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Pharmaceutics 2 Winter Final > 4 - Pulmonary > Flashcards

4 - Pulmonary Flashcards

1
Q

Do you want a drug to stay in the oropharynx? Why or why not?

A
  • No
  • Drug deposited in oropharynx is swallowed and absorbed, leading to systemic exposure and potential systemic adverse effects
  • Can also cause local adverse effects (ex: candidiasis, hoarseness)
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2
Q

Who may benefit from using a spacer?

A

Px w/ poor coordination, poor lung function, or arthritic joints

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3
Q

What type of propellants were previously used and what type are now used? Why was this changed?

A
  • Used to use chlorofluorohydrocarbons (CFCs)
  • Now use hydrofluoroalkanes (HFA)
  • CFCs cause atmospheric damage to ozone layer
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4
Q

Which dosage routes can aerosols be used for?

A
  • Pulmonary
  • Sublingual
  • Dermal
  • Rectal
  • Vaginal
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5
Q

Aerosols are ____ phase systems consisting of _____ and depend on _____ to expel contents

A
  • 2 phase systems
  • Consist of droplets or particulates dispersed in air
  • Depend on compressed or liquefied gas
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6
Q

How can aerosols be dispensed?

A

Fine wet spray, foam, semisolid stream, or dry particles

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7
Q

How are drugs added to aerosols?

A

Dissolved, suspended, or emulsified in propellant or mixture of solvent and propellant

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8
Q

What is the epithelium like in the respiratory tract?

A

Varies in thickness and permeability (thick trachea; more permeable alveoli)

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9
Q

How are different types of drugs absorbed in the respiratory tract?

A
  • Hydrophobic molecules absorbed through transcellular pathway of lipid bilayer around cells
  • Hydrophilic molecules subject to paracellular absorption through aqueous pores in intercellular tight junctions
  • Some molecules subject to active transport
  • Absorption profile of an inhaled molecule is culmination of all these routes of absorption
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10
Q

Pulmonary drug delivery is determined by….

A
  • Nature of active ingredient
  • Formulation
  • Device
  • Functional performance in aerosolization
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11
Q

Important feature of inhaled drugs is ______. Why?

A
  • Particle size of dose components

- Large particles won’t reach deep lung tissue; small particles risk being exhaled

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12
Q

What is the function of respiratory epithelial cells?

A
  • Regulate respiration

- Produce airway lining fluid

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13
Q

What is the surface area of the respiratory mucosa?

A

70-140 m^2 in adults

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14
Q

What are the divisions in the respiratory tract?

A
  • Bronchi
  • Bronchioles
  • Terminal bronchioles
  • Respiratory bronchioles
  • Alveolar ducts
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15
Q

The deeper the passageways of the respiratory tract go, _____ decreases and _____ increases

A
  • Diameter decreases

- Surface area increases

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16
Q

What happens when inhaled particulate substances enter the airways?

A

Once deposited in airways, particles are carried by mucociliary system and degraded or absorbed into systemic circulation or lymph ducts

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17
Q

What is found on airway surfaces from trachea to terminal bronchioles?

A
  • Ciliated epithelium covered by mucous

- Mucous is biphasic (2 layers) – low-viscosity periciliary layer and thicker gel layer on top

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18
Q

What is the purpose of the biphasic mucous layer of the respiratory tract?

A
  • Protects epithelium from dehydration
  • Helps humidify air
  • Protective mechanism to trap inhaled particles
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19
Q

What happens to insoluble particles in the respiratory tract?

A
  • Trapped and moved toward larynx where they are either coughed up or swallowed
  • Consumed and eliminated by alveolar macrophages
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20
Q

What determines the clearance speed of the respiratory tract?

A
  • Number and beat frequency of ciliated cells

- So factors that influence function of cilia or quantity or quality of mucous affects rate

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21
Q

What happens to soluble particles in the respiratory tract?

A

Eliminated by absorptive mechanisms into systemic circulation, bronchial circulation, or lymphatic system

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22
Q

Where is the rate of absorption the fastest in the respiratory tract?

A

Alveolus

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23
Q

Where is the greatest membrane permeability in the respiratory tract?

A

Alveolus

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24
Q

What are advantages to pulmonary administration?

A
  • Avoids first-pass effects in GI tract and liver
  • Used for local effect, so dose is smaller and potential SE are avoided
  • Large surface area, excellent blood supply, and permeable mucosa make route an alternative to parenteral
  • Rapid onset especially for local effect
  • Convenient delivery systems
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25
Q

What are disadvantages to pulmonary administration?

A
  • Some systems (ex: pMDI) require coordination by patient to time actuation of device and inhalation
  • Dry powder inhalers require px to generate aerosol using inspiratory flow, so not suitable for very young and very old
  • Dose of drug must be small
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26
Q

What determines the fate of inhaled particles?

A
  • Physicochemical characteristics
  • Deposition site
  • Biological defences like mucociliary transport and airway macrophages
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27
Q

Which drug factors affect absorption through airway epithelium?

A
  • Molecular weight
  • Hydrophobicity
  • pH
  • Charge factors
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28
Q

What is the goal of pulmonary drug delivery?

A

Achieve high lung deposition in target region for either local or systemic effect

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29
Q

Is airflow direction and velocity the same throughout the respiratory tract?

A

No, decrease from laminar to stagnant in alveolar region

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30
Q

What are the processes of particle deposition in airways?

A
  • Inertial impaction
  • Gravitational sedimentation
  • Brownian diffusion
  • Interception
  • Electostatic attraction
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31
Q

What is the normal size of particles of aerosolized drugs? How does this affect deposition?

A
  • Greater than 1 um

- Main mechanisms of deposition are impaction and sedimentation

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32
Q

How does size of particles affect location of deposition?

A
  • Larger than 10 um deposited in oropharynx
  • 5-10 um deposited in central airways
  • 0.5-5 um deposited in small airways and alveoli
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33
Q

What size of particles is best for topical respiratory treatment? What is this called?

A
  • 0.5-5 um

- Breathable fraction of an aerosol

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34
Q

What is mass median aerodynamic diameter (MMAD)?

A

Diameter at which 50% of particles by mass are larger than 50% are smaller

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35
Q

What is geometric standard deviation (GSD)? How is it calculated?

A
  • Measure of spread of an aerodynamic particle size distribution
  • GSD = (d84/d16) ^1/2
  • d84 and d16 represent diameters at which 84% and 16% of aerosol mass are contained, respectively, in diameters less than these diameters
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36
Q

When does inertial impaction occur?

A
  • Particles w/ high momentum collide w/ airway wall
  • Happens in first 10 bronchial generations
  • Associated w/ rapid speed and diameter equal to or larger than 10 um
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37
Q

Which devices tend to cause drugs to be retained in oropharyngeal region?

A
  • Dry powder inhalers

- Pressurized metered-dose inhalers

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38
Q

When does interception occur?

A
  • When particles are fiber shaped

- Due to their elongated shape, deposited as soon as they come in contact w/ airway wall

39
Q

When does electrostatic deposition occur?

A

Charged particles

40
Q

What is gravitational sedimentation? Where is it most likely to occur

A
  • Particles w/ sufficient mass are deposited due to force of gravity
  • Predominates in last 5 bronchial generations, where air speed is slow and residence time is longer
41
Q

What is Brownian diffusion? What particles does it affect? What happens to these particles?

A
  • Particles move erratically due to Brownian diffusion
  • Affects particles smaller than 0.5 um when they reach alveolar spaces where air speed is practically zero
  • Particles are expelled on exhalation and not deposited
42
Q

What determines air flow in the lungs?

A

Tidal volume and respiratory rate

43
Q

What is the effect of airflow velocity in the first four generations of the respiratory tract? What happens below these generations?

A
  • Deposition for any size particle increases as inspiratory flow increases
  • Beyond this, airflow is reduced and no longer laminar
44
Q

When does particle deposition by impaction increase?

A
  • Larger particles
  • Inspiratory airflow is greater
  • Angle separating two branches is wider
  • Airway is narrower
45
Q

How does chronic bronchitis or asthma affect deposition of aerosolized drugs?

A
  • Bronchoconstriction
  • Inflammation
  • Secretion accumulation
  • Smaller caliber of airway increases air speed and produces turbulence where flow is usually laminar
46
Q

What does airway obstruction cause?

A

Causes air to be displaced toward unobstructed areas, therefore drug will tend to deposited in healthy areas of the lung

47
Q

What happens when particles are hygroscopic?

A
  • Absorb humidity, so get larger upon entering the airway
  • Diameter that a particle reaches after hygroscopic growth depends on initial diameter, intrinsic properties of particle, and environmental conditions in airways
48
Q

What is the property of hygroscopicity used for?

A

To try to manage deposition pattern of inhaled drugs

49
Q

Where are beta 2 receptors located in the lungs?

A

Majority in alveolar walls; large amount in airway between main bronchi and terminal bronchioles

50
Q

Where are the majority of M3 muscarinic receptors located?

A
  • Alveolar walls
  • Submucosal glands and lung lymph nodes
  • Lower proportion in smooth muscle of airways
51
Q

Where should muscarinic receptor antagonists (ipratropium bromide), beta 2 agonists (salbutamol), antibiotics and corticosteroids be deposited?

A
  • Muscarinic antagonists = conducting airways
  • Beta 2 agonists = middle and small airways
  • Antibiotics = depends on disease being treated
  • Corticosteroids = throughout the lungs
52
Q

What are the devices currently used for administration of inhaled drugs?

A
  • Pressurized metered-dose inhalers
  • Dry powder inhalers
  • Nebulizers
53
Q

What are advantages to metered-dose inhalers?

A
  • Release a fixed dose of medication w/ each pulse
  • Small size, easy to handle, inexpensive
  • Possibility to fit spacer chambers
54
Q

Do metered-dose inhalers contain a suspension or a solution of drug?

A

Either or

55
Q

What size and what speed do metered-dose inhalers release drugs?

A
  • High speed, over 30 m/s

- Particles or droplets w/ a diameter between 1-5 um

56
Q

What are disadvantages to metered-dose inhalers?

A
  • Difficulty in synchronizing activation and inhalation
  • Low dose reaches lungs; over 80% of dose undergoes intertial impaction and largely retained in oropharyngeal region
  • Possible variation in dose if formulation is a suspension and device isn’t shaken
57
Q

What is the optimal technique to use a metered-dose inhaler? Why is this method optimal?

A
  • Exhale
  • Activate inhaler
  • Inhale slowly and deeply
  • Hold breath for 5 seconds
  • Increases deposition by sedimentation in more peripheral areas of airway
58
Q

What can be used to help when coordination is an issue?

A

Spacer

59
Q

What are advantages to spacers?

A
  • Aerosol goes into chamber and remain suspended until inhaled by px
  • Allows aerosol to lose speed thereby reducing impaction against oropharynx and reducing local adverse effects
60
Q

What were dry powder inhalers designed to do?

A

Eliminate inherent coordination difficulties of pMDIs

61
Q

DPI administer doses in a powder form contained in….

A
  • Capsules broken prior to administration
  • Blisters broken open before administration (unidose systems)
  • Powder reservoirs (multidose systems)
62
Q

Do DPIs contain propellants?

A

No

63
Q

Do pMDIs or DPIs allow more drug to reach the lungs?

A

Both about the same; less than 20% of initial dose actually reaches lungs

64
Q

How is aerosol generated w/ a DPI?

A

By the inhalation effort of the patient

65
Q

What is the normal diameter of particles from a DPI?

A

1-5 um

66
Q

What are the 2 types of nebulizers? What is the difference between them?

A
  • Jet
  • Ultrasonic
  • Differ in mechanism used to generate aerosol
67
Q

What is the normal size of droplets from a nebulizer?

A

1-5 um

68
Q

What px are nebulizers used for and why?

A
  • Don’t require px coordination between inhalation and actuation
  • Used for pediatric, elderly, ventilated, non-conscious px; those unable to use pMDIs or DPIs
69
Q

What is an advantage to nebulizers?

A

Deliver larger doses compared to other aerosol devices, but require longer administration times

70
Q

What occurs in jet nebulizers? What do they require?

A
  • Airstream moves through small capillary tube at high velocity creating a low pressure that drives liquid up capillary tube
  • Require a compressor
71
Q

What occurs in ultrasonic nebulizers? What do they require?

A
  • Sound waves created due to vibration of piezoelectric crystals at high frequency, creating crests that break liquid into small droplets
  • Require electricity
72
Q

What are disadvantages of nebulizers?

A
  • Have to be assembled and loaded prior to use and then disassembled and cleaned
  • May be difficult for elderly
73
Q

What are the contents of a pMDI?

A

Propellant and therapeutic agent

74
Q

What happens following actuation of a pMDI?

A
  • Droplets about 40 um are released; volume released is usually 25-100 uL
  • Propellant evaporates quickly, leaving solid particles which are deposited into respiratory tract when px inhales slowly and deeply
75
Q

What happens if a pMDI is a suspension?

A

Particle size of drug will have been reduced by milling size necessary for delivery to appropriate part of respiratory system

76
Q

What is the purpose of propellants?

A

To drive medication out of device then evaporate quickly to allow particle to be inhaled and deposited in correct location

77
Q

What are propellants made of and why?

A

Typically a blend of 2 hydrofluoroalkanes (HFAs) to ensure pressure is sufficient to expel material and rate of evaporation is suitable

78
Q

What is added if excipients are needed for pMDIs?

A

Sometimes alcohol is added to ensure solubility of excipient

79
Q

Why are excipients needed for suspensions?

A

Prevent caking and agglomeration

80
Q

What is the purpose of excipients for pulmonary suspensions?

A

Decrease electrostatic charges between particles, preventing agglomeration and adhesion to container or valve

81
Q

What are some examples of non-ionic surfactants for pulmonary use?

A
  • Sorbitan trioleate (span 85) and sorbitan tristearate (span 65)
  • Lecithin and oleic acid also used but need some ethanol to solubilize them
82
Q

What is a disadvantage to HFA propellants? How can this be overcome?

A
  • Many drugs have limited solubility in HFA propellants

- Alcohol may be added as a cosolvent

83
Q

How can ethanol concentration influence pulmonary drug delivery?

A
  • Changes formulation density and thus total mass atomized
  • Changes size of atomized droplets
  • Changes evaporation rate of droplets
84
Q

What else can be used to enhance solubility in pMDIs?

A

Spans, tweens, and PEGs

85
Q

What excipient is commonly used in DPIs?

A

Bulking agent (lactose commonly used, mannitol is also an option)

86
Q

What is the common size of lactose used in DPIs? Why?

A

30-60 um to ensure it doesn’t enter lower airways

87
Q

How are drug particles detached from the surface of carrier particles?

A

By energy of inspired flow that overcomes adhesion force between drug and carrier

88
Q

What is the vehicle for nebulizers? Why?

A

Water for injection b/c nebulizers are sterile

89
Q

What is the ideal pH for nebulizers? What is needed if this pH isn’t achieved?

A
  • Over pH 5

- 5 or under requires buffering since can cause bronchoconstriction

90
Q

Solutions for nebulizers must be ___tonic b/c ____

A

Isotonic b/c hyper or hypotonic can cause bronchoconstriction

91
Q

What are some tonicity adjusting agents?

A

Sodium chloride, mannitol, dextrose

92
Q

What is an example of an antioxidant?

A

Sodium bisulfite

93
Q

Which non-invasive dosage route provides the best bioavailability?

A

Pulmonary

94
Q

Which non-invasive dosage route provides the fastest onset of action?

A

Pulmonary

Pharmaceutics 2 Winter Final (9 decks)

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