amorphous solid dispersions and inhaled medicine Flashcards

1
Q

requirements for oral drugs

A

good solubility and dissolution rates, good absorption through gut (permeability)

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2
Q

what does bioavailable mean

A

proportion of drug that enters circulation, when introduced to the body, that has an active effect

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3
Q

oral formulations for poorly water soluble componuds

A

-salt formation
-reduce particle size
-SEDDS (self emulsifying drug delivery system
-complexes (wrap drug in soluble structure)
-nanoparticles (increases SA:V)
-crystalline solid dispersions
-amorphous solid dispersion (disrupts crystalline structure to form disordered amorphous state, disolutes faster)

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4
Q

how do amorphous solid dispersions work as a oral formulation

A

disrupts ordered crystalline state to form a disordered amorphous state that dissolute more rapidly

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5
Q

what is glass transition (Tg)

A

transition of an amorphous material from brittle to rubbery

-lower Tg=less stable=more likely to recrystallise

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6
Q

2 ways to manufacture solid dispersions

A
  1. solvent based- spray drying
    -rapid solvent evaporation, needs acceptable solubility of drug in low boiling solvent
  2. heat based- holt melt extrusion
    -temperature can cause degradation, no solvent required, melting point of less than 200 needed
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7
Q

techniques to test formulation

A
  1. DSC (differential scanning calorimetry)- tests mp
  2. X ray crystallography- detects ordered molecular organisation of crystals
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8
Q

why use amorphous form of a drug

A

improves properties like bioavailability and dissolution rates

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9
Q

structure of lungs

A

trachea, bronchi, bronchioles, alveoli
SA increases —>

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10
Q

why deliver drugs to lungs

A

-local and systemic effects
-rapid action
-more comfortable for patient
-smaller doses than oral so there will be less adverse effects

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11
Q

what is an aerosol

A

suspension of liquid or solid particles in a gas

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12
Q

why is using an aerosol good

A

overcomes barriers, penetrates to airways

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13
Q

what makes an effective aerosol particle

A

-deposits in the right lung region
-right quantity
-overcomes physiological barriers and respiratory defence mechanisms

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14
Q

what is aerodynamic diameter

A

diameter of a sphere with density 1gcm^3 that has the same settling velocity in the air as the particle of interest

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15
Q

aerodynamic diameter equation

A

d(aer)= d√p/p1

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16
Q

what is stokes law equation

A

v=(1/18n)d^2pg

v=settling velocity
n=viscosity
d=particle geometric diameter (um)
p=density (gcm^3)
g=gravitational acceleration

17
Q

what determines the stie of particle deposition in lungs

A

aerodynamic diameter and stokes law, air flow

18
Q

what is respirable fraction

A

percentage of drug present in aerosol particles that is likely to be deposited

19
Q

what can be used to determine the respirable fraction

A

Anderson cascade impactor or next generation impinger

20
Q

name and explain 3 types of inhalers and how they are aerolised

A

nebulisers-aqueous drug solution aerolised into droplets, energy provided by compressed air or ultra sound

pMDI- drug formulated into liquified gas under pressure, forms aerosol by evaporation of gas at atmospheric pressure

DPI- drug and other solid excipients in a dry powder state, no solvent, aerolisation by patient inhaling

21
Q

what does pMDI stand for

A

pressurised metered dose inhaler

22
Q

what does DPI stand for

A

dry powder inhaler

23
Q

how do pMDI form aerosol

A

evaporation of gas at atmospheric pressure

24
Q

problems with pMDI

A

-patient must coordinate inhaling and pressing
-particles leave with high velocity leading to high deposition in oro-pharynx (back of throat) and low deposition in lungs
-can be improved by using a spacer

25
problems with DPI
-dose delivered and deposited is dependent on patients inspiratory flow which is hard to predict and replicate -particles need to be <5um to penetrate lungs but small particles are very cohesive (will stick together) -moisture increases agglomeration (clumping)
26
solutions to DPI
-spherical particles to reduce contact point -protect from moisture -blend drug with carrier with large particle size, drug must be separated from carrier to be inhaled (mostly lactose used) ^large lactose particles deposited in the back of throat and drug deposits in lungs
27
types of DPI
-unit dose device -multiple unit dose device -reservoir device
28
advantages and disadvantages of nebulisers
advantages -no coordination needed -suitable for emergencies -combination of different substances are possible -for all age groups disadvantages -not portable -pressurised gas needed -long treatment time -regular cleaning required -expensive
29
advantages and disadvantages of pressurised metered dose inhalers
advantages -portable, compact -dose and particle size independent of inhalation -can be used in emergencies -short treatment time (acts fast) -available for most substance disadvantages -coordination needed -ages 6 and up -no control of dose -propellent required -high deposition in oro-pharynx
30
advantages and disadvantages of dry powder inhalers
advantages -small, portable -breath actuated -less coordination -short treatment time -available for most substances -stable as there's no solvent disadvantages -ages 4 and up -not for emergencies -sensitive to humidity -pharyngeal deposition -high inspiratory flow required