Routes Of Administration (Inhaled) Flashcards
1
Q
What are the main parts of the respiratory system?
A
- Upper respiratory tract: frontal sinus, larynx
- lower respiratory tract: comprising of conducting & respiratory regions.
- conducting: trachea, bronchus,bronchiole
- respiratory: terminal bronchiole, alveoli
2
Q
What are some characteristics of the lungs?
A
- Large surface area for drug absorption
- highly vascular surface promotes rapid absorption and onset of action
- air blood barrier is thinner compared to intestines allowing better drug permeability
3
Q
When is the inhalation route most commonly used?
A
- For local delivery to the lungs to treat pulmonary diseases
- administering at site of action-rapid of onset action
- lower doses = reducing side effects
- can be used to deliver drug systematically
4
Q
What are the advantages of the inhaled route?
A
- Smaller doses reducing systemic side effects and drug costs
- faster onset of action
- avoids harsh Gl environment and enzyme degradation
- avoids hepatic first pass metabolism
5
Q
What are the disadvantages of the inhaled route?
A
- Requires complex delivery devices
- aerosol devices can be difficult to use
- reproducibility of dose delivery is low due to various factors: incorrect use of device, lung capacity
- drug absorption is limited by mucus layer and clearance reduces retention time of drugs
6
Q
What devices do the inhaled route mostly use?
A
- Formulation to be an aerosol: inhaling mist to reach alveoli
- A pharmaceutical aerosol is a 2 phase system of solid particles or liquid droplets
7
Q
What is the main stages of journey for a particle in me airways?
A
- Deposition
-Dissolution - Absorption
8
Q
What are patient factors that affect particle deposition?
A
- Lung physiology: lung capacity
- breathing patterns: the larger the inhaled volume, the greater peripheral distribution of particles
- co-ordination of aerosol generation with inspiration
9
Q
What are the main physiochemical factors that can affect particle deposition
?
A
- The aerodynamic size of the drug particle which depends on size and density
- shape and physical stability of particles affects deposition
10
Q
What are the 3 main mechanisms for drug deposition?
A
- Inertial impaction
- Gravitational sedimentation
- brownian diffusion
11
Q
What is inertial impaction?
A
- Particles in the air stream with high momentum will impact on the airway walls rather than following change in air flow.
- Dominant deposition mechanism in upper airways. (equation with air stream velocity and gravitational constant)
12
Q
What is gravitational sedimentation?
A
- Sedimentation is dependent on the particle size and density
- Important for particles 1-5um in diameter.
- Occur in small airways/ alveoli
- No gravitational constant in equation
13
Q
What is Brownian Diffusion?
A
- Predominant mechanism for particles 0.5-1um
- Small particles are bombarded by random gas molecules —> causes collision with airway walls
- Common in regions where airflow is very low. Diffusion increases as particle size decreases
14
Q
What is the effect of the particle size on deposition?
A
- There is an upper and lower size limit for effective drug deposition in the lungs
- Larger mostly deposit in upper airways by inertial impaction
- Particles 1-5um deposit in lower by gravitational sedimentation
- Smaller mostly deposit in lower airways by Brownian Diffusion
- Therefore optimum size = 1-5um
15
Q
Where does the particles in the airway need to dissolve in?
A
- Mucus barrier
- Dissolution can be the rate limiting step especially poor soluble drugs
