W11 Routes Of Administration- Inhalation Flashcards
What is meant by an Emergency supply of salbutamol?
In an emergency, as a pharmacist working in a registered retail pharmacy, you can supply prescription-only medicines (POMs) without a prescription at the request of a relevant prescriber or a patient.
Steps of How to use a salbutamol inhaler:(pMDI)
- Remove cap (some must be squeezed at the sides to release)
- Check dose counter (if device has one)
- Hold inhaler upright and shake well
- Breathe out gently (away from inhaler)
- Put mouthpiece between teeth (without biting) and close lips to form good seal
- Start to breathe in slowly through mouth and at the same time press down firmly on canister
- Continue to breathe in slowly and deeply
- Hold breath for about 5 – 10 seconds or as long as comfortable
- While holding breath, remove inhaler from mouth
- Breathe out gently (away from inhaler)
- If more than one dose is needed, repeat all steps starting from step 3
- Replace cap
What is a pMDI?
Pressurised metered-dose inhaler
Pulmonary drug delivery- Two routes and conditions they treat
Local or topical drug administration:
* Asthma
* COPD
* Cystic fibrosis
* Pulmonary hypertension
* Lung infections?
Systemic application via the lung:
* CNS stimulation
* Anaesthetics
* Diabetes
* Pain and migraine
* Appetite suppression
Systemic: Inhaled insulin
What was the issue?
Because of the route of administration, many
respiratory adverse effects were reported,
including increased risks of respiratory infection, cough, pharyngitis, and rhinitis.
How do we deliver drugs to or via the lungs?
- Solid in gas: Solid particles suspended in air, e.g. smoke
- Liquid in gas: Liquid particles suspended in air, e.g. mist
- Gases
How does Branching of the lungs impact airflow?
- Halving the radius produces 1600% increase
in airflow resistance - 1% decrease in diameter = 4% increase in
resistance
Airflow decreases with increasing branching
Airflow in the lung is affected by which
diseases?
Obstructive lung disease:
* Asthma
* COPD
* Cystic fibrosis
Restrictive lung disease:
* Interstitial lung disease, such as idiopathic pulmonary fibrosis
* Obesity
What problem can occur in drug delivery to the lungs?
Particles entering the respiratory tract are prevented from reaching the terminal bronchioles and alveoli by mechanisms which cause them to be caught by the mucous sheath lining the tubules.
What is inertial impaction?
-Inertial impaction tends to occur in the upper airways when the velocity and mass of the particles cause them to impact the airway surface
Aerodynamic diameter
d_ae = Aerodynamic diameter
* Diameter of a sphere with the same terminal
velocity in air or some other relevant fluid as the
particle
- Aerodynamic diameter (dae) is dependent on the geometric diameter (dg), shape factor (1 for spheres) and density (ρ) of the particle
Factors Influencing lung deposition (6)
- Particle size
- Particle size distribution
- Particle density
- Particle shape
- Particle hygroscopicity- ability to absorb moisture
- Propellants
What are the function of Cilia?
Wafts drug away so reduces drug absorption
Inhaler types
- Pressurized metered-dose inhaler + (spacer)
- Accuhaler / Diskus
- Handihaler
- Respimat
- Turbohaler
- (Nebuliser)
Things to consider in manufacturing of an inhaler-quality control
- Deposition of emitted dose
- Content uniformity
- Aerodynamic particle size distribution
- Spray pattern
What are the advantages of pulmonary drug delivery?
Advantages:
* Drug delivered directly to target organ
* Lower doses may be required for optimal effect
* Rapid onset of action
* Fewer systemic side effects
* Non-invasive delivery
What are the disadvantages of pulmonary drug delivery?
- Low efficiency of delivery
- Difficulty in breath coordination, manual handling of device, or breathing through the device
- Corticosteroid use can suppress immune response
- Throat irritation is possible
Advantages of systemic delivery of drugs via the lungs
- Very rapid onset of action
- Circumvents first pass effect
- Non-invasive delivery route
- Good for biopharmaceuticals
Disadvantages of systemic delivery of drugs via the lungs
- Low efficiency of delivery
- Some patients may have difficulty using some devices (handling
and coordination) - Some patients may have difficulty breathing (through the device)
- May need very low or very exact doses or special devices
- Expensive compared with oral therapies
What are the reasons as to why the OTC ‘Inhalator’ is NOT an inhaler:
Doesn’t deliver drug to the lungs like an inhaler
* When a patient draws air into the mouth through the
mouthpiece, nicotine is vaporised and absorbed by the buccal mucosa into the bloodstream
How to use a Nicorette inhalator?
- Line up the markers and pull each end in the opposite direction
- Insert the cartridge into the mouthpiece and twist to close securely
- When you have a craving take a shallow puff about every 4 seconds or take 2 deep puffs every minute. Each cartridge lasts for approximately 40 minutes of frequent puffing
Anatomy of the mouth, throat and lung
Upper airways:
- Spheroidal
- Sinus
- Middle
- turbinateInferior
- turbinateNasopharynx
- Oropharynx
- Larynx
Central/conducting airways:
Trachea
Main bronchus
Large
subsegmental
bronchus
Small
bronchus
Bronchiole
Respiratory/peripheral/pulmonary airways:
Terminal Bronchiole
Respiratory
bronchiole
Alveolar ducts and sacs
Drug delivery to the lungs:
How are particles entering the respiratory tract hindered?
Particles entering the respiratory tract are prevented from reaching the terminal bronchioles and alveoli by mechanisms which cause them to be caught by the mucous sheath lining the tubules
Where does Inertial impaction occur?
What does it depend upon?
(for info)
In the upper airways when the velocity and mass of the particles cause them to impact the airway surface.
Whether impaction occurs depends upon:
- The particle’s momentum (dependent upon size)
- The position of the particle in the airstream of the parent branch
- The angle of bifurcation (°θ)
- Inertial impaction can be influenced to some degree by
hyperventilation - Impaction is of significance for the largest particles moving at the highest speed in the respiratory tract
- 10 μm particle has a 50% chance of impaction
- 5 μm – 20%
- 3 μm – 10%
- 1 μm – 1%
Sedimentation (for info)
- Particles suspended in a gas are subject to the vertical
gravitational force - Sedimentation is the dominant mechanism for particles
depositing in the lower/peripheral airways - Tends to be influenced by breath-holding, which allows more
time for gravity to have an effect - Important for particles 0.5 μm < daero < 5μm
- 2 μm – 55%
- 1 μm – 29%
- 0.5 μm – 10%
Diffusion (for info)
- Diffusion = dominant mechanism for particles < 0.5 μm
- The smaller the particles, the more they deposit via diffusion in the peripheral lung and alveolar space
Minor mechanisms of deposition:
* Interception for elongated particles
* Charge reflection for charged particles
What is inertial impaction?
-Inertial impaction tends to occur in the upper airways when the velocity and mass of the particles cause them to impact the airway surface
Inertial impaction is a mechanism by which particles suspended in air can be deposited in the lungs. When air carrying these particles flows through the airways of the lungs, the particles tend to continue moving in a straight line due to their inertia. As a result, they can collide with the walls of the airways and become deposited there.
This mechanism is particularly effective for particles that are larger than about 2.5 micrometers in diameter, such as pollen, dust, and some types of pollution. These particles are too large to follow the normal airflow patterns in the lungs and are instead affected more by their inertia.
Inertial impaction is one of several mechanisms by which particles can be deposited in the lungs, along with sedimentation, diffusion, and electrostatic attraction. The deposition of particles in the lungs can have negative health effects, as they can cause inflammation and other respiratory problems.
