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Pharmaceutics > Inhaled Route > Flashcards

Inhaled Route Flashcards

1
Q

What is the inhaled route for?

A

Local action

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2
Q

What diseases can the inhaled route treat?

A

Asthma + COPD

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3
Q

Why do you administer a drug at site of action?

A

Rapid onset of action

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4
Q

What is the benefit of using smaller doses?

A

Reduces side effects + cost

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5
Q

Why is the inhaled route easy?

A

Large SA for absorption
Highly vascularised surface
Air-blood barrier thinner compared to other barriers

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6
Q

Why is it good to have highly vascularised surface?

A

Rapid absorption + onset of action

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7
Q

Why is it good that the air-blood barrier is thin?

A

Better drug permeability

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8
Q

What are the advantages?

A

Smaller doses can be used
Rapid absorption
Avoids GI environment
Avoids hepatic 1st-pass metabolism

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9
Q

Why is it good that it avoids the GI environment?

A

Minimises chemical + enzymatic drug degradation

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10
Q

What are the disadvantages?

A

Requires complex delivery devices = high cost
Can be difficult to use
Reproducibility of dose delivery = low
Dug absorption may be limited by mucus layer

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11
Q

What is a pharmaceutical aerosol?

A

2-phase system of solid particles or liquid droplets dispersed in air

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12
Q

Why is it good that an pharmaceutical aerosol is small?

A

Considerable stability as suspension

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13
Q

What happens in drug route?

A

Deposition —> dissolution —> absorption

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14
Q

What patient factors affect particle deposition?

A

Lung physiology
Breathing patterns
Coordination of aerosol with inspiration
Breath holding

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15
Q

What happens if a larger vol is inhaled?

A

Great peripheral distribution of particles + increased inhalation flow

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16
Q

Why do you ask patients to hold their breath?

A

Enhances deposition

17
Q

What physiochemical factors affect particle deposition?

A

Aerodynamic size of drug particle

Shape + physical stability

18
Q

What are the three particle deposition mechanisms?

A

Inertial impaction
Gravitational sedimentation
Brownian diffusion

19
Q

Describe inertial impaction

A

Particles within air stream, having high momentum, impacts on airway’s walls rather than following changing air flow

20
Q

Where is inertial impaction dominant?

A

Upper airways

> 5 micro m tho

21
Q

What is gravitational sedimentation dependent on?

A

Particle size, density + residence time in airways

22
Q

What size particles is gravitational sedimentation important for?

A

1-5 micro m

23
Q

Where does gravitational sedimentation occur?

A

Small airways + alveoli = lower velocity

24
Q

What size particles are important for Brownian diffusion?

A

0.5-1 micro m

25
Q

Describe what happens in Brownian diffusion

A

Bombarded by random gas molecules + produce Brownian motion

= particles collide with airway walls

26
Q

What happens to Brownian diffusion as particle size decreases?

A

Increases

27
Q

What must the aerosolised powder do first?

A

Dissolve in mucus layer before absorption

28
Q

What can dissolution be for poorly soluble drugs?

A

Rate limiting step

29
Q

What happens once the drug is in solution?

A

Diffuse across mucus layer + enter aq environment of epithelial lining

30
Q

What is mucociliary clearance?

A

Mucus layer constantly propelled along airways by rhythmic beating of cilia on epithelial cells

31
Q

What happens to particles deposited in ciliated conducting airways?

A

Cleared by mucociliary clearance

32
Q

What happens to particles deposited in alveolar region?

A

Cleared by macrophages

33
Q

When can drug absorption only take place?

A

If dissolution is faster than clearance

34
Q

What is hydrophobic material absorption dependent on?

A

Their O/W coefficient

35
Q

Which compounds are poorly absorbed?

A

Hydrophilic

36
Q

Which form is better absorbed?

A

Unionised form

37
Q

What can the rate of absorption be influenced by?

A

Formulation

38
Q

What are the different inhalation devices?

A

Pressurised metered dose inhaler (pMDIs)
Dry powder inhalers (DPIs)
Nebulisers

Pharmaceutics (21 decks)

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