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Therapeutics > W22 Pulmonary Drug Delivery > Flashcards

W22 Pulmonary Drug Delivery Flashcards

1
Q

What is the respiratory tract broken up into

A

3 parts

upper airways

central conducting airways

respiratory peripheral pulmonary airways

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2
Q

what is the role of the lung

A

organ of external respiration in which oxygen and carbon dioxide is exchanged between blood and inhaled air

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3
Q

how big is the surface area of the lungs

A

140 metre sqaured

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4
Q

why does the lung have a large surface area

A

to help with exchange of carbon dioxide

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5
Q

what are some advantages of pulmonary drug delivery

A

can be used to treat airways disease

pulmonary administration results in rapid on set of action

smaller doses can be administered locally compared to delivery by the oral or parenteral routes

route is useful when a drug has poor absorbed orally.

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6
Q

how can we deliver a drug to the airways

A

must be presented as an aerosol except for medical gases

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7
Q

what is an aerosol

A

defined as a two phase system of solid particles or liquid droplets dispersed in air or other gaseous phase.

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8
Q

what is needed to ensure stability for an aerosol

A

small size

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9
Q

what is the aerodynamic particle diameter

A

is the diameter of a sphere with a density of 1g/cm3 that has the same aerodynamic behaviour as the particle which shall be characterized.

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10
Q

what mechanisms are responsible for particulate deposition

A

impaction

gravitational sedimentation

diffusion

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11
Q

What will particles settling under gravity

A

it will attain a constant terminal settling velocity

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12
Q

what is terminal settling velocity equal too

A

(Particle density x standard gravity x particle diameter)/ 18 x air viscosity

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13
Q

what is inertial impaction

A

dominant deposition mechanism for particle > 1 uM in the upper tracheobronchial regions. A particle with a large momentum may be unable to follow the changing direction inpired air as it passes the bifurcations and as a result will colide with the airway walls

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14
Q

impaction is proportional

A

Gravity x Raidus airway

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15
Q

What is the particle deposition affected by

A

diffusion increases as the particle size decreases

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16
Q

what are 4 factors that affect the physiological factors affecting particle deposition in the airway

A

lung morphology

oral versus nasal breathing

inspiratory flow rate

breath holding

17
Q

what is lung morphology

A

to travel down the airways, the drug particles must pass through a successive series branch tubes of constantly decreasing size

18
Q

what is oral versus nasal breathing

A

during normal nose breathing the majority of inhaled evironmental particles are deposited in the nose and pharynx. For pulmonary delivery the aerosols are inhaled via the mouth

19
Q

what is inspiratory flow rate

A

increasing inspiratory flow rate will enhance deposition by impaction in the large airways

20
Q

what breath holding

A

breath holding after inhalation enhanes the deposition of particles by sedimentation and diffusion.

21
Q

what pharmaceutical factors affect aerosol deposition

A

aerosol velocity

size and size distribution

shape

density

physical stability

22
Q

what must a drug given as an aerosol powder do

A

first needs to dissolve through the mucus layer. Dissolution may be a rate determining step, especially for poorly soluble drugs

23
Q

what is the rate of diffusion of an aerosolised powder dependent on

A

size of mucus layer

mucus viscosity

molecular size of drug

interactions between drug + mucus

24
Q

what are the advantages of pulmonary drug delivery for locally

A

dose needed to produce a pharmacological effect can be reduced compared to oral dosing

low concentration in the systemic circulation so reduced side effects

rapid onset

avoidance of GI upset

avoidance of intestinal and hepatic first pass metabolism

25
Q

what are the advantages of pulmonary drug delivery for systemically acting drugs

A

large surface area for absorption

permeability of the lung membranes towards many compounds is higher than that of small intestine and other mucosal routes

highly vascular surface promotes rapid absorption and onset of action

less hostile environment than the oral route

26
Q

what are the disadvantages for delivery of systemically acting drugs

A

complex delivery devices are regulated to target drugs to the airways and these devices may be inefficient

aersol devices can be difficult to use

various factors may affect the reproducibility of drug delivery

drug absorption may be limited due to mucus

mucociliary clearance reduces the retention time of drugs within the lungs

27
Q

what are 3 examples of current technologies that use the pulmonary route

A

pressurised metered dose

dry powder inhalers

nebulisers

28
Q

what is the most common inhalation drug delivery device

A

pMDI

29
Q

what is contained within a pMDI

A

drug dissolved in liquid propellant together with some other excipients including surfactants and preserved in a pressurized canister fitted with a metering valve.

30
Q

what happens when the drug goes to be released in a pMDI

A

when released from the canister the formulation undergoes volume expansion in the passage within the valve and forms a mixture of gas and liquid before discharge

31
Q

what is the pMDI composed of

A

container
metering valve
elastomeric seal
actuator

32
Q

what are 4 examples of propellant

A

CFCL3
CCL2F2
CCIF2CCIF2
CF3CH2F

33
Q

what are the advantages of pMDI

A

unit dosin

cheap

34
Q

what are the disadvantages of pMDI

A

use of CFCs

aerosol velocity

co-ordination difficulties

35
Q

what are the advantages of DPI

A

no coordination problems

lower drug loss by impaction

36
Q

what are the disadvantages of DPI

A

high inspiratory effort

may be required coughing reflex, less convenient than pMDI

37
Q

what are the advantages of a Nebuliser

A

generates small particles with higher delivery capacity

no coordination required

38
Q

what are the disadvantages of a nebuliser

A

inconvenient

long inhalation times

poor dose control

expensive

lack of portability.

Therapeutics (50 decks)

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