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S2 Case 3 - asthma & COPD > Inhaled Route of Delivery: Dry Powder Inhaler > Flashcards

Inhaled Route of Delivery: Dry Powder Inhaler Flashcards

1
Q

How do they deliver to the drugs?

A

Moves over static powder bed then fluidised
Fluidised particles aggregated by strong aerodynamic force
Enters airway + drug separates from carrier

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2
Q

Where the particles go if they are larger?

A

Throat

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3
Q

Where will the particles go if they are smaller?

A

Deep into respiratory tract

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4
Q

What happens if deep sharp breath?

A

Increased turbulent air
= increased inertial impaction

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5
Q

What happens if controlled respiratory flow rate?

A

Drug move slower + follow air flow to lower respiratory tract

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6
Q

What size are micronized powders?

A

2-5 micrometres

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7
Q

Why must they be shaken?

A

Powders never completely homogenous
= affect dose uniformity

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8
Q

What does micronization do?

A

Reduce drug size
Improve homogeneity + control particle size

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9
Q

How is micronization achieved?

A

Jet milling

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10
Q

Describe jet milling

A

Material fed into shallow circular grinding chamber
High velocity
Turbulence = particle bombarding
= larger particles concentrated at periphery of chamber
Finer particles leave with air stream

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11
Q

What are the powder factors to consider when formulating DPIs?

A

Crystallinity
Hygroscopicity
Polydispersity
Aerodynamic diameter

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12
Q

What is crystallinity?

A

Packing within structure
= increased packing = increased stability BUT decreased dissolution

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13
Q

What happens in crystallinity?

A

Powders transfer to lower energy state
Choose most stable polymorph

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14
Q

What is hygroscopicity?

A

Ability to take up moisture

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15
Q

What happens in crystallinity?

A

Take up moisture
= disrupt crystal structure
= effect dissolution profile + crystallisation

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16
Q

What is polydispersity?

A

Range of particles around the mold

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17
Q

What happens in polydispersity?

A

Inhaled powders = multi-modal
= NOT all particles all same size
= poly dispersed

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18
Q

What is aerodynamic diameter?

A

Influence where particle lands in lung

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19
Q

Why is lactose used?

A

Decrease drug cohesiveness

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20
Q

Describe what happens with excipient lactose

A

Drugs adhere to larger carrier particles by weak electrostatic forces
Particles fly off larger carrier particles
Carrier deposits + remains in mouth
Still feel powder left in mouth

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21
Q

What does adhesion + detachment depend on?

A

Morphology of particle surfaces + surface energies

22
Q

What can a carrier with rough surface do?

A

Hold micronized drug too strongly during storage
= increase overall aerodynamic size

23
Q

What can a carrier with smooth surface do?

A

Increased dispersion during inhalation
BUT may not stay mixed

24
Q

What is an approach to smooth vs rough surface?

A

Mix rough carrier particles first with micronized carrier then with micronized drug
= drug free to detach

25
Q

What is the aim of powder mixing?

A

Achieve homogeneity

26
Q

What is the major challenge?

A

Inhaler resistance + inspiratory flow rate

27
Q

What happens when a patient inhales?

A

Diaphragm generates decreased pressure
= air flow

28
Q

How is increased flow rate achieved?

A

Decreased resistive device

29
Q

What happens if there is a narrow inlet?

A

Increased turbulence
Rapid airflow
= deposition in the throat

30
Q

What happens if there is narrow flow stream?

A

Increased velocity
= increased improvement to device performance

31
Q

What happens if there is high resistance?

A

Better performance

32
Q

What is the problem with high resistance?

A

Paediatric + elderly patients may have difficulties with insufficient IFR

33
Q

Why is a rapid airflow required?

A

Increases particle deagglomeration
BUT at same time increase oropharyngeal deposition + reduce dose delivered to drug

34
Q

What can DPIs be?

A

Unit-dose or multi-dose

35
Q

Describe Spinhaler

A

Contains sodium cromoglicate
1st DPI
Unit-dose

36
Q

Describe how each dose in Spinhaler is contained?

A

In hard gelatin capsule
Placed individually into device prior to use

37
Q

Describe how the Spinhaler works

A

Capsule pierced by 2 metal needles
Inhalation = air flows = turbulence flow as rotor rotates
Powder dispersed to capsule wall + out into inspired air
Through perforations

38
Q

What does the HandiHaler contain?

A

tiotropium bromide
Unit-dose

39
Q

Describe Accuhaler

A

Multi-dose

40
Q

Describe the dose in Accuhaler

A

Drug preloaded = 60 doses
Each dose packed separately = exposed to ambient conditions

41
Q

What is problem to Accuhaler?

A

Insensitivity to humidity

42
Q

Describe how the Turbohaler (Symbicort) works

A

Drug flows on rotating disc unit
Excess removed by scarpers

43
Q

Describe the doses of Turbohaler (Symbicort)

A

200 doses of undiluted, loosley aggregated micronized drug

44
Q

What is not needed in the Turbohaler (Symbicort)?

A

No carrier
No individual dose loading

45
Q

What does the Turbohaler (Symbicort) require?

A

High inspiratory effort due to high internal resistance

46
Q

What is the problem with Turbohaler (Symbicort)?

A

More sensitive to humidity

47
Q

Because the Turbohaler (Symbicort) requires high inspiratory effort what does this mean?

A

May not be suitable for kids or elderly

48
Q

What are breath-assisted devices designed to do?

A

Reduce or eliminate reliance on patient’s inhalation effort to disperse the drug

49
Q

When are breath-assisted devices useful?

A

Patients who can only achieve low inspiratory flow rates

50
Q

What is an example of breath-assisted devices?

A

Spiros

51
Q

What was Spiros?
DISCONTINUED

A

Effort-assisted device using a battery-powered impeller to deaggregate + aerosolise the drug powder

S2 Case 3 - asthma & COPD (25 decks)

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