Lung Drug Delivery

Question 1

What are the three mechanisms of particle deposition in the lungs?

Answer 1

Inertial impaction
Gravitational sedimentation
Brownian diffusion

Question 2

What are the required particle sizes for the mechanisms of drug deposition?

Answer 2

For inertial impaction- greater than 5 micrometer; especially 10
For gravitational sedimentation- 0.5-3
For Brownian diffusion- smaller than 0.5 micrometer

Question 3

What is brownian diffusion

Answer 3

-collision and bombardment of small particles in the RT
Where the resultant movement that allows the particles to move from high conc to low con from the aerosol cloud to the airways
- BD is inversely proportional to particle size

Question 4

What are the key points in inertial impaction?

Answer 4

• change is airway direction/ bifurcation in the RT
• particles moving with high momentum, they impact the airway walls
• occurs in the upper airways (mouth, nose, larynx and pharynx)

Question 5

Name the key words in gravitational sedimentation

Answer 5

Constant settling velocity of the particles under GS

Particles that had escaped inertial impaction

Size, density, residence time of the particles in the RT

Smaller airways and alveoli

Question 6

MDI

Answer 6

• Drug is dissolved
  Or
  Suspended in
  Liquid propellant

-propellant flouroalkanes ( gas at rt, liquid at high pressure)

Question 7

What are the disadvantages of MDI?

Answer 7

Inefficient drug delivery
On actuation, first few droplets come out very fast

Incorrect use

Mean droplet size is 40 micrometer (shrinks as propellant evaporates)
Takes 5 secs to get to original size of micronised drug

Question 8

Does MDI+ Spacer help?

Question 9

How is dpi different from mdi

Answer 9

• No propellant
• Inhalation of finely powdered drug
• delivery larger doses
• carrier- lactose (no other excipient)
• avoid actuation or inhalation issues