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PHARM 125 Midterm 1 > Modified Release > Flashcards

Modified Release Flashcards

1
Q

What are considered USP interchangeable with extended release?
Define them

A

Controlled release:
- release drug at a constant rate and plasma concentrations remain constant

Prolonged release
- drug is provided for absorption over a long period of time; onset is delayed (initial dose + replenishment)

Sustained release:
- an initial release of drug sufficient to provide a therapeutic effect followed by a gradual release of the drug (maintenance dose)

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2
Q

advantages of modified release

A
  • Reduced dosing frequency and decreased accumulation of drugs in body
  • less fluctuation at plasma drug levels
  • Reduced GI side effects
  • Improved efficacy/safety ratio
  • may reduce cost
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3
Q

Disadvantages of modified release

A
  • dose dumping
  • may become lodged in the GI tract
  • additional patient education
  • variable physiological factors (pH differences, GI motility)
  • removal of the drug from system may be hard
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4
Q

What dose size make it difficult for extended release products?

A

500mg+

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5
Q

What are drugs more prone to when they stay longer in the GI tract?

A

to undergo acid-base hydrolysis and enzymatic biotransformation

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6
Q

What occurs to API solubility when it is low vs high

A

Low aqueous solubility (0.1mg/mL or less)
- not suitable to diffuse through a membrane

High aqueous solubility
- rapid dissolution
- difficult to decrease the rate, to modify absorption

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7
Q

What is the ideal Log K value for extended release candidates

A

Log K between 1-3

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8
Q

What does API half-life refer to? what is ideal half life?

A

describes the rate of drug elimination
- ideal between 2-8h

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9
Q

What are the physiochemical factors that can affect modified release drugs

A
  • Dose size
  • Drug stability in the GI
  • API solubility
  • Partition coefficient
  • API half-life
  • Polymer structure
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10
Q

What is the most absorptive region in the GI tract

A

Small intestine

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11
Q

What are the biopharmaceutical factors that can affect modified release drugs?

A
  • anatomical factors of the GI
  • Dietary Factors
  • Physiological Factors
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12
Q

What are safety and risk management factors for dose-dumping

A
  • integrity of dosage form
  • Must have a robust formulation
  • problematic with highly potent drugs with narrow therapeutic index
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13
Q

Explain zero-order kinetics
Equation

A

Drug release is INDEPENDENT of amount of drug in dosage form and is constant over time

Equation (sum of exponents = 0)
- no concentration dependence
- same amount of drug release/unit of time

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14
Q

Explain First order kinetics
Equation

A

Most extended release drugs
- release is DEPENDENT on the amount of drug remaining in the dosage form
- as amount of drug drops, release rate also drops

Equation (sum of exponents = 1)
- concentration dependence

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15
Q

What are the units of reaction rate

A
  • mol/(L s)
  • negative sign
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16
Q

What are the types of modified release systems (5)

A
  • Diffusion controlled (reservoir + matrix)
  • Osmotically controlled
  • Ion-exchange resin
  • Gastric retentive systems
  • Colonic oral delivery system (pH-controlled)
17
Q

Explain reservoir diffusion system

A
  • drug is in a reservoir surround by INSOLUBLE polymeric membrane
  • can be monolithic or multiparticulate
  • rate governed by Fick’s law
  • can be prepared by fluidized-bed coating, rotary granulation, solvent free coating
18
Q

What are advantages of multiparticulates

A
  • minimized risk of dose dumping
  • more consistent in vivo performance
  • tailored released kinetics
19
Q

What are components of a reservoir system in the core and coating

A

Core
- Active drug
- filler
- lubricant/glidant

Coating
- Membrane polymer: HPC, ethyl cellulose, polyvinyl acetate
- Pore former: PEG
- Plasticizer
- Colour/opacifier

20
Q

Explain matrix diffusion systems in genera

A

Consists of drug dispersed homogenously throughout an inert insoluble or swellable/erodible polymer (the matrix)
- no coating
- monolithic only
- most common Extended Release products

21
Q

Explain hydrophilic or swellable matrix systems

A
  • mixed with hydrophilic gel-forming polymer (HPMC, methylcellulose, acrylic copolymers)
  • controlled by diffusion of the drug out the gel layer
  • zero or first order
  • cost effective
22
Q

Explain erosion-controlled matrix systems

A
  • drug release rate controlled by erosion of a matrix in which the drug is dispersed or dissolved it
  • can also be called hydrophilic matrix systems
  • bioerodible matrices: copolymers of lactic and glycolic acid, lipids, waxes
23
Q

Explain inert polymer matrix systems

A
  • first order release, porous matrix
  • hydrophobic matrices: ethylcellulose, carnuba wax (lipid based) - it can include PEG (pore-forming)
24
Q

What are formulation factors that can affect the release rate of matrix diffusion systems? (4)

A
  • Amount of drug in matrix
  • the porosity of the release unit
  • the length of the pores in release unit
  • the solubility of the drug
25
Q

Explain osmotic pressure and osmotically controlled systems

A

Osmotic pressure: pressure applied by a solution to prevent the inward flow of water across a semi-permeable membrane

  • water diffuses in, increase of osmotic pressure forcing drug out through a laser-drill hole
  • zero order release
26
Q

What are the 2 types of osmotic controlled systems

A

Elemental osmotic pump
- single-layer tablet

Push-pull osmotic pump
- bilayer tablet

27
Q

What are the semi-permeable membrane made from in osmotic controlled system

A

from cellulose acetate & PEG

28
Q

Explain ion-exchange resins

A
  • insoluble copolymers matrix containing ionizable groups capable of exchanging ions.
  • reversible
  • resin + drugs are prepared in form of beads or pellets
29
Q

What functional groups are in these types of resins
- strong CATion IERs
- weak CATion IERs
- strong ANion IERs
- weak ANion IERs

A

strong CATion IERs: sulphonic acid

weak CATion IERs: carboxylic acid

strong ANion IERs: trimethyl ammonium chloride

weak ANion IERs: ammonium chloride or primary amine

30
Q

Gastric retentive systems works for retention of DF in the stomach for drugs that have?

A
  • have narrow absorption window
  • act locally in stomach
  • Are unstable in the colon
  • Have low solubility at high pH
31
Q

Advantages of gastric retentive systems (3)

A
  • reduce variability of drug release
  • Local delivery and action
  • Enhanced bioavailability
32
Q

Explain oral colonic pH controlled systems
Example of polymers?

A
  • change in pH results in swelling or de-swelling of polymer

Ex.
- HPMC phthalate
- poly (methylmethacrylate) (Eudragit)

PHARM 125 Midterm 1 (6 decks)

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