Nebulizers and PMDIs Flashcards
What is a nebulizer ?
A nebuliser is a device that converts liquid medication into an aerosol allowing it to be inhaled directly into the lungs. Nebulizers are used for direct delivery to the lungs.
Types of nebulizers
Jet Nebulizer
- most common type and uses air or oxygen to generate an aerosol. Air is blasted through a liquid medicine reservoir, creating a fine mist.
- simple and effective
- however it is noisy and requires a power source or suppressed gas supply
Ultrasonic Nebuliser
- uses high fq sound waves to create vibrations in the liquid, forming aerosol droplets.
- Quiet operation and has faster drug delivery due to higher ouput
- however, increased temperature during operation can cause degradation of heat-sensitive drugs
Vibrating mesh nebuliser
- uses a mesh with thousands of tiny holes to produce aerosol by pushing the liquid through the mesh via vibrations.
- Efficient drug delivery, high respirable fraction of dose, minimal residual volume
- However, more expensive, sensitive cleaning and maintenance
Formulation considerations
- isotonicty
- pH balance
- excipient considerations
Handling preservatives and antioxidants
Preservatives such as antioxidants are usually required to increase the shelf life of a product but are used minimally due to potential respiratory irritation.
Nebuliser packaging and usage
Solutions for nebulisation are often packaged in a single use plastic ampoules, produced using form fill seal technology, where the ampoule is formed, fiolled and sealed in a sterile environment.
The ampoule is opened just before use and the liquid is poured into the nebuliser chamber. Ensuring sterility during process is crucial to avoid contamination.
Pressurized Metered dose inhalers
- most common form of inhaled drug delivery
- active drug ingredients are dissolved or suspended in a volatile propellant.
- delivers precise dose of medication in each acutation
pMDI components
- canister = holds the drug
- propellant = traditionally CFC now replaces with HFA which are non toxic and cfc FREE
- metering valve =ensures precise volume of medication is dispensed
- actuator = plastic mouthpiece through which the aerosol is inhaled
Formulation of pMDI
PROPELLANTS = critical for aerosol formation and delivery of the drug. provide force to atomize the drug and maintain suspension stability. Eg. HYDROFLUROALKANES
SURFACTANTS = stabilize drug particles in suspension preventing clumping. Lubricate the valve to ensure smooth actuation. EG. OLEIC ACID, LECITHIN
COSOLVENTS = helps dissolve both the drug and surfactant. Adjust the density of the formulation for optimal suspension. Common solvent EG. ETHANOL
Incorrect use by pts
- not removing the protective cap
- incorrect shaking
- poor inhalation technique
- lack of coordination
SPACERS
- are extension devices that attach to pMDIs and act as a holding chamber for the medication. The aerosol from the pMDI is released into the spacer and held temporarily allowing the pt to inhale more efficiently. Reduced velocity reduces the chance of impaction.
Breath actuated PMDIs
triggers medication release during inhalation, eliminating the need for coordination. Uses a spring or vacuum system to sense patient inhalation. Ensure correct timing for drug delivery, improving efficiency and reducing wasted doses
Advantages of PMDIS
- portability
- convenience
- quick delivery
- precise dosing
- affordability
- multiple doses
Disadvantages of PMDIS
- coordination required
- inhalation technique dependant
- impaction
- environment concerns
