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PMP 201 Patient-Centred Learning > Pulmonary Drug Delivery I > Flashcards

Pulmonary Drug Delivery I Flashcards

1
Q

Why drugs are delivered by respiratory route

A
  • Rapid onset activity and local effect (brochodialators salbutamol)
  • Smaller dose needed more economical
  • High bioavailability as high first pass met
  • High lung surface area and good blood supply systemic delivery
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2
Q

Pulmonary drug delivery

A
  • Drug physicochemical
    properties
  • Formulation
  • Patient
  • Delivery system
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3
Q

Importance of particle size

A
  • Solid particles suspeneded in air or liquid in air
  • Gas administer via pulmonary route oxygen or anesthetic
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4
Q

Measuring partical size

A
  • Physical diameter = Particle density/ unit density
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5
Q

Aerodynamic diameter

A
  • The diameter of a sphere of which settles through air with a velocity equal to that of the particle in question
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6
Q

Limitations of repiratory route

A
  • Evolved to inhale specific gases and not forigen particles
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7
Q

Inertial impaction

A
  • Occours in upper airways and velocity and mass of particles cause impact on airways surface
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8
Q

Impaction dependant on

A
  • Particles momentum
  • Position of particles in airstream
  • Angle of bifucation
  • 10 micrograms 50% deposition
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9
Q

Sedimentation

A
  • Suspened in gas subject to vertical gravitational force
  • Mechanism of depositing in lower airways
  • Sedimentation less relevet when particle size decrease
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10
Q

Diffusion

A
  • Particles <0.5 microgram
  • ## Smaller particles more deposition in peripheral lung and alveolar space
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11
Q

Minor mechanism of deposition

A
  • Inception of elongated particles
  • Charge reflection of charged particles
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12
Q

Structure of airways

A
  • Up to 6x10^8 alveoli in lungs
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13
Q

Drug Delivery Devices

A

– Pressurised metered-dose inhalers
– Dry powder inhalers
– Nebulisers
– Electronic cigarettes

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14
Q

Pressurised metered-dose inhalers

A
  • Delivery of adrenaline or isoprenaline (medihaler)
  • β2-receptor agonist
    salbutamol
  • Dispersed in the liquid propellant via solution or suspension
  • Actuation of a metering valve
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15
Q

Pressurised metered-dose inhalers

A
  • Canister that is aluminium
  • Metering valve control volume delivered
  • Propellant: hydrofluoroalkanes HFA-134a and HFA-227
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16
Q

State of propellents used inhalers

A
  • Liquified gases as pressure causes conversion of liquid in canister to gas when actuated
17
Q

Filling of pMDI canisters: Cold filling

A
  • Drug, excipient and propellent chilled - 60 degrees
  • Further chilled and added to canister sealed with valve
  • Leak tested placed in water bath and weighed
18
Q

Pressure filling

A
  • Ethanol can be used before valve crimped in place
  • Drug + excipients + propellant
    added to canister under
    pressure
  • Further propellent added under pressure
  • Leak tested in water bath and weighed
19
Q

Formulation of pMDIs: Greenhouse gas

A
  • chlorofluorocarbons contain in original pMDIs but damage to ozone layer
  • Replace with hydrofluoroalkanes
  • Still geenhouse gas must be phased out
20
Q

Formulation of pMDIs: Use of surfactant

A
  • Dispersed in the propellant as a solution/ suspension
  • HFA-134a and HFA-227 exhibit low relative permittivity values so are not good solvents
  • Surfactants may be required as suspending agents E.G. Lecithin, Oleic acid, Sorbitan trioleate
21
Q

Co-solvents used in pMDIs

A

Ethanol, 2-propanol, can be added to aid solubility of drugs and excipients

22
Q

beclometasone pMDIs

A
  • Dissolved in the propellant this can lead to very small particles (more potent)
23
Q

Sustainability of pMDIs

A
  • Bulky dosage forms use plastic and aluminium
  • Can be recyclable but no national recycling scheme exist
24
Q

Ventolin vs Salamol

A
  • Ventolin high carbon footprint
  • Salamol lower carbon footprint and high global warming potential
25
Q

Advantages of pMDIs

A
  • Portable
  • Low cost
  • Drug protected in canister
  • Multipe dose in one device
  • Reproduceable dose Efficient at drug delivery
  • Disposable
26
Q

Disadvantages pMDIs

A
  • Incorrectly used by patient
  • Greenhouse gases

PMP 201 Patient-Centred Learning (51 decks)

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