Colloids 6 W4 Flashcards
Aerosol ?
liquid or solid dispersed phase in a continuous phase of a gas (air)
Formulation development allows…..
a drug to be delivered most effectively for its’ particular purpose.
Nebulised adv and disadv
√ :
- Maximal effect after 15-30 mins
- lasts 3-4 h
- no patient education required
- no first pass metabolism
X :
- larger particles and hence dose required
- higher incidence of systemic side effects
Inhalers adv and disadv
√ :
- as effective as nebulised salbutamol
- lower dose
- fewer side effects,
- no first pass metabolism
X :
- patient education required
IV adv and disadv
√:
- no first pass metabolism, -potentially efficacious in severe asthma
X:
- requires IV access
- more systemic side effects, - expensive
Oral adv and disadv
√:
- longer half-life
- easier administration in disabled/very young patients
X:
- Steady-state plasma concs reached after 3 days, 50% first pass metabolism
- larger dose, higher side effect profile
What does particle sizer determine
How far into the lung a particle can penetrate is heavily determined by particle size
Stokes number
is a dimensionless number used in fluid dynamics and aerosol science to describe the behavior of particles suspended in a fluid flow.
Stk = pd^2vflow / 18uR
Stk = properties propelling the particle (density, size, velocity) / properties resisting the particle (medium viscosity and dimension – here, airway diameter)
How does stokes number change
As a particle is inhaled and passed through different parts of the lungs, its stokes number os going to change because he airways it’s travelling through will become more constrictive
High stokes number and its deposition mechanism
> 10
particle has high inertia and will impact on obstacles rather than flow round them
Impaction
Moderate stokes number and its deposition mechanism
1-10
particle is still large and dense enough to be subject to gravitational settling in the lung
Gravitational settling
(Moe likely to floe with direction of air flow but still dense enough for sedmentatio in lung )
Low stokes number and its deposition mechanism
<1
Particle is buffeted by the medium and diffuses with Brownian motion
Brownian diffusion
(Carry on moving with airflo and doesnt fall out of airflow, no sediment . Diffuse with brownian when airflow is too low)
Size of particles that are efficiently deposited and absorbed
Only in the range of 1-5um
This is the respirable fraction
Respirable fraction
refers to the portion of airborne particles small enough to penetrate deep into the lungs, specifically reaching the alveolar region, where gas exchange occurs.
%of particles between 1-5u
(% under 5um - % under 1um)
Where do larger and smaller particles hit
Larger particles hit the mouth and upper airways; smaller particles stay buoyant and are breathed out again before settling.
