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Jihong Han's lectures > Modified release oral drug delivery > Flashcards

Modified release oral drug delivery Flashcards

1
Q

Why modified release?

A
  • Conventional dosage forms have little control over the delivery of drug, release rate is controlled
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2
Q

An ideal drug delivery system would deliver the drug to the site of action at a desired rate. TRUE OR FALSE?

A

TRUE

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3
Q

What is temporal control?

A

-Delivery drug at constant rate, where therapeutic effect is deirectly linked to steady state plasma concentration

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4
Q

What is spatial control?

A
  • e.g Delivery to the colon or other sites in the GI tract
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5
Q

What is the rationale behind modified release systems?

A

-The basic idea is to alter the pharmacokinetic profile of a drug using delivery dosage forms, so that the PK profile is more of a property of the delivery systems and not solely the inherent property of the drug molecule irself

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6
Q

Drugs in which class are most suitable for modified release dosage forms?

A

Class 1

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7
Q

In order to improve bioavailability drugs in which class would benefit the most from formulation approaches to improve dissolution rate?

A

Class 2

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8
Q

What biological factors affect the product design and performance?

A
  • Absorption rate constant
  • Gastric emptying
  • Transit time in small intestine
  • Colonic tansit time
  • pH and enzymes in the GI tract
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9
Q

What drug properties affect product design and performance?

A
  • Aqueous solubility
  • Partition coefficient logP
  • Drug stability in the physiological environement
  • Biological half life
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10
Q

To maintain a staedy state plasma concentration, the zero order release rate should be directly proportional to the elimination rate. TRUE OR FALSE?

A

TRUE

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11
Q

For drugs with short half life, the elimination rate is significant, therefore, require substantial sustaining supply e.g large sustaining dose. TRUE OR FALSE?

A

TRUE

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12
Q

What features do drugs not suitable for sustained release dosage forms have?

A
  • Half life too long or too short
  • Poor safety margin
  • Large dose
  • Poor solubility
  • Absorption rate is too slow
  • Not uniformily absorbed through out the GI tract
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13
Q

What are some fo the advantages for sustained release dosage forms?

A
  • Reduced dosing frequency
  • Improved patient compliance
  • Reduced fluctuantion in plasma concentration
  • Reduced side effects due to high peak conc
  • Improved action of drug during night time
  • Reduction in GI irritation caused by dose dumping
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14
Q

What are the disadavantages of sustained release dosage forms?

A
  • Potential overdosing due to unexpected dose dumping
  • Not easy to adjust dose regimen
  • More expensive per unit dose than conventional dosage forms
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15
Q

Hydrophilic polymers form a gel layer or viscous layer when in contact with water. TRUE OR FALSE?

A

TRUE

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16
Q

What two factors determine release rate in gel layer?

A
  • Tortuosity

- Microviscosity

17
Q

Give examples of matrix forming materials?

A
  • HPMC

- Hydroxylpropyl cellulose

18
Q

Gel modifiers such as sugars and soluble polymers can modify
-drug release
-rates and extent of the hydration process
-microenvironment in the gel layer
TRUE OR FALSE?

A

TRUE

19
Q

What are some ads of hydrophilic matrix systems?

A
  • Simple
  • Excipients are cheap and generally regarded as safe
  • High drug load capacity
  • No ghost matrix erodible
  • Possible to obtain different profiles of release
20
Q

What are some disads for hydrophilic matrix systems?

A
  • Diffusion is dependent on two diffusion process
  • Erosion makes drug release process complicated
  • Formulation must be thouroughly studied with the right materials chosen
21
Q

Describe the insoluble polymer matrix system?

A
  • Less frequently used
  • Polymers for a matrix in which drug particles are interspersed
  • The polymer matrix remains intact throughout the GI tract
  • Drug molecules diffuse out through the various channels
22
Q

In the insoluble polymer matrix system diffusion rate depends on what?

A
  • Pore size
  • Number of pores
  • Tortuoisity
23
Q

How can fast release insoluble polymers be achieved?

A
  • Polymers with low molecular weight and low viscosity
  • Low percentage of polymers in formulation
  • Incorporation of release modifiers
24
Q

How can slow release insoluble polymers be achieved?

A
  • Viscus polymers
  • Polymers with high molecular weight
  • Polymers with high degree of crosslinking
  • High percentage of polymers in formulation
25
Q

What is membrane controlled systems?

A

-Dosage form covered in a membrane (monolithic form - one big unit or pellet form - many pellets )

26
Q

Describe the osmotic pump system

A
  • Only water molecules diffuse through the membrane
  • Solid contents dissolve and build up osmotic pressure inside
  • Water molecules enter the core due to the difference of osmotic pressure
  • Drug solution pushed out via the orifice and more solid content dissolve
27
Q

What factors affect drug release in osmotic pump systems?

A
  • Type of semipermeable membranes (different membranes may have different k)
  • Area and thickness of the semipermeable membrane
  • Solubility of drug
  • Osmotic pressure
  • Size of orifice which affects the difference of static pressure
28
Q

What is gastroretention?

A

-Helps etain drug in the stomach for longer against stomach emptying

29
Q

What appraoches can be taken to achieve gastroretention?

A
  • Mucoadhesion - mucoadhesive polymers such as chitosan
  • Floating - gas generating agents or lipid can be used
  • Size increasing system (after hydration)
30
Q

In waht circumstances are drugs delivered to the colon?

A
  • Inflammatory bowel disease e.g ulcerative colitis

- Carcinoma of colon

Jihong Han's lectures (11 decks)

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