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Advanced Drug Delivery > Oral Drug Delivery > Flashcards

Oral Drug Delivery Flashcards

1
Q

What cells are responsible for gastric acid secretion

A

Parietal cells - acidic environment ph1-3

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2
Q

Ileum characteristics

A

Ph 5-7 (most drugs absorbed here)
Large sa
Highly vascularised
Drugs may pass through li

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3
Q

Oral drug delivery advantages

A

ACCEPTABILITY
COMPLIANCE
EASE OF ADMINISTRATION

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4
Q

Oral drug delivery disadvtanges

A

BIOAVAILABILITY- variable
Certain drugs may be very hydrophobic and may be absorbed better when taken with fatty meal
Proteins will be graded in the stomach
Resukts in toxicity / sub therapeutic issue with drugs

ADVERSE ENVIRONMENT
eg mucus , peristalsis, enzymes, diff ph , gastric emptying - all make it hard for controlled release

DIFFICULTY SWOLLOWING
esp kids and elderly

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5
Q

What is modified release

A

Modulates the absorption and alters the site of release of drug - time and Space

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6
Q

Common types of mr

A

Delayed release - constant (plasma conc
Extended release - eg coating may be inert to acidic conditions. Simplifies release and may need one dose instead of two a day
Target release - similar profile to DR . React to conditions at furthest point of git

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7
Q

Advantages of mr

A

Optimised performance
Less adverse effects
Increase convenance and compliance
Improved efficacy

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8
Q

Mr dosage forms based upon what three release mechanisms

A

Dissolution
Diffusion
Osmotic

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9
Q

Dissolution mr mechanism

A

Eg encapuslated dissolution or matrix dissolution

Usually hydrophilic polymers that form a gel layer when in contact with the release media eg HPC, HPMC,
Controls passage of api from dry core to release media

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10
Q

What is drug release in dissolution method influenced by

A

Solubility
Viscosity
Hydration rate
Molecular weight

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11
Q

Diffusion systems

A

Drug moves from a more conc to less conc area through membrane. Nature of coating effects drug diffusion
Eg reservoir system (membrane controls drug release )
Most common polymer eg EC

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12
Q

Factors affecting drug diffusion through polymer

A

Lipophylicity
Mw
Viscosity

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13
Q

Osmotic APPROACH ZFOR MR drugs

A

Membrane controls the passage of water through media into the tablet
Usually resukts in the release of drug through a small hole eg basic osmotic pump ,, push pull OROS
usually consists of semi perms or membranes like cellulose acetate

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14
Q

In modelling release equation what does each component stand for
Mt/m♾️, k , t , n

A

Mt/M♾️= fraction of drug release
K= diffusion rate constant
T= time of release
N= release exponient (indicative of release mechanism ).

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15
Q

N=1 modelling release data equation

A

Drug realase is independent of time (zero order kinetics )
Rate controlling step is therefore polymer relaxation and Erosion

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16
Q

N=o.5

A

Fickian diffusion is rate controlling step

17
Q

N between o.5 and 1

A

Contribution of diffusion and polymer relaxation controlling release kinetics of swellable tablets.

18
Q

Advantage of osmotic technologies over matrix systems

A

The ability to deliver drugs with a zero order Kinetics profile independent of external factors.
(Release is constant independent to conc)

19
Q

What is release rate of osmotic systems dependent on

A

Osmotic pressure (and solubility if significant )

20
Q

What to each parameter is the osmotic equation mean

A

Osmotic e

21
Q

What does osmotic layer in push pull system usually consist of

A

Highly swellable polymer (eg High MW PEO) and osmogen (eg nacl)

22
Q

Advantages of push pull systems

A

HPI
release rate Independant of hydrodynamics
Release a rate independentcof ph
In vitro and in vivo correlation

23
Q

Why is release rate independent of hydrodynamics important

A

In vivo hydrodynamics difficult to create
As recreating gastric hydrodynamics v difficult
Hydrodynamics change in response to food , difficult to mimic In vitro

24
Q

Why is release rate in OROS independtant of hydrodynamics

A

With these systems TSH release rate is dependant on the influx of water which is controlled by the osmotic pressure and properties of the coating (i.e permeability and thickness)
So rate of stirring and the differnce of hydrodynamics between fast and fed state will not alter drug release rate

25
Q

Disadvtages of push pull systems

A

MIDD
Complex manufacturing process
Local irritation and risk of infection
Drug dumping
Patient distrust

26
Q

Why are push pull systems difficult to manufacture

A

Limited selection of excipients and polymers for the membrane and tablet core available

Bilayer tablets require a bilayer press which is expensive

Insoluble, permeable membrane required so requires sue of non aqueous solvent during coating

Laser drilling required following tablet coating (expensive and difficult to access)

Drug loading limited - ~25% of total tabket weight

27
Q

Reasons for ph sensitive coatings and example s

A

Drug may irritate the gastric mucus membrane eg NSAIDS

drug may be particularly sensitive to the acidic environment eg PPIS

Drug may need to target a particular section of GIT eg colon specific therapy wg 5-ASA for colitis

28
Q

Example of enteric polymer names

A

PVAP (polyvinyl Acetate Phthalate)
HPMCAS (hydroxypropylmethylcellulose acetate succinate)
Eudragit polymers

29
Q

Factors affecting dissolution in EC formulations

A

COATING
polymer used
Coating thickness - thicker coating can affect dissolution rate , this can be controlled
Gi tract tract sit and ph- this cannot be controlled

TABLET CORE
Physiochemical properties of api ( water solubility, particle size, ionisation etc)
Excipients combination (is disintergrants , wetting agents -i.e surfactants so that when water comes into contact with the drug it will dissolve quicker )
Processing factors eg compression force (compression high , tabket v hard, dissolution slow)

30
Q

What does gastric emptying time of tablets in fasted state range from

A

60-160 mins

31
Q

What dosage form has less variablitkty in gi transit

A

Pellets and multi unit dosage forms empty with less variability - gastric emptying times in both the fed and fasted state for pellets are similar they also present les drug dumping , particularly important for dosage forms where dose is hugh

Reduces toxicity and local irritation

32
Q

Defor oral delivery of macromolecules

A

SOMA and LUMI

Advanced Drug Delivery (2 decks)

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