Aerosols Flashcards
what are aerosols?
dispersion of fine particles or liquid droplets suspended in gas or vapor
Rationale for inhaled drug delivery
Local delivery to site of action and delivery of systemically acting drugs.
Inhaled drug delivery preferred over other forms of delivery
avoid systemic effects, rapid onset, no interaction with food, sterility, acceptability, avoid first pass metabolism and high absorption area.
Advantages of aerosol drug delivery
avoid systemic effects, rapid onset, no interaction with food, sterility, acceptability, avoid first pass metabolism and high absorption area.
Disadvantages of aerosol drug delivery
lungs generally designed to prevent inhalation of exogenous compounds, limitation of delivery of the drug (10%), irritation, taste, and reproducibility is a big concern.
Is particle size important? and if so, what happens when particle size is too small or large?
Yes it is important.If size is too large or too small, it will not allow for it to reach the site of action.
size range for aerosols
Aveolar region: 1 to 3 microns
trachea, bronchial, bronchiolar region: 3 to 10 microns
Higher up: 30 microns
Methods to measure particle size
Microscopy Sieving Sedimentation Electrical Resistance Laser Diffraction Aerodynamic diameter
Advantages of PDMI
Portable, perceived easily to use and convenient, remaining product is not contaminated during use, can be filled asceptilly, stable, tamper proof, metered dose given.
Disadvantages of PDMI
Expensive, pressurized contents (can be flammable) and prone to incorrect use.
DPI advantages
no use of propellant gas, no hand eye coordination, easy to use and no spacer, dry powder form provides stability of drug, not pressurized container, lactose carrier particles mask bitter taste of drug
DPI disadvantages
Sometimes bulky and non-portable, variable dose delivered dependent on inspiratory flow rates, not widely available, humidity protection, expensive, not all drugs available in this form.
Nebulizer advantage
does not depend on pt. inspiratory force, used mainly as aq solns, do not have to hold their breath, and less expensive in the long run.
Nebulizer disadvantage
Bulky/ not portable/ noisy, long treatment times, expensive, poorly optimized, contamination of the atmosphere, niche products.
Propellants
provide pressure to expel product, act as dispersion medium, can exhibit solvent properties.
Solvents
bringing active ingredient to soln, cosolvent for immiscible liquids, influence particle size, reduce vapor pressure.
Chlorofluorocarbons (CFC)
low toxicity, high stability, good solvents
Hydrofloroalkanes (HFA)
low toxicity, high stability, non-ozone depleting
why do we not use CFC Propellants compared to HFA?
Global warming potential is six times less than HFA. Even though HFA is more expensive.
Purpose of Surfactants
valve lubrication, aid in the dispersion of particles in suspension, stabilize foaming aerosols, emulsifying agents for emulsion aerosols, and decrease surface tension and particle size.
Propellant Aerosol
drug is dissolved vs the gas aerosol where the drug is suspended or dispersed in the propellant system
Gas Aerosol
better in the fact higher dosages can be delivered but Can be difficult to manufacture
Propellant or gas, which one is better?
Probably propellant since its simplified manufacturing. Keep in mind though the drug needs to be soluable
Inert carrier particles used in DPI
Lactose
How to use A spacer
- shake the medicine
- Insert the mouthpiece of the inhaler into the rubber sealed end of the spacer
- Breathe out. place spacer into mouth between your teeth. make a tight seal
- Press the metered dose inhaler down to release a spray of medicine. the medicine will be trapped in the spacer. breathe deeply and slowly
- hold breath for about 5 to 10 seconds and breathe out slowly
Passive DPI
Dependent on pts inhalation to provide the energy needed to disperse the powder. Usually requires pt. to inhale at max rate to work properly. This determines the dose admin.
Active DPI
Use of external energy source to generate power dispersion. Not dependent on pts efforts.
Air Jet Nebulizers
Pressurized air
Ultrasonic Nebulizers
Use high frequency vibration to generate the respirable aerosol, units compact/ generally high output, and quality of aerosol varies according to the energy supplied.