Formulation of dry powder inhalers and metered dose inhalers MCQs With Answer

Formulation of dry powder inhalers and metered dose inhalers MCQs With Answer is an essential study area for B. Pharm students focusing on aerosol science, device design, particle engineering, and stability. This introduction reviews key concepts such as DPI carriers (lactose), engineered particle properties (MMAD, GSD, porosity), dispersion mechanisms, inhalation flow dependence, HFA propellants, metering valves, spray-drying and spray-freeze drying techniques, and regulatory performance tests (NGI, cascade impactor, delivered dose). Understanding formulation challenges—moisture, electrostatic charge, polymorphism, and dose uniformity—prepares you for formulation development and quality control. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the primary difference between a dry powder inhaler (DPI) and a metered dose inhaler (MDI)?

• DPI uses a propellant to aerosolize the drug while MDI relies on patient inhalation
• DPI contains liquid solutions, MDI contains dry powder
• DPI is breath-actuated and does not use propellants, whereas MDI uses a propellant to generate aerosol
• DPI always delivers larger particle sizes than MDI

Correct Answer: DPI is breath-actuated and does not use propellants, whereas MDI uses a propellant to generate aerosol

Q2. Which carrier is most commonly used in conventional carrier-based DPI formulations?

• Microcrystalline cellulose
• Lactose monohydrate
• Mannitol
• Sodium chloride

Correct Answer: Lactose monohydrate

Q3. What is the desirable mass median aerodynamic diameter (MMAD) range for particles intended to deposit in the lower respiratory tract?

• 0.1–0.5 µm
• 1–5 µm
• 5–10 µm
• 10–20 µm

Correct Answer: 1–5 µm

Q4. Which factor most strongly influences powder deagglomeration and deposition in DPI therapy?

• Ambient light
• Patient inhalation flow rate
• Tablet hardness
• Pill color

Correct Answer: Patient inhalation flow rate

Q5. Which propellant replaced chlorofluorocarbons (CFCs) in modern MDIs?

• Butane
• Hydrofluoroalkane (HFA), e.g., HFA-134a
• Propane
• Chlorodifluoromethane

Correct Answer: Hydrofluoroalkane (HFA), e.g., HFA-134a

Q6. What is the main function of the metering valve in an MDI?

• To humidify the propellant
• To filter the propellant
• To deliver a fixed dose per actuation
• To adjust particle size dynamically

Correct Answer: To deliver a fixed dose per actuation

Q7. Spray drying is commonly used in inhalation formulation to produce:

• Large crystalline tablets for oral use
• Porous, engineered microparticles with controlled density and surface properties
• Liquid suspensions for eye drops
• Solid polymeric implants

Correct Answer: Porous, engineered microparticles with controlled density and surface properties

Q8. Fine Particle Fraction (FPF) is defined as:

• The fraction of dose that is swallowed
• The percentage of emitted dose with aerodynamic diameter below a specified cutoff (commonly <5 µm)
• The total weight of formulation in the device
• The fraction of powder retained in the capsule

Correct Answer: The percentage of emitted dose with aerodynamic diameter below a specified cutoff (commonly <5 µm)

Q9. What is the role of micronized lactose fines in carrier-based DPI formulations?

• To dissolve the drug faster in the mouth
• To occupy high-energy surface sites on carrier particles and enhance drug detachment during inhalation
• To act as the primary therapeutic agent
• To increase the moisture content of the powder

Correct Answer: To occupy high-energy surface sites on carrier particles and enhance drug detachment during inhalation

Q10. The major cause of inter-patient variability in delivered dose from DPIs is:

• Ambient humidity variations only
• Device color
• Variability in patient inspiratory effort and inhalation profile
• Time of day

Correct Answer: Variability in patient inspiratory effort and inhalation profile

Q11. Why are spacers (valved holding chambers) often recommended with MDIs?

• To increase oropharyngeal deposition intentionally
• To reduce plume velocity, lower oropharyngeal deposition, and improve lung deposition
• To warm the aerosol for patient comfort
• To alter the chemical composition of the propellant

Correct Answer: To reduce plume velocity, lower oropharyngeal deposition, and improve lung deposition

Q12. What problem commonly arises after micronization of an active pharmaceutical ingredient for inhalation?

• Decreased surface area
• Increased particle cohesion and poor flow leading to agglomeration
• Complete dissolution in air
• Conversion to liquid at room temperature

Correct Answer: Increased particle cohesion and poor flow leading to agglomeration

Q13. Which instrument is standard for measuring aerodynamic particle size distribution of inhalation aerosols?

• High-performance liquid chromatograph (HPLC)
• Next Generation Impactor (NGI)
• Scanning electron microscope (SEM)
• pH meter

Correct Answer: Next Generation Impactor (NGI)

Q14. Aerodynamic diameter depends principally on which particle properties?

• Magnetic susceptibility only
• Geometric diameter and particle density (and shape)
• Color and taste
• Solubility in water only

Correct Answer: Geometric diameter and particle density (and shape)

Q15. In MDI suspensions, what is the typical purpose of adding a small amount of ethanol?

• To act as the primary therapeutic agent
• To serve as a cosolvent and improve solubility of some components and influence spray characteristics
• To make the formulation sweeter
• To solidify the propellant

Correct Answer: To serve as a cosolvent and improve solubility of some components and influence spray characteristics

Q16. What is the chief stability concern for DPI powders stored in typical environments?

• UV radiation converting lactose to oxygen
• Moisture uptake causing particle agglomeration and loss of dispersibility
• Loss of color only
• Explosive decomposition at room temperature

Correct Answer: Moisture uptake causing particle agglomeration and loss of dispersibility

Q17. Which effect is commonly observed after micronization of crystalline drug particles for inhalation?

• Decrease in surface energy and complete stabilization
• Increase in amorphous content, higher surface energy, and potentially increased hygroscopicity
• Conversion into large tablets
• Complete elimination of polymorphism

Correct Answer: Increase in amorphous content, higher surface energy, and potentially increased hygroscopicity

Q18. A narrow aerosol particle size distribution suitable for reproducible lung targeting is indicated by a geometric standard deviation (GSD) approximately:

• Greater than 3.0
• Between 2.5 and 3.5
• Less than 1.5
• Exactly 5.0

Correct Answer: Less than 1.5

Q19. The actuator orifice diameter in an MDI primarily influences:

• The chemical stability of the drug in the can
• The plume velocity and droplet/particle size distribution
• The melting point of the propellant
• The capsule rupture mechanism

Correct Answer: The plume velocity and droplet/particle size distribution

Q20. Which surface modification is commonly used to improve powder flow and reduce cohesion in DPI blends?

• Coating with polyethylene glycol (PEG-4000)
• Coating with magnesium stearate
• Adding sucrose syrup
• Heating to 200°C

Correct Answer: Coating with magnesium stearate

Q21. What distinguishes a suspension MDI from a solution MDI?

• Suspension MDI contains dissolved drug in propellant, solution MDI contains undissolved particles
• Suspension MDI contains micronized solid drug particles dispersed in propellant, solution MDI contains drug fully dissolved in the propellant/cosolvent system
• They are chemically identical
• Solution MDI always uses lactose

Correct Answer: Suspension MDI contains micronized solid drug particles dispersed in propellant, solution MDI contains drug fully dissolved in the propellant/cosolvent system

Q22. In inhaler terminology, what does “emitted dose” refer to?

• The amount of drug retained within the device after actuation
• The mass of the propellant only
• The amount of drug that exits the mouthpiece during actuation
• The total formulation mass inside the canister

Correct Answer: The amount of drug that exits the mouthpiece during actuation

Q23. Delivered dose uniformity testing for DPIs typically involves measuring dose at:

• A single arbitrary flow rate of 1 L/min
• Specified flow rates across a range (e.g., 30–90 L/min) to reflect patient variability
• Only under vacuum
• Only at extremely low temperatures

Correct Answer: Specified flow rates across a range (e.g., 30–90 L/min) to reflect patient variability

Q24. Why is electrostatic charge a problem in DPI formulations?

• It causes chemical degradation of lactose
• It makes the powder taste bitter
• It promotes adhesion of particles to device surfaces and reduces emitted dose and reproducibility
• It increases propellant vapor pressure

Correct Answer: It promotes adhesion of particles to device surfaces and reduces emitted dose and reproducibility

Q25. Besides lactose, which excipient is increasingly used as a dispersibility enhancer in spray-dried DPI particles?

• Sodium chloride
• L-leucine
• Sorbitol
• Gelatin

Correct Answer: L-leucine

Q26. Which class of propellants is used in current environmentally compliant MDIs?

• Chlorofluorocarbons (CFCs)
• Hydrofluoroalkanes (HFAs)
• Ozone-friendly chlorinated hydrocarbons
• Hydrocarbons only

Correct Answer: Hydrofluoroalkanes (HFAs)

Q27. A cascade impactor primarily provides information about:

• Chemical identity of impurities
• Aerodynamic particle size distribution and stage-wise mass deposition
• Color uniformity of the powder
• Viscosity of the propellant

Correct Answer: Aerodynamic particle size distribution and stage-wise mass deposition

Q28. Which practical measure most effectively reduces oropharyngeal deposition from an MDI?

• Warming the canister in hot water before use
• Using a spacer (valved holding chamber) with the MDI
• Shaking the canister for 2 seconds only
• Increasing the number of actuations per breath

Correct Answer: Using a spacer (valved holding chamber) with the MDI

Q29. How does high crystallinity of an inhalation drug influence DPI performance?

• Increases hygroscopicity and chemical instability
• Generally improves physical stability and reduces hygroscopicity compared to amorphous content
• Always makes particles amorphous
• Prevents aerosolization completely

Correct Answer: Generally improves physical stability and reduces hygroscopicity compared to amorphous content

Q30. Which manufacturing approaches are used to create low-density, porous particles for enhanced lung deposition in DPIs?

• Conventional granulation only
• Spray drying and spray-freeze drying to produce porous, low-density particles
• Tablet compression at high force
• Simple blending without particle engineering

Correct Answer: Spray drying and spray-freeze drying to produce porous, low-density particles

G S Sachin

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