Excipients in aerosol formulations play crucial roles in stability, delivery, and patient safety for inhaled and topical products. This concise guide introduces B.Pharm students to key excipient classes—propellants (HFA, hydrocarbons), solvents and cosolvents (ethanol, water), surfactants, preservatives (benzalkonium chloride), antioxidants, chelators (EDTA), carriers (lactose for DPI), and polymers for viscosity control. You’ll learn how excipient properties such as vapor pressure, solubility, surface tension, particle wetting, and compatibility with valves and container materials influence aerosol performance, dose uniformity, and regulatory compliance. Emphasis is on formulation design, stability testing, and safety considerations relevant to MDIs, DPIs, nebulizers, and topical aerosols. ‘Now let’s test your knowledge with 30 MCQs on this topic.’
Q1. What is the primary role of excipients in aerosol formulations?
- To provide therapeutic activity
- To enhance patient compliance only
- To aid formulation stability, delivery performance and safety
- To replace active pharmaceutical ingredient
Correct Answer: To aid formulation stability, delivery performance and safety
Q2. Which propellant class largely replaced CFCs due to ozone depletion concerns?
- Chlorofluorocarbons (CFCs)
- Hydrofluoroalkanes (HFAs)
- Carbon dioxide
- Nitrogen gas
Correct Answer: Hydrofluoroalkanes (HFAs)
Q3. Which cosolvent is commonly used in MDIs to increase drug solubility in propellant systems?
- Glycerin
- Ethanol
- Propylene glycol alginate
- Polyvinylpyrrolidone
Correct Answer: Ethanol
Q4. What is the primary function of surfactants in aerosol suspensions?
- To increase solution viscosity dramatically
- To reduce surface tension and improve wetting of drug particles
- To act as primary preservatives against microbial growth
- To increase vapor pressure of propellant
Correct Answer: To reduce surface tension and improve wetting of drug particles
Q5. Which preservative is commonly found in nasal and ophthalmic aerosol formulations?
- Benzalkonium chloride
- Sodium chloride
- Sorbitol
- Hydroxypropyl methylcellulose
Correct Answer: Benzalkonium chloride
Q6. For pulmonary delivery, what particle size range is generally optimal for deep lung deposition?
- 10–20 µm
- 5–10 µm
- 1–5 µm
- 0.01–0.1 µm
Correct Answer: 1–5 µm
Q7. Which component of a metered-dose inhaler ensures accurate liquid volume is released per actuation?
- Actuator nozzle design
- Metering valve
- Propellant cylinder material
- Container label
Correct Answer: Metering valve
Q8. In solution-type MDI formulations, how is the drug presented in the canister?
- As insoluble solid particles
- Dissolved in propellant and cosolvent
- As a dry powder mixed with lactose
- As a gas-phase solute
Correct Answer: Dissolved in propellant and cosolvent
Q9. Which excipient property most directly affects droplet breakup and initial spray plume?
- Color
- Surface tension
- pH indicator
- Melting point
Correct Answer: Surface tension
Q10. What is the main purpose of compatibility testing for excipients in aerosol formulations?
- To determine marketing strategy
- To check interactions between excipients, drug, container and valve that may affect stability
- To set the retail price
- To measure inhalation flow rate
Correct Answer: To check interactions between excipients, drug, container and valve that may affect stability
Q11. Which antioxidant is often used in aerosol formulations to prevent oxidative degradation?
- Butylated hydroxytoluene (BHT)
- Polyethylene glycol
- Calcium carbonate
- Hydrochloric acid
Correct Answer: Butylated hydroxytoluene (BHT)
Q12. Lactose is commonly used as which type of excipient in DPIs?
- Preservative
- Carrier
- Propellant
- Surfactant
Correct Answer: Carrier
Q13. Which of the following excipients can increase formulation viscosity to reduce fine particle fraction?
- Viscosity modifiers like hydroxypropyl methylcellulose
- Volatile propellants like HFA
- Low-molecular-weight alcohols
- Inert gases like nitrogen
Correct Answer: Viscosity modifiers like hydroxypropyl methylcellulose
Q14. Why are hydrocarbon propellants (propane, butane) sometimes restricted in pharmaceutical aerosols?
- They are non-volatile
- They are flammable and potentially explosive
- They cannot generate pressure
- They cause immediate degradation of all drugs
Correct Answer: They are flammable and potentially explosive
Q15. What is the role of chelating agents like EDTA in aerosol formulations?
- To increase surface tension
- To sequester metal ions that catalyze degradation
- To act as a primary aerosol propellant
- To enhance flavor
Correct Answer: To sequester metal ions that catalyze degradation
Q16. Which aerosol device does NOT rely on a propellant to generate an aerosol?
- Metered-dose inhaler (MDI)
- Dry powder inhaler (DPI)
- Propellant spray can
- Pressurized nasal spray
Correct Answer: Dry powder inhaler (DPI)
Q17. Which container component is a common source of leachables affecting aerosol safety?
- Aluminum can wall
- Valve gasket made from elastomeric rubber
- Actuator label ink
- External cardboard carton
Correct Answer: Valve gasket made from elastomeric rubber
Q18. Humectants such as glycerin are added to topical aerosols to:
- Increase vapor pressure
- Retain moisture on the skin and prevent dryness
- Act as primary surfactants
- Provide antimicrobial activity
Correct Answer: Retain moisture on the skin and prevent dryness
Q19. Creaming in an aerosol emulsion is primarily caused by:
- Chemical reaction between propellant and drug
- Density differences and poor emulsifier performance
- Sterilization at high temperature
- Excessive particulate micronization
Correct Answer: Density differences and poor emulsifier performance
Q20. Which excipient class is most important for stabilizing suspended drug particles in an MDI?
- Colorants
- Suspending agents and surfactants
- Flavoring agents
- Non-volatile gases
Correct Answer: Suspending agents and surfactants
Q21. What is the effect of increasing ethanol content in an HFA MDI formulation?
- Decreases drug solubility in propellant
- Acts as a cosolvent to increase drug solubility but may alter plume and throat deposition
- Makes the formulation non-pressurized
- Eliminates need for a metering valve
Correct Answer: Acts as a cosolvent to increase drug solubility but may alter plume and throat deposition
Q22. Which test specifically assesses uniformity of dose delivered from an aerosol device?
- pH test
- Delivered dose uniformity (DDU) test
- Melting point determination
- Viscosity at 100°C
Correct Answer: Delivered dose uniformity (DDU) test
Q23. Silicone oil is commonly used in aerosol valves as a:
- Propellant
- Valve lubricant to ensure smooth actuation
- Primary solvent for drug
- Preservative
Correct Answer: Valve lubricant to ensure smooth actuation
Q24. Which container material is often preferred for compatibility and barrier properties in MDIs?
- Paperboard
- Aluminum
- Wood
- Textile fiber
Correct Answer: Aluminum
Q25. The major regulatory reason for replacing CFC propellants was:
- Higher production cost
- Ozone layer depletion and international phase-out
- Poor spray performance
- Lack of availability of raw materials
Correct Answer: Ozone layer depletion and international phase-out
Q26. In formulation design, which excipient helps improve powder flow and dispersibility in DPIs?
- Lactose as carrier
- Benzalkonium chloride
- Butylated hydroxytoluene
- Synthetic perfumes
Correct Answer: Lactose as carrier
Q27. Surfactants in aerosol formulations can prevent which undesirable phenomenon in suspensions?
- Excessive boiling point
- Particle aggregation and settling
- Increase in container volume
- Automatic sterilization
Correct Answer: Particle aggregation and settling
Q28. Which excipient property should be evaluated to avoid corrosion or degradation of metal canisters?
- pH and corrosivity of solvent system
- Color intensity
- Odor threshold
- Thermal conductivity
Correct Answer: pH and corrosivity of solvent system
Q29. Which excipient class is used to chelate trace metals and prevent catalytic breakdown of actives?
- Chelating agents (e.g., EDTA)
- Sweeteners
- Propellants
- Flavoring agents
Correct Answer: Chelating agents (e.g., EDTA)
Q30. Which regulatory agency issues guidance relevant to aerosol delivery systems and excipient safety for pharmaceuticals?
- Local municipal council
- Food and Drug Administration (FDA)
- International Postal Union
- World Tourism Organization
Correct Answer: Food and Drug Administration (FDA)
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