Pharmaceutics Flashcards
Benefits of pulmonary route?
Avoid oral problems
No first pass metabolism
Rapid absorption
Macromolecules
Disadvantages of pulmonary route?
Disease state
Device/drug formulation
Patient anatomy
What does an aerosol system comprise of?
Particles (solid or liquid)
Gas (usually air)
Main options for achieving an aerosol?
Drug in propellant cloud (pMDI)
Powder dispersed in air (DPI)
Fine droplets in air (nebulisers)
Where should aerosol particles be deposited?
Must penetrate to smaller airways to be effective
Why is particle size important in aerosols?
> 10mcm deposit in oropharynx
5mcm deposit in central airways
<5mcm deposit in peripheral airways
Three mechanisms for how particles may deposit in the lungs?
Inertial impaction
Sedimentation
Diffusion
What is inertial impaction in regard to lung deposition?
Where particles impact parts of the respiratory tract. Less likely with smaller particles. Less likely with slow velocity.
What is sedementation in regard to lung deposition?
Gravity. Main source of deposition of small particles in peripheral airways. Holding breath allows time for sedimentation
What is diffusion in regard to lung deposition?
Random movement. For very small particles. In periphery of lung. Negligible importance
How are inhaled particles cleared?
Ciliated airways
Macrophages
Dissolution
Why is are patients advised to use inhalers whilst upright?
To keep the airways clear to reduce impaction
Why are patients advised to breathe in slowly when using an MDI?
To lower velocity of particles to reduce impaction
Why are patients advised to breathe in fast when using an DPI?
Need to disaggregate the particles and no pressure in the product itself
Purpose of surfactants in pMDIs?
Help suspension stability
Lubricate moving parts of the valve
