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AAI Pharmaceutics > Aerosols - Delivery Systems And Formulation For Inhalation 2 > Flashcards

Aerosols - Delivery Systems And Formulation For Inhalation 2 Flashcards

1
Q

What is an aerosol?

A

Dispersion of solid particles or liquid droplets in a gas

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2
Q

What three times of inhalers are there?

A

Nebulisers
Pressurised metered dose inhalers
Dry powder inhalers

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3
Q

Which is the most widely used inhaler and why?

A

PMDI - most convenient

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4
Q

What is a nebuliser?

A

Aqueous drug solution / suspension aerolised into droplets - energy provided by compressed air or ultrasound

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5
Q

What is a pMDI?

How is compliance improved by pMDI?

A

Pressurised metered dose inhaler
Drug formulated in a liquefied gas under pressure
Aerosol formed by evaporation of gas at atmospheric pressure
More compliance because works same from device to device and fewer steps

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6
Q

What is a DPI?

A

Dry powder inhaler
Drugs normally with other solid excipients in dry powder state
Aerosolisation by patient

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7
Q

What are the two types of nebuliser?

A 
Jet Nebuliser (or atomiser)
Ultrasonic Nebuliser
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8
Q

How does a Jet Nebuliser work?

A

Air from compressor forced through narrow hole to give high velocity air stream
High velocity air breaks drug solution / suspension into droplets for inhalation
Baffles are used to remove larger particles

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9
Q

How does an Ultrasonic Nebuliser work?

A

Piezoelectric crystal emits high frequency signal
Breaks drug solution / suspension into droplets for inhalation
Lighter and quieter than a jet nebuliser

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10
Q

What is a drawback of Ultrasound Nebuliser?

A

Some drugs are degraded by the ultrasound

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11
Q

How is a nebuliser used?

A

Patient breathes normally into the face mask or mouth piece

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12
Q

Advantages of a nebuliser

A

Aqueous drug solutions used (very simple for soluble drugs)
No hand lung coordination needed so good for elderly and children
No controlled inhalation manoeuvre required
Large doses of drug and mixtures not normally available can be given
Relatively low cost
Visible mist can reassure the patient

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13
Q

Disadvantages of nebulisers

A

Not fully portable
Equipment not fully regulated yet
Lengthy nebulisation time
Low efficiency (much of solution is wasted)
Solution concentrates as water evaporates
Insoluble drugs require solubilisation
Some suspensions are difficult to nebulise
Susceptible to microbiological contamination

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14
Q

Criteria for a pMDI container

A 
Withstand high pressure 
Robust 
Light in weight 
Inert 
Made of aluminium or stainless steel (steel better for higher pressures)
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15
Q

What is a pMDI metering valve?

A

Ensures accurate and reproducible volume of drug formulation is delivered
Delivered from continuous spray valves
20-100 microlitres

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16
Q

Properties of a pMDI propellant ?

A

Liquid under pressure of 3-5 atmospheres
Gas at atmospheric pressure and ambient temperature
It’s vapour pressure must stay constant - dose uniformity
Non flammable and non toxic
Chemically inert

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17
Q

Discuss CFC propellant

A

Ozone depleting
Banned
Responsible for the cold - freon effect

18
Q

Discuss hydrofluoroalkanes as propellant

A

Drugs needed to be reforms later due to different properties of HFA compared to CFC
New valve materials developed

19
Q

If a drug is soluble in propellant how is it formulated into a pMDI?

A

Solubilised in propellant

Ethanol might be added as a co-solvent

20
Q

If a drug is insoluble in propellant how is it formulated into a pMDI?

A

Micronised drug particles are suspended in propellant
Surfactants added to increase suspension stability
Most common pMDI formulation

21
Q

What is needed to form an aerosol?

A

Source of energy

22
Q

What is the main concern for each dose from a pMDI?

A

Each dose is correct and the volume of suspension is homogenous

23
Q

Why are surfactants added to the formulation of a pMDI?

A

Improve stability / homogeneity of the suspension

Aid the formulation of a flocculated suspension (easily redispersible)

24
Q

What are the four main problems facing the suspension in a pMDI inhaler?

A

Sedimentation (non-homogeneity)
Flocculation (reversible aggregation)
Caking - difficult to redisperse
Particle size growth by Otswald ripening (deposition in the lungs reduced)

25
Q

What are the ideal criteria for suspension of pMDI?

A

Slow flocculation
Slow sedimentation
Easy redisperse
I.e partially flocculated suspension

26
Q

What other add on excipients can be used in pMDI?

A 
Flavours 
Sweeteners
Lubricants 
Density modifiers 
Antioxidants
27
Q

How do spacer devices help with inhalation of pMDI?

A

Increase lung deposition

  • delay between actuation and inhalation
  • decrease the velocity of the spray
  • more time for propellant to evaporate
28
Q

Why is the dose inhaled by a patient reduced when using a spacer and pMDI?

A

Deposition in the device due to electrostatic charges causing droplets to stick to the chamber

29
Q

pMDI advantages

A

Compact portable robust convenient
Multi dose
Short treatment time
Consistent formation / operation for all pMDIs
Good dose content uniformity
Good protection against moisture and pathogens
Inexpensive

30
Q

pMDI disadvantages

A

Usually no breathe actuation
Low lung deposition
No dose counter (to record used)
Only low doses can be delivered (

31
Q

What is a Dry a Powder Inhaler?

A

Dry powder, no solvent is involved

32
Q

Main components of a DPI

A

Drug powder or blend with excipients
Drug reservoir or pre-metered doses (cartridge, blister, capsules)
Body of the device
Cap to protect powder from dust / moisture

33
Q

How is patients inspiratory flow used in a DPI?

A

Fluidise the static powder blend

De-aggregate particle agglomerates into inhalable particles

34
Q

Why is particle size problematic in DPIs?

How is this solved?

A

Particles must be small (

35
Q

Three types of DPI

A

Unit dose devices
Multiple unit dose devices
Reservoir devices

36
Q

Single dose inhalers DPI

A

Drug and excipients capsule inserted into device by patient
Capsule broken by movement of some part of the inhaler
Patients inhale the drug and excipients powder blend
-not convenient to use

37
Q

Multi use dose MDI

A

Drug and excipients in blister packs
Incorporates a dose counter
Blister pierced by moving mechanism in the device / ratchet
-relatively convenient

38
Q

Multi dose reservoir DPI (like mams)

A

Drug dispensed into the chamber by patient action eg twisting
Most are disposable one use only
Powder equivalent of a pMDI

39
Q

DPI advantages

A 
Compact, portable, convenient 
Breath-actuated 
Higher doses than pMDI
Dose counter 
Formulation easier 
Dry state --> better stability 
Environmentally friendly (no propellant)
40
Q

DPI disadvantages

A 
Breath-actuated 
Can not be used by young children as inspiration rate too slow to trigger a DPI 
Different designs
Affected by ambient humidity 
Expensive

AAI Pharmaceutics (2 decks)

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