pulmonary dd – Pmdi 16 Questions with Answers
why is inhalation a good drug delivery route ? - CORRECT ANSWER - large surface area
- good blood
... [Show More] supply
- thin diffusive layer
- lower enzyme activity
- non-invasive
- local & systemic delivery
what are some of he barriers that have to be overcome for respiratory drug inhalation ? - CORRECT ANSWER mechanical:
> physical stability of the aerosols
> impaction (deposition)
> device efficacy
chemical:
> drug degradation
imuno & clearance:
> mucociliary clearance
> macrophages
behavioural
> adherence
> poor technique
what is an aerosol ? - CORRECT ANSWER two-phase system of solid particles/liquid droplets dispersed in air/gaseous phase
what are the particle depositions that have to be overcome in respiratory delivery ? - CORRECT ANSWER inertial impaction:
> large particles hit the back of the throat
gravitational sedimentation:
> particles settling under gravity
brownian motion:
> particles constantly moving and colliding with each other so they cannot deposit
what is the ideal particle size for an aerosol molecule ? - CORRECT ANSWER 1-5um
what is aerodynamic diameter (da)? - CORRECT ANSWER physical diameter of a sphere which settles through air with a velocity equal to the particle
what does MMAD stand for ? - CORRECT ANSWER means median aerodynamic diameter
how does airway humidity effect the particles ? - CORRECT ANSWER - water condenses onto particle surface
> water insoluble materials: thin film of water
> water soluble materials: increased size & higher deposition
what is a pMDI ? - CORRECT ANSWER pressurised metered dose inhaler:
- drug is dissolved or suspended in a liquid propellant & kept in a pressurised canister with a metering valve
parts:
> canister
> metering valve
> actuator
> mouth piece
what is a propellant ? - CORRECT ANSWER - volatile liquid (has to evaporate off leaving behind drug only) propellant which forms a gas when released into atmospheric pressure
examples:
> chlorofluorocarbons (CFCs): now banned
> hydrofluoroalkanes (HFAs): now used
how is drug formulated in a pMDI ? - CORRECT ANSWER suspended or dissolved
suspension:
- more common
- can aggregate (must shake before use)
dissolved/solution:
- requires high solubility in propellant
- hard to form
what are each of the part used for in a pMDI ? - CORRECT ANSWER canister:
> usually aluminium (inert)
> protects formulation
actuator:
> nozzle: determines particle size
> mouthpiece: influences efficacy of use
metering chamber & valve:
> releases an accurate & reproducible dose to patient
> hold defined volume of formulation
why are spacers used ? - CORRECT ANSWER pMDI & spacers
- compensates for poor techniques
- allows for more time for propellant to evaporate off
- increases lung deposition
- reduces initial droplet velocity & large droplets removed by impaction
- non cold freon effect (forceful cold blast of propellant on back of thought)
what are some disadvantage of spacers ? - CORRECT ANSWER - bulky
- need to be washed
- replaced every 6-12 months
what are some alternatives to spacers ? - CORRECT ANSWER collapsible holding chamber:
adv
- collapsible
- portable
- durable
dis
- difficult to use
- bad seal for drug delivery
what are the types of pMDI ? - CORRECT ANSWER breath actuated pMDI:
- automatically release of spray when breath in
- reduces need for coordination
connected pMDI:
- combines pMDI with sensor technology with propeller electronics (phone) [Show Less]