Inhalable therapeutic aerosols

Question 1

What is an aerosol?

Answer 1

A relatively stable suspension of solid or liquid particles in a gaseous medium

Question 2

What do aerosol aerodynamic properties depend on?

Answer 2

size, shape and density

Question 3

What 3 shapes do aerosols come in?

Answer 3

Spherical
Fibrous
Aggregates

Question 4

What is the definition of pharmaceutical aerosols?

Answer 4

Colloidal systems of very finely subdivided liquid or solid pharmaceutical active particles dispersed in and surrounded by a gas

Question 5

What 6 factors control drug delivery to the lung?

Answer 5

Formulation
Device
Patient activation
Lung deposition
Dissolution
Absorption

Question 6

The majority of harmful particles are what size?

Answer 6

3 microns or less

Question 7

What is the main extrinsic cause of asthma?

Answer 7

House-dust mite faeces

Question 8

What are the advantages of using inhalation therapy for local delivery?

Answer 8

Drug delivered directly to site of action
Drug action onset is rapid
Less drug in systemic circulation
Lower doses required

Question 9

What are the advantages of inhalation therapy for systemic delivery?

Answer 9

Extensive blood supply gives potential for rapid absorption into systemic circulation
Avoids first pass metabolism
Increased bioavailability

Question 10

What size particles deposit in alveoli?

Answer 10

0.5-2 microns

Question 11

What size particles deposit in the bronchus?

Answer 11

2-7microns

Question 12

What size particles deposit in the trachea?

Answer 12

7-10microns

Question 13

What 3 factors control aerosol deposition?

Answer 13

Aerosol properties
Mode of inhalation
Patient relating factors

Question 14

Impaction occurs for particles of what size?

Answer 14

> 10microns

Question 15

Sedimintation occurs for particles of what size?

Answer 15

2-3microns

Question 16

Diffusion occurs for particles of what size?

Answer 16

<1micron

Question 17

What is inertial impaction?

Answer 17

Impaction caused by the tendency of particles to continue to move in a straight line

Question 18

Inertial impaction perdominately occurs for what?

Answer 18

Large particles when the gas airstream is fast, changing direction or turbulent

Question 19

Where does inertial impaction mainly occur?

Answer 19

Oropharynx, larynx or at bifurcations

Question 20

What is gravitational sedimentation dependent on?

Answer 20

Terminal settling velocity of particle

Question 21

When does gravitational sedimentation occur?

Answer 21

Where air velocity in respiratory tract is low and residence time is high

Question 22

What is diffusion (Brownian motion)?

Answer 22

Particles bombarded by air molecules giving rise to a ‘random walk’

Question 23

When is difffusion dominant?

Answer 23

As particle size approaches the mean free path of the air molecules

Question 24

What can improve diffusion deposition efficiency?

Answer 24

High residence time (Breath holding)

Question 25

What is interception?

Answer 25

Deposition where particles contact walls

Question 26

What is electrostatic deposition?

Answer 26

Charge particles repel-increase in migration towards airway walls

Question 27

The world market for asthma drugs is expected to exceed what by 2015?

Answer 27

$25 billion

Question 28

What are the 3 main types of inhalable devices?

Answer 28

pMDI DPI Nebuliser

Question 29

What is the aim of nebulisers?

Answer 29

Reproducibly deliver correct dose to site of action with minumum waste

Question 30

Many nebulisers deliver as little as what of the target dose?

Answer 30

10%

Question 31

What was the dominant nebuliser system on the market pre 2000?

Answer 31

Pneumatic nebulisers

Question 32

What are the 4 componenets of pneumatic nebulisers?

Answer 32

Disposable unit Compressor Interfaces Valves/holding chamber

Question 33

What are the pros and cons of pneumatic nebulisers?

Answer 33

``` Cheap Small particle sizes Variable performance Dead volume Lower output Portability ```

Question 34

What are the components of high frequency ultrasonic nebulisers?

Answer 34

``` Electronic power source Liquid reservoir Synthetic piezoelectric ceramic disc Air fan Mouthpiece ```

Question 35

What are the pros and cons of ultrasonic nebulisers?

Answer 35

``` Reproducible Small particle size High output Small and quiet Low aerosol inertia Size increase at end of life Expensive Heats solution to 40degC Poor for suspensions ```