optimal for deep lung (alveolar) deposition?
- 0.01–0.1 µm
- 1–5 µm
- 10–50 µm
- 100–300 µm
Correct Answer: 1–5 µm
Q8. Which instrument is commonly used to measure aerodynamic particle size distribution for inhalation aerosols?
- High-performance liquid chromatograph (HPLC)
- Cascade impactor
- UV–Vis spectrophotometer
- pH meter
Correct Answer: Cascade impactor
Q9. What does Fine Particle Fraction (FPF) represent in aerosol characterization?
- The percentage of particles < 5 µm that are likely to reach the lower airways
- The amount of preservative in the formulation
- The fraction of particles that remain in the actuator
- The volume of propellant per canister
Correct Answer: The percentage of particles < 5 µm that are likely to reach the lower airways
Q10. Which inhaler type depends primarily on patient inspiratory flow to aerosolize the drug?
- Pressurized MDI (pMDI)
- Dry powder inhaler (DPI)
- Jet nebulizer
- Atomizer spray pump
Correct Answer: Dry powder inhaler (DPI)
Q11. In a pMDI, the valve’s metering chamber most directly affects which attribute?
- Color of the aerosol
- Delivered dose uniformity per actuation
- Melting point of the drug
- Propellant vapor pressure
Correct Answer: Delivered dose uniformity per actuation
Q12. Which filling method is commonly used for pMDIs containing liquefied gas propellants?
- Cold filling (under pressure)
- Spray drying
- Lyophilization
- Electrospinning
Correct Answer: Cold filling (under pressure)
Q13. Which of the following is an advantage of HFA propellants over CFCs?
- Higher ozone depletion potential
- Lower aerosol performance in all cases
- Environmentally safer with negligible ozone depletion potential
- They are solid at room temperature
Correct Answer: Environmentally safer with negligible ozone depletion potential
Q14. What is the principal mechanism by which nebulizers generate aerosols?
- Condensation of vapor into particles
- Mechanical atomization via jets, ultrasonic vibration or mesh
- Chemical reaction producing gas bubbles
- Electrostatic attraction causing particle formation
Correct Answer: Mechanical atomization via jets, ultrasonic vibration or mesh
Q15. Which quality test is essential for regulatory approval of a pMDI regarding dose delivery over the canister life?
- Thermal degradation test
- Delivered dose uniformity (DDU) across actuations
- Osmolality measurement
- Plasticizer migration assay
Correct Answer: Delivered dose uniformity (DDU) across actuations
Q16. How does actuator orifice diameter affect aerosol performance in pMDIs?
- Smaller orifice always increases particle size
- Orifice diameter influences plume velocity and droplet size, affecting deposition
- Orifice size only changes color of spray
- Orifice diameter has no effect on aerosol characteristics
Correct Answer: Orifice diameter influences plume velocity and droplet size, affecting deposition
Q17. Which statement about DPIs is TRUE?
- DPIs use propellants to eject powder
- DPIs are breath-actuated and require powder deagglomeration by inspiratory flow
- DPIs deliver liquid emulsions only
- DPIs cannot deliver drugs to the lungs
Correct Answer: DPIs are breath-actuated and require powder deagglomeration by inspiratory flow
Q18. What is a potential formulation challenge for suspension-based pMDIs?
- Maintaining drug particle suspension stability and preventing agglomeration or sedimentation
- Excessive solubility of drug in propellant
- Evaporation of solid drug particles into gas
- Inability to compress the formulation into tablets
Correct Answer: Maintaining drug particle suspension stability and preventing agglomeration or sedimentation
Q19. Which test assesses the spray shape immediately as aerosol exits the actuator?
- Spray pattern and plume geometry assessment
- Cascade impaction
- Solubility test
- pH titration
Correct Answer: Spray pattern and plume geometry assessment
Q20. What is the main environmental concern associated with older CFC propellants?
- They increase greenhouse warming more than CO2
- Ozone layer depletion leading to increased UV radiation
- They corrode metal canisters rapidly
- They cause instant toxicity to inhalation users
Correct Answer: Ozone layer depletion leading to increased UV radiation
Q21. Metered-dose inhaler canisters are often made from which material and why?
- Glass, because it is permeable to propellant gases
- Polystyrene, because it is flexible
- Aluminum, for corrosion resistance and compatibility with propellants
- Wood, for biodegradability
Correct Answer: Aluminum, for corrosion resistance and compatibility with propellants
Q22. Which excipient in aerosol formulations helps stabilize suspensions and prevent aggregation?
- Surfactants (e.g., lecithin)
- Heavy metals
- Strong acids
- Alcohols only
Correct Answer: Surfactants (e.g., lecithin)
Q23. Laser diffraction measures which aerosol property directly?
- Aerodynamic diameter under inertial forces
- Optical (geometric) particle size distribution based on light scattering
- Chemical composition of particles
- Propellant ozone depletion potential
Correct Answer: Optical (geometric) particle size distribution based on light scattering
Q24. Which factor reduces the delivered dose from a pMDI during use?
- Consistent shaking before actuation when required
- Holding canister upright between actuations as recommended
- Increased temperature leading to higher vapor pressure and leak
- Proper priming prior to first use
Correct Answer: Increased temperature leading to higher vapor pressure and leak
Q25. What is the purpose of adding cosolvents like ethanol to HFA formulations?
- To polymerize the drug inside the canister
- To increase solubility of some drugs and modify spray characteristics
- To act as a metering valve lubricant only
- To eliminate the need for actuators
Correct Answer: To increase solubility of some drugs and modify spray characteristics
Q26. Which aerosol generation method produces the finest droplets for topical sprays?
- Mechanical atomization with a fine nozzle
- Hand rubbing of liquid on skin
- Filling into a large open container
- Creating foam by mixing two solids
Correct Answer: Mechanical atomization with a fine nozzle
Q27. Which regulatory test evaluates microbial safety for multi-dose aqueous aerosols?
- Antimicrobial preservative efficacy test
- Particle size analysis
- Flame point test
- Chromatography purity test
Correct Answer: Antimicrobial preservative efficacy test
Q28. How does humidity typically affect dry powder inhaler (DPI) performance?
- High humidity can cause powder agglomeration and reduced aerosolization
- Humidity has no effect because powders are inert
- Higher humidity always improves dispersion
- Humidity converts powder to gas, increasing delivery
Correct Answer: High humidity can cause powder agglomeration and reduced aerosolization
Q29. Which statement describes the concept of “metered-dose” in pMDIs?
- Each actuation releases a variable dose depending on pressure
- Each actuation delivers a reproducible, pre-measured quantity of formulation
- The dose is measured by patient breath only
- The dose is determined by canister color
Correct Answer: Each actuation delivers a reproducible, pre-measured quantity of formulation
Q30. Which factor is critical for achieving consistent lung deposition from an inhaler?
- Matching particle aerodynamic size, device design, and patient inhalation technique
- Using the heaviest possible excipients
- Maximizing canister volume regardless of formulation
- Ensuring the drug is completely insoluble in any solvent
Correct Answer: Matching particle aerodynamic size, device design, and patient inhalation technique
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