Pulmonary Drug Delivery Flashcards
Why is pulmonary administration used?
- treatment or prophylaxis of ariway diseases
- asthma
- cystic fibrosis
- COPD
- infection
- rapid onset of action
- smaller doses required
- useful if drug poorly absorbed orally or rapidly metabolised
- avoids FPM
- easily accessible
- non invasive
- lower proteolytic activity than GI tract
What are disadvantages of pulmonary drug delivery?
- poor reproducibility - smokers
- ability of lung marophages to engulf particles
- metabolic capacity of lung
- inefficiency of drug delivery devices
What kind of drugs are administered pulmonarily?
- bronchodilators
- corticosteroids
- anti-allergy
- mucloytics
- anti-infectives
- oxygen
What are the lungs coordinated with for oxygenation of blood?
- CNS
- diaphragm
- chest wall musculature
- circulatory system
What is the respiratory system divided into?
- nasopharynx region - nose, mouth, pharynx, larynx
- tracheobonchial region - trachea, bronchi, bronchioles - conductory region
- pulmonary region - respiratory bronchioles - respiratory bronchioles, alveoli - respiratory region
What cells are in the alveoli?
- ciliated columnar epithelial cells
- goblet cells
- submucosal glands - mucus moistens inspired air, prevents drying of walls and traps marticulate matter
What cells are the alveoli lined with?
- type 1 pneumocytes - highest SA
- type 2 pneumocytes - most cells
What is the drug delivered as pulmonarily?
aerosol: dispersion of solid or liquid in a gas
What are the three types of pulmonary drug devices?
- nebulisers - liquid or solid
- DPI dry powder inhalers - solid
- pMDI pressurised metered dose inhalers - liquid or solid
Summarise the use of nebulisers
- delivers large volumes of drug solutions and suspensions
- drug administartion during normal tidal breathing - useful for children, elderly and unconcious but
- LARGE DOSE LOST
How does an airjet nebuliser work?
compressed air carries a liquid medication through a narrow hole at high velocity turning it into an aerosol which is inhaled
How does an ultrasonic nebuliser work?
ultrasonic wave generated which vibrates a diaphragm at high frequency that is in contact with a liquid medication
high frequency vibrating converts the liquid into a vapour mist
the higher the frequency = smaller droplets
What are advantages and disadvantages of nebulisers?
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- can aerosolise most liquid medications
- allow for delivery of large doses, with limited skill by patient
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- expensive and time consuming (long periods of time)
- most drug retained in nebuliser or released into environment
- approx 10% acc reaches lungs
Summarise the use of dry powder inhalers
- metered quanitity of powder delivered
- devices are breath actuated - powder dispensed into stream of air drawn through the device by the patients own inspiratory effect
- no coordination required between activation and inhalation
- air is forced through a powder containing the drug
- turbulent air created inside powder container breaks down large particles into smaller
What is a single dose DPI?
- drug plus lactose packed in gelatin capsule
- capsules individually loaded into DPI by patient
- priming of device pierces capsule
- inhaled air flow disperses the powder from the capsule
allows the patients to remember how many doses theyve had
What is a multidose DPI?
- drug plus lactose filled into individually sealed aluminium foil blisters, with four or eight blisters per disc
- disc loaded into device by patient
- dose counter informs patients about number of doses
What is a reservoir DPI?
- powdered drug contained in a storage reservoir in the base of the device
- twisitng the base dispenses a metered dose into the dosing chamber
- up to 200 doses with dose counter
- greater effort but better lung deposition due to deeper breaths
What are the advantages and disadvantages of DPI?
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- propellant and excipient free (except lactose)
- dont need to coordinate inhalation with actuation
- most give high protection against humidity
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- energy source for delivery provided by patient (if patient has COPD etc its hard)
- dose delivered depenedent on inspiratory effect
- device operation varies between products
- not suitable for all drug formats
Summarise the use of pressurised metered dose inhalers
- drug is dissolved/suspended in one or more liquefied propellant gases
- excipients: surfactants and co solvents
- pressurised cannister fitted with a metering valve, housed in a plastic actuator
- propellant drives liquid through narrow nozzle at high velocity
propellant evaporating, propelling, shearing and reducing size of mist droplets
Why is an aerosol can not filled completely - why does it have a headspace?
temp could cause it to expand
How is the contents released immediately in a pMDI?
actuation of device depresses stem of metering valve, allowing contents to be discharged
high vapour pressure contents of metering valve immediately begins to equilibrate with atmospheric pressure
What propellants are used pMDIs?
- traditionally CFC
- non-toxic, non flammable, non reactive
- no unpleasant odour or taste
- but react with ozone
- alternatives - HFA
- no ozone depletion
What are advantages and disadvantages of pMDIS?
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- energy source for drug delivery provided by device
- dose delivered independent on inhalation
- device operation similar for all products
- high protection against humidity and contamination
- compact
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- must coordinate actuation with inhalation
- high velocity particles = substantial oropharyngeal impaction
- alternative propellants not straightforward to use
