Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Pharmacy Stage 2 > Pressurised Metered Dose Inhalers and Nebulisers > Flashcards

Pressurised Metered Dose Inhalers and Nebulisers Flashcards

1
Q

what is a pMDI?

A

a solid drug dissolved/suspended in a non-polar volatile propellant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

how does a pMDI deliver drugs to the lungs?

A
  1. drug in solution or suspension in pressurised canister
  2. actuation of metering valve so pre-determined dose releases
  3. volume expansion of formulation so droplet released
  4. enters airways as fine spray droplets
  5. deposition depends on inspiratory flow and separation
  6. dissolution
  7. absorption into lungs
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are pMDI containers made from?

A

aluminium or tin-plated steel (so they’re inert)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is used to control the dose of drug being released?

A

the metering valve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the actuator of a pMDI made of?

A

polyethylene or polypropylene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is the role of the actuator?

A

determines shape and speed of emitted aerosol cloud

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are propellants and give examples of them?

A

they’re liquefied gases e.g. Chlorofluorocarbons (CFCs) and Hydrofluoroalkanes (HFA’s) (liquefied due to high pressure in canister)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

why have HFA’a replaced CFCs as propellants?

A

as CFCs cause ozone depletion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is the role of propellants?

A

provide required pressure to atomise the drug formulation into micron-scaled droplets as upon actuation the propellant expands and vaporises under ambient conditions with associated dispensing of the metred dose as an aerosol spray.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what excipients are included in a pMDI?

A

co-solvent (ethanol)
surfactants (tween80)
suspending agents (prevents caking of suspension)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are the 5 key components of a pMDI?

A
  1. container
  2. metering valve
  3. actuator
  4. propellant
  5. excipients
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what 6 factors must you consider when formulating a pMDI?

A
  1. drug solubility in propellant
  2. propellant density
  3. particle size
  4. valve clogging
  5. stability
  6. moisture content
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what two key conditions are required for filling pMDI canisters?

A
  1. cold (so fill at low temp. drug formulation pre-chilled at -60 degrees)
  2. high pressure (fill canister at elevated pressure passing the vapour through the valve)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

explain how aerosol generation pMDIs work?

A
  1. patient presses down on can which opens the channel b/w the metering chamber and atmosphere
  2. propellants boil in expansion chamber
  3. propellant droplet form at actuator nozzle ready to disperse at an initial size of 20-30uM and speed of 30m/s.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what pMDI’s are used in the clinic?

A
  1. SABA (salbutamol)
  2. SAMA (ipratropium bromide)
  3. LABA (salmeterol)
  4. LAMA (tiotropium)
  5. ICS (beclometasone, fluticasone)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are the pros and cons of pMDIs?

A

pros:

  1. relatively low cost
  2. reproducible dose delivered from device
  3. convenient many doses in one canister
  4. inert environment protects drug from oxidation and contamination
    cons:
  5. patient use errors
  6. inefficient drug delivery (more drug loss)
17
Q

what is used to overcome breath-hand co-ordination difficulties when using pMDIs?

A
  • Breath-activated pMDIs (inhaling triggers aerosol activation)
  • Inhalation aids (i.e. spacers. This reduces aerosol velocity and allows more time for evaporation of propellant.)
18
Q

how often do you:

a) wash your spacer?
b) replace your spacer?

A

a) once a week with warm soapy water and leave to air dry

b) once every 6-12 months

19
Q

which of the two require more co-ordination, DPI or pMDI?

A

pMDIs

20
Q

which of the two depends more on patient’s IFR, DPI or pMDI?

A

DPI

21
Q

why do pMDIs have more stability issues than DPIs?

A

because the pMDI is a 2 phase system whilst DPIs are single phase systems

22
Q

what are nebulisers?

A

drugs dissolved/suspended in polar solvents and aerosolised. polar solvent is usually water

23
Q

how does a nebuliser deliver drug to the lungs?

A
  1. drug in solution added to nebuliser drug reservoir
  2. nebuliser connected to power source
  3. drug solution aerosolised
  4. enters the airways as a fine spray of droplets
  5. deposition independent of IFR
  6. dissolution
  7. absorption into lungs
24
Q

three ways, through which, drugs are delivered, to the lungs, from a nebuliser?

A
  1. mouthpiece
  2. face mask (but not for steroids)
  3. ventilator
25
Q

why is the pH of the drug solution buffered ?

A

to match the pH of the lungs

26
Q

why are salts added to the drug solution?

A

to match the tonicity

27
Q

why are surfactants added to the drug?

A

to increase solubility

28
Q

what diluent is included in the nebuliser formulation?

A

sodium chloride

29
Q

how do you administer oxygen to COPD patients requiring oxygen and jet nebulisation?

A

-uses air to administer via a nasal cannula

30
Q

what is the Bernoulli and Venturi effect?

A
  1. compressed gases move through narrow capillary tube
  2. increased air velocity creates low pressure zone around the nozzle (venture effect)
  3. fall in pressure causes the formulation to rise from liquid reservoir (Bernoulli effect)
  4. large droplets impact on baffles ad break into smaller droplets or remain in device.
31
Q

downside to using a jet nebuliser?

A
  1. compressors are quite noisy

2. continuous operation means large proportion of emitted aerosol is released into the air and not inhaled

32
Q

how do ultrasonic nebulisers work?

A
  1. sound waves created from vibration of piezoelectric crystals at high frequency. this requires a power source. no gas flow required.
  2. this creates crests that break the liquid particles into small droplets to be inhaled
  3. not suitable for all meds and suspensions though
33
Q

How does a passive Vibrating Mesh Nebuliser (VMN) work?

A
  • piezoelectric crystal generates vibration from electrical force to transducer horn that’s in contact with the formulation
  • vibration creates waves in nebuliser reservoir that travel towards a perforated plate in front of the horn
  • aerosols are created when formulation flows through the membrane and drops detach
34
Q

How does an active VMN work?

A
  • dome-shaped membrane directly connected to vibrating piezoelectric element
  • following application of electric current, membrane vibrates up and down causing formulation to extrude through the mesh as droplets
35
Q

SUMMARY!!

A

Look at table on side 40!

Pharmacy Stage 2 (85 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions