Lecture 2

Question 1

Define pMDIs

Answer 1

Are compact pressurised aerosol dispensers

Question 2

How is the aerosol formed by the propellant?

Answer 2

Pressure converts gas to liquid, drug formulated in liquid, when pressure is released, the liquid propellant changes to a gas, leaves aerosol of particles

Question 3

What is the current pMDI propellant?

Answer 3

Hydrofluroalkanes (HFAs)

Question 4

How is the spray formed?

Answer 4

1) Patient presses the can which opens a channel between the metering chamber and the atmosphere
2) Propellants start to boil in an expansion chamber
3) Shearing forces produce ligaments
4) Propellant droplets form an actuator nozzle
5) Left with propellant and drug, but propellant quickly evaporates and you are just left with the drug suspected in the air

Question 5

Define rapid flocculation

Answer 5

Loose agglomerates - attractive forces pull the drug particles together

Question 6

Define bulk separation

Answer 6

Creaming or sedimentation, drug settles at bottom or floats at top

Question 7

Define irreversible aggregation

Answer 7

‘Ostwald ripening’ (smaller particles dissolve and deposit on larger particles), caking

Question 8

Define crystal structure instability

Answer 8

polymorphic interconversion (transition from one solid form to a more stable one)

Question 9

What is the role of the excipient?

Answer 9

ensure physical stability of suspension

Question 10

Benefits of surfactants

Answer 10

Prevents particles from sticking together and keeps particles suspended in there

Question 11

Give examples of commonly used surfactants

Answer 11

Oleic Acid, Magnesium Stearate, PEG, PVP

Question 12

Benefits of co-solvents

Answer 12

Help dissolve the drug in the propellant needs to be stable once dissolved

Question 13

Example of a co-solvent

Answer 13

ethanol

Question 14

What are the issues with co-solvents?

Answer 14

could cause corrosion of aluminium canisters and lowers internal propellant pressure

Question 15

Benefits of space devices

Answer 15

Collects drug in the chamber - gives time for patient to slow down, no need for coordination

Question 16

What are breath-actuated inhalers?

Answer 16

The mechanism automatically activates pMDI when the patient inhales at a fast enough rate, removes need to press canister

Question 17

Give examples of a breath-actuated inhaler

Answer 17

Autoinhaler, Easi-breathe

Question 18

Describe a Haleraid

Answer 18

helps patients who cannot press top of canister, recently discontinued

Question 19

What are the concerns with pMDI?

Answer 19

HFAs are powerful greenhouse gases