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Pharmaceutical formulation and quality assurance > Advanced drug delivery: Oral route > Flashcards

Advanced drug delivery: Oral route Flashcards

1
Q

what are the aims of new technology in oral drug delivery?

A

Deliver drug at peak time
Deliver in the part of the GI they are best absorbed at
Deliver continuously along the GI

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2
Q

which organs are most of the drugs absorbed in

A

Duodenum
Jejunum 1
Portal vein tract

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3
Q

what are the physiological factors that affect oral bioavailability?

A 
Transit time
pH
Microflora
Enzymes
Redox potential
Presence of solids and liquids
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4
Q

what does the transit time of a drug correspond to?

A

The amount of time the drug is in contact with the mucosa for absorption.

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5
Q

What are the transit times in the stomach, SI, and colon?

A 
SI = 3-5 hrs
Colon =8-15 hrs - longer due to movements that happen (retrograde)
The stomach: extremely variable
  *30min d<2mm and liquids
  *3h d>7mm, up to 10h with heavy meal
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6
Q

What factors affect transit time

A 
size
 density
 dietary intake (fat)
 posture- sitting/ lying down/very mobile
 gender
 age
 exercise
 emotional state
 stress
 disease
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7
Q

What type of contractions and movement occur in the colon?

A

Retrograde contractions: retaining and mixing luminal content for prolonged time
Annular contractions: Divide up faecal mass
Segmenting movements
Propulsive movements

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8
Q

What are the pH’s along the stomach, SI and Large intestine ?

both fasted and fed

A 
Stomach:
 -Fasted: 1.5-3
 -Fed: 2-5
SI:
 -Fasted: 6.1
 -Fed: 5.4
 -Ileum:7-8
Large intestine
 -Caecum and colon: 5.5-7
 -Rectum:7
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9
Q

What are the count of bacteria along the Gi tract

A

Saliva: 10^7 (aerobes + anaerobes)

Stomach:10^4-10^8 fed; ~ 0 fasted

Small intestine: Duodenum:10^3-10^4 (peristalsis and bile)

Colon: 10^11, only anaerobes

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10
Q

Which enzymes are found in which part of the GI tract?

A

Small intestine:
>Pancreatic secretions- Esterases, lipases, amylases, proteases, nucleases
>Brush border- Glycosidases, disaccharidases

Colon: specific enzymes that breaks down which have been broken down before
> Di-tri-saccharidases, mucoplysaccharidases, b-gucuronidases, b-xylosidases, a-arabinosidases, b-glucosidases, nitroreductases, azoreductases, deaminases, hydroxylases

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11
Q

What is the redox potential in the SI and colon?

A

SI: -69±90 mV
Colon: -415±72 mV

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12
Q

HoW does the presence of food and liquids affect the drug delivery?

A
  • It delays gastric emptying
  • Drug binding and complexation (tetracyclines + Ca2+ from dairy products)
  • Splanchnic (internal organ) blood flow increased  reduced 1st pass metabolism
  • The amount of liquid present in the lumen decreases along the GIT and it is minimum in the colon
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13
Q

How does the presence of food and liquids affect the drug delivery?

A
  • It delays gastric emptying
  • Drug binding and complexation (tetracyclines + Ca2+ from dairy products)
  • Splanchnic (internal organ) blood flow increased  reduced 1st pass metabolism
  • The amount of liquid present in the lumen decreases along the GIT and it is minimum in the colon
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14
Q

What are the advantage of oral drug delivery route

A

> Convenience and compliance
Large surface area for drug absorption
Rich blood supply for distribution
Peristaltic movement in the stomach is good for mixing
Prolonged retention
Different types of formulations available

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15
Q

What are the disadvantage of oral rug delivery route?

A 
There is variability along the GI tract
ADRs can occur
High enzyme activity
1st pass metabolism
Extreme pH and pH changes
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16
Q

What current technologies are available for oral delivery?

A

> Conventional dosage forms: tablets, capsules, supensions, emulsions, solution, etc.

> Prodrugs

> Advanced tablet formulations

> Advanced pellet formulations

> Advanced capsule formulations

> pH responsive formulations

17
Q

what are Pro-drugs and their purpose

A

They are compounds resulting from the modification of a biologically active compound.

prepared in order to:

> increase absorption (adding lipophilic moieties)

> protect from enzymatic degradation

> avoid premature absorption (colonic delivery)

18
Q

List the types of advanced tablet formulations?

A
  1. Osmotic tablets
  2. Gellable barrier layers
  3. Erodible barrier layers
  4. Tablet rupture
19
Q

Describe the structure and the way osmotic tablet work.

A

They have a core and a semi-permeable membrane

Water from stomach enters through the membrane to the core.

The drug dissolved and pumps out through the exit orifice.

Osmotic agents: NaCl, hydrophilic polymers

20
Q

How do the push-pull osmotic system work

A 
Has Capsule shape with layers
>2-laser-drilled deliver orifice
>Drug compartment 1 
>Drug compartment 2
>Polymer push compartment

Water is absorbed into the polymer layer and swells.
This pushes the drug out of the orifice layer.

21
Q

Describe the gellable barrier layer mechanism work.

A

It is when the gell layer around a tablet absorbs water, and the drug diffuses through the gullible barrier

Delayed release occur and a sustained release after the lag

22
Q

How does the erodiable barrier layer work

A

The outer layer absorbs water and is eroded to release the drug.

The drug profile is very step and doesn’t last long

23
Q

What will combined system of swellable-erodabile work

A

Layer 1: is a burst release
Layer 2: Layer will absorp water and either erode or swell.
Then the other half or 2nd drug is released

24
Q

How do tablets that erode work

A

The table core contains a disintegrant

Work by osmotic agent to absorb water till there is high internal pressure.

The coating raptures and the drug is release

Normally coated in ethylcellulose (diffusion arrive ) and eusragit (increase solubility and permeability along GI due to pH)

25
Q

How to tablets that rupture works

A

tablet core contains a disintegrate

osmotic agent absorbing water

internal pressure is too high the coating ruptures releasing the drug

Coated in:
Ethylcellulose: diffusion burrier to retard release

26
Q

How to advanced capsule formulations work

A

Hydrogel composition and wall thickness control water diffusion and delays drug release

Swelling agent absorbs water and pushed the plug out releasing the drug

27
Q

How do advanced pellet formulations work

A

Loaded into a capsule and releases small pellets
-different types of pellets can be placed in on tablet

Provide sigmoidal shape
-mixture of matrix and revivor
Membrane made by:
     >Ethylcellulose 
and 
     >Eudragit: etheric coating 
 increases solubility and permeability as it transits along the GIT tract due to increase in pH giving an increasing rate of drug release  
-This will cause pore to evolve very slowly with increase in solubility of Eudragit
28
Q

How do pH responsive formulations work

A

pH polymer used: change in solubility

Eudargit based on (METH)ACRYLATES

  • Modifiable to different pH sensitivity
  • R group changes
29
Q

What are the different R groups of Methacrylate and what are the affects

A

Methyl co-polymer: Anionic: Gastro resistant

30
Q

Types of colon targeting

A

pH-controlled systems

Time-controlled systems

Pressure-controlled systems

Enzyme-controlled systems

31
Q

pH controlled colon targeting

A

Eudragit soluble at pH 6 or 7 can be used for enteric coating of colon targeted systems

pH =7.5 in the small intestine  can cause early release of drug

Eudragit soluble at pH 7.5 and slowly swelling can be used: in vivo some dosage froms were found not to break down at all

Intra- and inter-individual changes in pH make this systems not reliable

32
Q

time controlled colon targeting

A

Times

-Stomach - 30 mins or 3hrs
SI: 3-5 hrs
Colon:8-15 hrs

33
Q

Pressure controlled colon targeting

A

Muscular contractions in the gastrointestinal tract generate an internal pressure that varies depending on the location

High pressure in the fed stomach could lead to premature drug release

Ethylcellulose capsules of different size and thickness

Pharmaceutical formulation and quality assurance (14 decks)

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