Pressurised Metered Dose Inhalers + Nebulisers

Question 1

What must the drug be in pMDI?

Answer 1

Dissolved/suspended in non-polar volatile propellant

Question 2

Describe the delivery of the drug in pMDI

Answer 2

Drug in solution or suspension in pressurised canister
Actuation of metering valve - pre-determined dose released
Vol expansion of formulation
Enters airways as fine spray of droplets

Question 3

What does deposition depend on?

Answer 3

Inspiratory flow + separation

Question 4

What are the containers?

Answer 4

Aluminium canisters
10-30ml
Inert

Question 5

What is the vol of medicine in the metering valve component?

Answer 5

25-100 microL

Question 6

Describe the metering valve component

Answer 6

Inverted position
Valve stem fits into actuator

Question 7

Describe what happens with metering valve component

Answer 7

Depression of valve stem = contents discharged
After actuation = refills with liquid

Question 8

What must happen to pMDI?

Answer 8

Needs to be primed
= pressed multiple times

Question 9

Describe the actuator component

Answer 9

Polyethylene or polypropylene

Question 10

What do the dimensions of the orifice in the actuator determine?

Answer 10

Shape, speed + emitted aerosol

Question 11

Describe the propellants component

Answer 11

Liquefied gases
Liquid under high pressure in cannister

Question 12

What are the propellants that are used?

Answer 12

Hydrofluroalkanes

Question 13

What are the problems with propellants?

Answer 13

Poor solvents

Question 14

What can pMDIs be?

Answer 14

Solution or suspension

Question 15

What should the particle size be?

Answer 15

Solution or suspension

Question 16

Why does it say to “breathe in slowly + deeply”?

Answer 16

Minimise inertial impaction

Question 17

Why does it say to “hold your breath for as long as possible”?

Answer 17

Allow for drug particle to follow air into lungs

Question 18

Why does it say, “do not breathe into the inhaler”?

Answer 18

Block the valve

Question 19

Why does it say to “shake”?

Answer 19

If the formulation is a suspension

Question 20

What do spacers reduce?

Answer 20

Aerosol velocity, allowing for more time to inhale the drug

Question 21

What must you make sure when dispensing a spacer?

Answer 21

Compatible with pMDI mouthpiece

Question 22

What may be attached to a spacer for young patients?

Answer 22

Mask

Question 23

What is the drug in nebuliser?

Answer 23

Dissolved/suspended in polar solvent (usually H2O) + aerosolised

Question 24

How does nebuliser deliver it to the lungs?

Answer 24

Drug in solution/suspension added to nebuliser drug reservoir
Nebuliser connected to power source
Drug solution aerosolised
Enters airways as fine spray of droplets

Question 25

What is dissolution dependent on?

Answer 25

Droplet density, charge + size

Question 26

What is absorption dependent on?

Answer 26

Patient inhalation pattern + airways

Question 27

What are the different types of nebulisers?

Answer 27

Jet nebulisers Ultrasonic nebulisers Vibrating mesh nebulisers

Question 28

What do nebulisers consist of?

Answer 28

Compressor supplying compressed air Nebulising chamber containing nebulised drug Mouthpiece or face mask

Question 29

What are jet nebulisers driven by?

Answer 29

Driven by compressed air

Question 30

What does the rate of air flow determine in jet nebulisers?

Answer 30

Droplet size + rate of drug delivery

Question 31

Describe the Bernoulli principle + Venturi effect

Answer 31

Compressed gas passes through capillary tube = increases air velocity = low pressure zone around nozzle (V) = formulation to rise in liquid reservoir (B)

Question 32

What are the issues with jet nebulisers?

Answer 32

Quite noisy = affect patient acceptability Continuous operation = significant amount of drug lost

Question 33

Describe how ultrasonic nebulisers work

Answer 33

Sound wave created from vibration of piezoelectric crystals at high frequency = creates crests that break liquid particles into small droplets

Question 34

What do ultrasonic nebulisers require?

Answer 34

Power source

Question 35

How do vibrating mesh nebulisers work?

Answer 35

Passing liquid drug through vibrating mesh

Question 36

What droplet size do vibrating mesh nebulisers produce + what is it ideal for?

Answer 36

1-5 micrometres Ideal for deep lung deposition

Question 37

What are the advantages of vibrating mesh nebulisers?

Answer 37

Quieter + more portable

Question 38

Describe formulating nebuliser fluids

Answer 38

Formulated in H2O Surfactants added = suspension Iso-osmotic fluid = pH3-10

Question 39

What isn't often added to nebuliser fluids + why?

Answer 39

Antioxidants + preservatives = cause bronchospasm

Question 40

Why must it be pH 3-10?

Answer 40

Avoid bronchoconstriction

Question 41

What is poorly delivered from ultrasonic nebulisers?

Answer 41

Suspensions

Question 42

Why may the fluid in jet nebuliser drop in temperature?

Answer 42

Due to evaporation of solvent during nebulisation

Question 43

What may happen if the fluid drops in temperature?

Answer 43

Drug solubility may be reduced Affect asthmatic patients who suffer from bronchoconstriction