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Pharm304 > Pulmonary drug delivery > Flashcards

Pulmonary drug delivery Flashcards

1
Q

What is pulmonary drug delivery?

A
  • delivery of drugs to the lungs

- systemic and local options

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2
Q

What are the preferences for local or systemic drug delivery to the lungs?

A
  • local delivery is currently more widely utilised

- however use of pulmonary route is growing for systemic delivery to replace parenteral injections.

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3
Q

What is the basic anatomical structures of the lungs?

A
  • pulmonary bronchioles,
  • secondary bronchioles
  • tertiary bronchus
  • bronchiole
  • terminal bronchiole,
  • alveoli
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4
Q

What is the fate of inhaled drugs?

A
  • if delivered to upper respiratory tract to achieve effect on local tissues, it will then go into the GIT where there is drug degradation, metabolism and some systemic effects
  • if it goes into the conductive airways also for local activity, it mag go int othe GIT or blood (via pulmonary circulation to systemic circulation)
  • if it goes into the alveolar region (for systemic delivery), it will then go into the blood and to the systemic circulation
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5
Q

What parameters determine particle deposition in the lung?

A
  1. aerodynamic particle behaviour
  2. breathing pattern
  3. timing of drug bolus in breathing cycle
  4. patient specific airway anatomy and morphology
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6
Q

How does aerodynamic particle behaviour determine particle deposition?

A

-particles can undergo 3 main behaviours?

  • diffusion: significant behaviour for particles <0.5um in terminal airways
  • sedimentation: for particles 0.5-3um

-impaction: for particles .5um

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7
Q

What is impaction?

A

prevents particles reaching further than the large conducting airways as inhaled air goes into the lungs, larger particles may not make the turn and so will impact on to the wall of the respiratory tract

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8
Q

What is sedimentation?

A
  • where particles fall at a terminal velocity as air resistance equals the force due to gravity
  • stokes sedimentation law can be reviewed to change this rate.
  • increased size = faster sedimentation but increases impaction
  • altering air flow will also alter velocity to allow particles to sediment properly (achieved by holding your breath)
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9
Q

What is diffusion?

A
  • diffusion or brownian motion predominates for particles of <0.5um
  • occurs predominantly in peripher
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10
Q

How do breathing patterns determine particle deposition in the lung?

A
  • fast inhalation results in significant impaction for particles >3um. (large patient intervariability)
  • slow inhalation particles >10um can enter the lungs
  • ideal breathing pattern can promote residence time in the lungs
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11
Q

What is resident time of particles in the lungs important for?

A

sedimentation and diffusion

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12
Q

How can residence time be promoted with breathing?

A

breathe deeply and hod the breath for 10 seconds

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13
Q

How does the timing of the drug bolus in the breathing cycle of the patient determine particle deposition in the lung?

A
  • some patients may inhale the drug at different parts of the breathing cycle (e.g. earlier or later in the breath)
  • can change the deposition profile
  • some delivery systems deliver bolus at predetermined times in the inspiration breath for this reason.
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14
Q

How does patient specific airway anatomy and morphology determine particle deposition in the lung?

A
  • disease state (asthma, COPD)
  • changes to mucous layer
  • changes in epithelial thickness and permeability
  • airflow changes, all vary from patient to patient, and may act as barriers in the inhalation of drug particles.
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15
Q

What diseases are treated with local pulmonary drug delivery?

A
  • asthma (e.g. salbutamol)
  • COPD
  • bronchial trumours
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16
Q

What are the advantages of local pulmonary delivery?

A
  • rapid onset of activity for local action
  • smaller doses can be administered compared with oral and parenteral routes (less side effects)
  • useful when drug is poorly absorbed orally (e.g. sodium cormoglycate) or if drug is metabolised following oral absorption (e.g. isoprenaline)
17
Q

What is systemic pulmonary drug delivery used for?

A

to target the alveolar region which would allow it to enter the systemic circulation
-an alternative route of delivery for many drugs labile to enzymatic degradation and FPM

18
Q

What are the advantages of systemic pulmonary drug deliery

A
  • large surface area availably (70-140m^2) c.f. other routes for non oral systemic delivery
  • high vascularisation
  • thin alveolar epithelium
  • high rate of solute exchange
  • avoidance of FPM
19
Q

What is the distance between bronchial system from mucous surface to the blood?

A

30-40um

20
Q

What is the distance in alveolar region from air to blood?

A

0.5-1um

21
Q

How thick is the alveolar epithelium?

A

0.1-0.2um

22
Q

What are the challenges of systemic drug delivery?

A
  • lack of reproducibility in deposition of dose
  • differing absorption rates and extent due to different thicknessess in epithelial lining
  • protective filtering effect of oropharyngeal region and bronchial tree
23
Q

What is Aradigm?

A

an aerosol pulmonary delivery device

  • delivers liquid formulations to the lungs
  • has a control over particle size:
  • regulates patients inhalation rate and timing or dose during the inhalation
  • claimed to be 4-5x more efficient than nebulisers to deliver drugs into patients lungs
  • delivery rate to target tissues still reported to be 50%
24
Q

How does the AERx pulmonary delivery device control the particle size?

A
  • there are about 300-450 laser drilled holes in the aerosol nozzle array
  • drug solution is extruded through holes resulting in 2-5um particles
  • depending on target areas in lungs, hole diameter can be controlled
25
Q

What effect does the hole size have on AERx?

A

-larger holes = larger particles = to target the upper airways

26
Q

What is the background on pulmonary delivery of opioids?

A
  • humans have history of social and misuse of opioid inhalation
  • systematic administration often indicated for management of severe pain
  • most effective analgesia is produced by IV patient controlled analgesia but faces issues with inconvenience, maintenance and infection risk
  • common non-invasive routes such as oral, bucca, transdermal routes have a longer onset of action
  • pulmonary delivery of opioids has potential to provide effective treatment of severe acute and breakthrough pain
27
Q

Which opioids are commonly used in pulmonary delivery?

A

Morphine

Fentanyl

28
Q

What is the effect of pulmonary delivery of morphine?

A

Depends on the delivery method, but if administered by the pulmonary route, can reach the systemic circulation rapidly and reproducibly

29
Q

What are the implications with the pulmonary delivery of fentanyl?

A
  • fentanyl is moe Lipophilic than morphine so we expect good systemic delivery following pulmonary administration
  • but instead, it displayed poor bioavailability via the Acon nebuliser
  • indicating importance of delivery method to get rug to desireable areas of the lung
  • AERx device was able to achieve rate and extent of absorption following pulmonary administration of fentanyl similar to IV
30
Q

What is the disadvantage using AERx device to deliver fentanyl via the pulmonary route?

A

A larger dose is needed to compensate for the predicted 60% Kung delivery efficiency –> expensive

31
Q

What are the implications with the use of liposomal entrapment to deliver fentanyl via the pulmonary route ?

A

Depending on the entrapment efficiency, release profiles can be designed comprising an immediate release component and a sustained release component

Following deposition of the formulation in the lungs, drug absorption of the entrapped drug is delayed.

32
Q

What are the reasons by Exubera - inhaled insulin- failed in the market?

A
  • cumbersome design which had difficulty adjusting doses to meet lifestyle demands
  • was as effective as injectables but more expensive than needle systems, and current well developed needle systems cause minimum of pain and discomfort
  • insulin is traditionally administered in units, but Exubera relies on mg dosing and 1mg approximately equates to 3 units, but increase is not linear with reference to units which was confusing
33
Q

What is the ideal particle size for pulmonary drug delivery?

A

<5um

34
Q

How can the particle si: from delivery devices like MDI, PDI, AERx be assessed?

A

…

35
Q

How can dissolution of pulmonary drug delivery be assessed?

A

…

Pharm304 (21 decks)

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