Aerosols

Question 1

Three advantages of using aerosols for drug delivery.

Answer 1

*non-invasive
*rapid onset of action
*lungs provide-large surface area and readily accessible blood supply

Question 2

What is an aerosol?

Answer 2

Any system of solid or liquid particles of sufficiently small diameter to maintain some stability as a suspension in air

Question 3

What 3 factors affect aerosol deposition?

Answer 3

*physical properties of aerosol particle
*ventilation factors
*airway anatomy/lung mechanics

Question 4

What are the benefits of using smaller drug particles in aerosols?

Answer 4

*greater total lung deposition
*farther distal penetration
*more peripheral lung deposition

Question 5

What is the definition of aerodynamic diameter?

Answer 5

The diameter of a unit density sphere with the same settling velocity as the particle in question. Used to predict where in respiratory tract aerosol particles deposit.

Question 6

What is the aerodynamic diameter equation and what does each component mean ?

Answer 6

dpa=dps x square root (pp)

Dpa= aerodynamic diameter
Dps= stokes diameter of particle
Pp= particle density

Question 7

What is mass median diameter (MMD or Xg)?

Answer 7

Particle diameter that divides frequency distribution of particle in half
*50% of aerosol mass has particles with large diameter
*50% of aerosol mass has particles with smaller diameter

Question 8

What is the MMAD?

Answer 8

Mass median aerodynamic diameter - aerodynamic diameter around which the mass is centred (shape and density accounted for). Describes deposition of particles in respiratory tract.

Question 9

What are the 4 mechanisms of deposition?

Answer 9

*Inertial impaction
*gravitational sedimentation
*brownian diffusion
*electrostatic precipitation

Question 10

What is inertial impaction?

Answer 10

Refers to particles that tend to continue in their present trajectory rather than follow the curvature of the airways. They impact the airway wall. To impact the surface, particles must have enough inertial momentum to overcome drag force of gas flow on the particles.

Question 11

What is gravitational sedimentation?

Answer 11

Smaller particles (<2um) that are able to follow the airstream and penetrate the more peripheral bronchioles and alveoli. It is enhanced by breath-holding or slow steady breathing.

Question 12

What is brownian diffusion?

Answer 12

Small particles (<0.5um) are displaced by random bombardment of gas molecules and collide with airway walls. Particles deposit in distal lung.

Question 13

What is electrostatic precipitation?

Answer 13

The charge on an aerosol which can enhance the deposition of very small aerosols that have high mobility. Cause problems with spacers (plastic).

Question 14

What do ventilation factors consist of?

Answer 14

*particle velocity
*inspiratory flow- fast =increased upper airway deposition via inertial impaction. Slower=distal deposition via gravitational sedimentation.
*inspired volume= size of inspired vol affects amount of aerosol entering lungs+depth of penetration.
*breath-hold duration= enhance deposition by grav. sedimentation
*timing of aerosol delivery during inspiration

Question 15

Advantages of aerosol delivery?

Answer 15

*low doses of aerosolised drug can be delivered directly to site of action locally within airways
*drugs can be delivered to systemic circulation via distal lung leading to rapid absorption (anaesthesia)

Question 16

Advantages and disadvantages of MDI?

Answer 16

Advantages
*convenient
*less expensive than neb
*hard to contaminate
*portable

Disadvantages
*patient needs to have correct actuation
*difficult to deliver high doses

Question 17

What if cfc?

Answer 17

Chlorofluorocarbons. Non cfc propellants include hydrofluoroalkane-134a. First non cfc pMDI was salbutamol

Question 18

Advantages and disadvantages of spacers?

Answer 18

Advantages
*less patient coordination needed
*less pharyngeal deposition

Disadvantages
*more complex for some patients
*more expensive than MDI alone
*less portable

Question 19

When is it important to use a spacer with pMDI?

Answer 19

*children
*steroids-less irritation and infections

Question 20

Advantages and disadvantages and jet/ultrasonic nebulisers?

Answer 20

Advantages
*patient coordination not required
*high doses
*no cfc released

Disadvantages
*expensive
*not portable
*contamination possible
*needs prepared

Question 21

Advantages and disadvantages of DPI’s?

Answer 21

Advantages
*less patient coordination
*breath hold not needed
*no propellant needed

Disadvantages
*needs moderate to high inspiratory flow
*hard to deliver high doses
*high pharyngeal deposition

Question 22

What are the 4 types of DPI’s?

Answer 22

*disposable single unit dose- directhaler
*reusable single unit dose-spinhaler
*multi unit dose- diskus
*multi dose (reservoir)-turbohaler

Question 23

How are deposited aerosols cleared?

Answer 23

*absorbed into blood stream
*local inactivation through macrophage ingestion-slow
*lymphatic clearance-drug absorbed into lung tissue and cleared through lymphatic drainage
*mucocillary transport

Question 24

What is deep lung delivery?

Answer 24

Alternative to injection. Enables delivery of larger macromolecules not suitable for oral or transdermal delivery i.e insulin for diabetes. Reduces cost, increases patient compliance.

Question 25

Disadvantages/challenges of deep lung delivery?

Answer 25

*Barrier- ciliated mucus covered cells of airways.
*Have to deliver mg/dose not ug/dose
*most macromolecules more stable as solids than liquids