inhaled medicine
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what is the physical purpose of airways?
to humidify and heat the air inhaled remove particles in air inhaled to clear deposited particles into the GI tract particles shouldn’t reach the alveoli
why is taking an inhaler delivered to the lung?
via respiratory tract for local and systemic effect ‘rapid onset of action’ comfortable to take the doses are smaller than oral doses so less systemic and GI adverse tract
how are barriers for delivery and to penetrate airways overcome?
drugs delivered int eh form of aerosol
what is aerosol?
suspension of liquid or solid particles in gas
what makes an aerosol particle effective?
deposits int he appropriate region in the lung overcomes physiological barriers right quantity of drug
what is stoke’s law equation?
don’t need to remember equation: slide 7
relationship between viscosity and velocity in strokes law?
as viscosity goes up the velocity goes down
what is the equation of aerodynamic diameter?
don’t need to remember this: slide 7
what size do particles need to be?
particles need to be less than 10 microns to get into lungs
what is the defintion of the respirable fraction of an inhaled medicine?
‘percentage present in aerosol particles less than 5 micrometres so less likely to be deposited’
what devices can be used to stimulate inhalation process?
Anderson Cascade Impacter Next Generation Impinger
how does the NGI work?
7 stages calibrated to flow rate required powder is collected in cups size distribution is a prediction of site of deposition of drugs in the lungs
what are the three types of inhalers?
Nebulisers Pressurised metered dose inhalers (pMDI) Dry powder inhalers (DPI)
how does nebeulisers work?
aqueous drug with energy supplied by compressed air
how does pMDI work
liquified ga under pressure aerosol formed by evaporation of gas
how does the DPI work?
dry powder delivered no solvent deliveries a large dose compared to pMDI breath actuated drug in dry form more stable than drug in solvent
how is the dose in pMDI aquired?
when pMDI pressed down only liquid in metering chamber is released
why does an inhaler get shook before use?
because metering chamber needs to be filled to make sure no settling of particles and drug is distributed
when is a spacer device used?
with patients with poor coordination
what are the problems with DPI?
dose delivery and deposition depends on patients inspiratory flow rate particles less than 5 micrometres are needed to enter the lung but are cohesive moisture causes agglomeration
what are the solutions for issues with DPI?
spherical particles reduce aggregation protected form moisture drug blended with carrier particle that are larger particles so drug has to be separated before inhalation
what are the types of DPI?
unit dose devices multiple unit dose devices reservoir devices
what is the formulation of DPI?
ordered mix-carrier particles used to stop small particles form aggregating small particles have to be separated from carrier particles before inhalation drug is deposited in the lungs