METERED DOSE INHALERS 2

Question 1

what are the different materials used in aerosol containers?

Answer 1

aluminium
tin-plated
glass
plastic

Question 2

what are the 2 types of fillings of pdmis?

Answer 2

cold filling and pressure filling

Question 3

what are the 4 components of MDI?

Answer 3

propellant/ surfactant/ drug/ co-solvent

Question 4

what are the differences between cold and pressure filling?

Answer 4

cold filling- contents & propellant are cooled sufficiently so volatilisation is minimised
pressure filling-the contents/propellant kept under pressure, no refrigeration needed.

Question 5

what is done at both the end of cool and pressuried filling?

Answer 5

leak test

Question 6

what is the aerodynamic diamater?

Answer 6

median size divides frequency distribution in half
- it is the equivilant diameter
aerodynamic diameter is defined as the diameter of a sphere of unit density (1 g/ml) which has the same terminal settling velocity as the particle in question

Question 7

how do you calculate the aerodynamic diameter?

Answer 7

• Stokes diameter x square root of particle density- estimate

Question 8

is a visual indication and indication of the aerodynamic diameter?

Answer 8

no-some particles appear to be visually similar can have different aerodynamic diameters

Question 9

what is the cascade impactor used for?

Answer 9

used to characterize aerodynamic particle size

Question 10

how does the cascade impactor work?

Answer 10

particles sampled through series of stacked stages
•each stage has multiple orifices with sequentially smaller diameters (increases particle velocity)
•ambient air enters bent pipe throat and cascades through the succeeding orifice stages with successively higher orifice velocities from Stage 0 to Stage 7
•smaller aerodynamic sized particles are inertiallyimpacted onto pre-calibrated collection plates
•sub-micron particles (<1.0μm) collected by filtration (Final Filter). •air is drawn through the Cascade Impactorusing vacuum pump at 28.3 litres/min for pMDI
•pre and post weigh the 81mm plates located below each orifice stage or rinse plates and assay for drug content

Question 11

what is probability paper?

Answer 11

where we graph our results on- usually straight line- if not log it to get straight line

Question 12

what are the two parameters in the probability paper?

Answer 12

wo parameters -the mass median aerodynamic diameter (MMAD) and the geometric standard deviation (GSD). The probability plot yields a straight line on log probability paper. Determine the apparent MMAD and GSD from this linear plot