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Mpharm Y2S1 > Inhalation Formulations > Flashcards

Inhalation Formulations Flashcards

1
Q

What will particles larger than 10µm do when inhaled?

A

Hit the back of the throat and be removed

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2
Q

What will particles between 1- 5µm do when inhaled?

A

Sediment in bronchioles, desired effect

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3
Q

What will particles smaller than 1µm do when inhaled?

A

Brownian diffusion to aveoli and sediment there

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4
Q

What are four types of aerosol generating devices?

A
  • Pressurised metered- dose inhalers
  • Dry powder inhalers (DPIs)
  • Nebulisers
  • Novel delivery services
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5
Q

What is in the formulation of an MDI?

A

Drug
HFA propellant
Surfactant
Co- solvent/ excipient

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6
Q

What is the canister of a MDI made up of and why?

A

Aluminium, glass, plastic coated all 10-30ml
All inert

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7
Q

Why is a propellant/ solvent added to a MDI?

A

To dissolve the drug

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8
Q

What is the mechanism of how an MDI works?

A

In the canister its originally a gas
Its liquified to increase temp or decrease pressure as when the nozzle is pressed the pressure decreases so can expand and become an aerosol

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9
Q

What are the features of a suspension formulation in an MDI?

A

Micronised drug particle suspended in liquified propellant
Chemically stable
Physical stability:
- sedimentation/ creaming for larger than 1µm particles
- drug desposition
- Particle growth- Ostwald ripening

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10
Q

What are the features of a solution formulation in an MDI?

A

Drug dissolved in liquified propellant
Excellent dose reproduction
‘Fine spray’= high throat deposition
Limited to high potency, low dose drugs
Prone to chemical degradation

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11
Q

Name two types of propellents and which ones are presently used:

A

CFC’s - chlorofluorocarbons
HFC’s - hydrofluorocarbons- present

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12
Q

Why are CFC’s no longer used?

A

Due to photolysing which forms radicals and attacks the ozone layer

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13
Q

What are benefits and disadvantages of HFC’s?

A

+ Non flammable
+ Produce slower velocity spray and smaller droplets
+ Miscible with water and alcohol
- Not good solvent for surfacant

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14
Q

How are HFA’s numbered?

A

1st digit: number of C atoms- 1
2nd digit: number of H atoms +1
3rd digit: number of fluorine atoms

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15
Q

What are the benefits of spacers with MDI?

A

More time with spacer as providing extra distance between aerosol and patients mouth
So more time to co-ordinate the actuation and inhalation
Collects larger particles inside so none in mouth

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16
Q

What are new MDIs and why are they good?

A

Respimat soft mist inhaler
Solution
Slow velocity mist of fine particles
Velocity 0.8 m/s
More time for co-ordination

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17
Q

What are the function of co-solvents in MDIs?

A

Increase solubility
Wetting agent- improve suspension behaviour
Valve function and reduced friction
Ethanol and PEG1000 are co- solvents

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18
Q

What is a dry powder inhaler, DPI?

A

Breath activated device that aerosolises a set dose of micronised drug in the solid state, a strip of blisters contain drug

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19
Q

What is the formulation of a DPI?

A

API < 5µm
API/ carrier (lactose monohydrate)

20
Q

What are four types of commercial APIs?

A

Aerolizer
Handihaler
Accuhaler
Turbuhaler

21
Q

What are the benefits of using a DPI over an MDI?

A

Provides more lung deposition than an MDI as in MDI, most of inhaled dose was deposited in the oropharynx and stomach

22
Q

What are 3 types of formulation in DPIs?

A
  • Pre formulated small particles
  • Loose agglomerates of drugs and excipient particles
  • Drug particles carrier (lactose) blend
23
Q

What are weak interactions in drug particle carrier blend of DPIs?

A

Poor flow ability so poor delivered dose consistency
Enhanced aerosolisation performace
Fine lactose

24
Q

What is a good formulation in DPIs?

A

Sophisticated balance in particle- particle interactions, good flow, good aerolisation, come off lactose after inhalation

25
Q

What are strong interactions in drug particle carrier blend of DPIs?

A

Better flow ability so better delivered dose consistency
Comprimised aerosolization performance
Larger lactose

26
Q

Describe what are single dose DPIs and how are they used?

A

Spinhalers
Each dose contains a hard gelatin capsule
Put capsule inside, pierce and inhaling causes powder to come out
Requires cleaning afterwards so not very practical

27
Q

Describe what are multi 8 dose DPIs and how are they used?

A

Diskhaler
Blister packaged powder
Preloaded in foil
The blister is broken by sliding the lever to expose powder
8 doses, has a counter/ plastic needle/ cleansing brush

28
Q

Describe what are multidose DPIs and how are they used?

A

Accuhaler and Turbohaler
200 doses
No carrier
Blister is pierced by pin and access to powder by breathing

29
Q

What are advantages of DPIs?

A
  • No co-ordination required
  • Good for children, elderly, arthritic
  • Good stability profile for sensitive drugs (as they’re a powder)
  • Low velocity at mouth piece
    Potential for high doses
30
Q

What are the general principles of nebulisers?

A

Drug is dissolved in solution, aqueous based
Buffer vehicles to match pH in lung (6.5), high pH can cause bronchospasm
Salts for isotonicity, hypo/ hyper can cause bronchospasms, surfactants for solubility
Stabilisers required to control droplet viscosity
Chemical preservatives not recommend, may cause bronchospasm

31
Q

What are two marketed nebulisers:

A

TOBI Tobramycin inhalation
Solution Ventolin inhalation

32
Q

What are Air Jet Nebulisers?

A

Compressed air fed through Venturi nozzle
Area of negative pressure is generated at the opening of the nozzle
Small amounts emilled as filaments, to form droplets and pulled up by inhalation

33
Q

What is a Venturi nozzle:

A

Thin pipe, 0.3- 0.7mm diameter

34
Q

What are the disadvantages of air jet nebulisers:

A

Much wastage, modern designs try to overcome this by adding valves

35
Q

What are ultrasonic nebulisers?

A

Transducer which has a high freq vibrating surface which vibrates the liquid which generates droplets, piezo- electric crystals

36
Q

What is a beneficial structure to ultrasonic nebulisers?

A

They have a baffle system which pushes larger particle droplets back down in the nebuliser

37
Q

How do mesh nebulisers work?

A

Passing liquid though a vibrating mesh with multiple holes using vibrating piezoelectric crystals
Generation of aerosol with high particle fraction

38
Q

What does it mean that mesh nebulisers have an AAD system?

A

Adaptive Aerosol Delivery System
Analyse patients breathing pattern and emit only during exhalation

39
Q

What effect does viscosity have on the air jet nebuliser formulation?

A

Lower viscosity solutions are easier to atomise, therefore size of droplets inversely proportional to viscosity

40
Q

What effect does surface tension have on the air jet nebuliser formulation?

A

Overall affects complex but lower ST solutions are easier to atomise, therefore size of droplets inversely proportional to ST

41
Q

What effect does temperature of solution have on the air jet nebuliser formulation?

A

Solution temp decrease during nebulisation by 10–15°C
Temp decrease may be felt during inhalation
May cause precipitation of drug by affecting solubility
May affect ST and viscosity

42
Q

What effect does temperature have on the ultrasonic nebuliser formulation?

A

Increases temp during nebulisation by 10–15°
Can be felt during inhalation
Drug denaturation

43
Q

How long does a nebuliser work for?

A

Generally until dryness
Airflow cause a sputtering
Dead volume approximately 1ml- means can’t be nebulised

44
Q

Are advantages of nebulisers clinically?

A
  • Breathing coordination not important
  • Good for patients who can’t control manual handling and breathing
  • used when dose is too large for DPIs and MDIs
45
Q

What is the disadvantage of nebulisers clinically?

A

May lose large quantities of aerosol during expiration

Mpharm Y2S1 (12 decks)

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