Pulmonary drug delivery VK

Question 1

What are the applications and advantages of pulmonary drug delivery

Answer 1

• Treatment or prophylaxis of airways diseases such as COPD, cystic fibrosis
• Pulmonary administration results in a rapid onset of activity (e.g. for delivering bronchodilating drugs for the treatment of asthma)
• Smaller doses can be administered locally compared to delivery by the oral or parenteral routes
• This route is also useful where a drug is poorly absorbed orally
  -The lung may also be used as a route for delivering drugs having systemic activity

Question 2

Explain the mechanisms responsible for particle deposition in the lungs

Answer 2

Inert Impaction
- Particles hit the walls in the lungs
- particles of different diameter move through the lungs, some them will go through while some will impact the surface. so they’ll be deposited by impaction.
- This is the dominant deposition mechanism for particles > 1 micrometer
- these particles will less efficient at delivering the drug.

Gravitational sedimentation
- it is based on gravity. Particles settling under gravity will attain a constant terminal settling velocity Vt
- Depends on particle size, density and is inversely proportional to air viscosity
-Sedimentation is an important deposition mechanism for particles 0.5 – 3 micro meters , in the small airways and alveoli, for particles that have escaped deposition by impaction.

Brownian diffusion
- affects very small particles . these particles collide with each other and hit the walls of the lungs. The probability of particle deposition by diffusion increases as the particle size decreases

Question 3

Describe the physiological factors affecting particle deposition

Answer 3

Lung morphology
- The probability for particles with different sizes reaching down the alveoli is continually decreases and only the smallest possible particles will reach.

Oral versus Nasal breathing
- For nasal breathing, particles are mostly deposited in the nose and pharynx. for pulmonary delivery is by the nose.

Inspiratory flow rate
- if flow rate increases, particles are most like to be deposited higher in the airways rather than the lower parts.

Breath holding
Breath holding after inhalation enhances the deposition of particles by sedimentation and diffusion.

Question 4

List pharmaceutical factors affecting aerosol deposition

Answer 4

Aerosol velocity
Size and size distribution
Shape
Density
Physical stability

Question 5

Describe FIVE advantages of pulmonary drug delivery

Answer 5

-The dose needed to produce a pharmacological effect compared to oral dosing
- Rapid absorption rapid onset of action;
- Avoidance of GI side effects
- Avoidance of first-pass metabolism

Question 6

Describe disadvantage of Pulmonary drug delivery

Answer 6

• Complex delivery devices are required to target drugs to the airways and these devices may be inefficient;
• Aerosol devices can be difficult to use (more than 50 % adult patients have difficulty)
• Various factors affect the reproducibility of drug delivery
  Drug absorption may be limited because of mucus
• Mucociliary clearance reduces the retention time of drugs within the lungs

Question 7

What is a nebuliser

Answer 7

• its a device used to convert liquid into fine aerosol mist
• Drug is inhaled directly into your lungs via a mask or a mouthpiece.
• they deliver large volume of drug that can not be conveniently formulated into Pressurise metered dose inhaler (pMDI) or Dry powder inhalers (DPI’s)
• For people who are too ill or breathless
• for people with poor inhaler techniques

Question 8

Describe the advantages and Disadvantages of pMDI, DPI and Nebuliser

Answer 8

pMDI
Advantage
- Unit dosing;
- Inexpensive
Disadvantage
- Coordination difficulties

DPI
Advantage
- No coordination problems;
Disadvantage
- High inspiratory effort may be required;
- coughing reflex;
- less convenient than pMDI

Nebuliser
Advantage
- no coordination required
Disadvantage
- inconvenient, can’t talk or eat
- long inhalation times
- expensive
- lack of portability