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PHARM 124 > MRDF > Flashcards

MRDF Flashcards

1
Q

Based on the conventional release profile, what are the challenges you identify for drug action?

A

conventional dosage forms do not maintain blood concentration within therapeutic range for extended period of time and
controllable drug release is not possible

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2
Q

What does MEC?

A

minium effective concentration

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3
Q

What is MTC?

A

Minimum toxic concentration

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4
Q

if drug level have to be maintained using conventional dosage forms what are the two approaches?

A

increase initial dose to increase duration of actions
administer the drug repeatedly using a constant dosing interval

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5
Q

What is the consequence of increasing initial dose?

A

increase potential of toxicity

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6
Q

What is the consequence of repeated drug administration

A

missed doses or
made up doses or
pt non-compliance

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7
Q

What is the rationale for MRDFs?

A

to prolong or control drug availability or release with the intent of improving efficacy of drug therapy

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8
Q

What is the two major types of MRDFs?

A

delayed action
extended action

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9
Q

Define delayed action

A

lag period between admin. and release
release the drug at particular site
mostly enteric coated

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10
Q

Define extended action

A

release the medication in a controlled manner at a predetermined rate, duration and location to achieve and maintain therapeutic blood levels

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11
Q

What does sustained release systems include?

A

any drug delivery system that achieves slow release of drug over extended period of time

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12
Q

What is needed to consider it a controlled release system?

A

if a sustained release system is successful at maintaining constant drug levels in the target organs

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13
Q

What is needed to consider it a prolonged release system?

A

prolongs therapeutic levels of the drugs

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14
Q

What is the purpose of extended release systems?

A

allows reduction in dosing frequency

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15
Q

What is the purpose of delayed release systems?

A

it can release the drug at a time other than promptly after administration

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16
Q

Define targeted release

A

isolates or contrates the drugs in specific body region, tissue or organ

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17
Q

What is an example of targeted release?

A

tumor nanomedicine - targeted drug delivery

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18
Q

what is repeat action?

A

forms usually contain two or more single doses of the drug, one for immediate release and the second for delayed release

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19
Q

What are the examples for preparing delayed action formulation?

A

entric coated
rheumatoid action
morning sickness

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20
Q

What is the rationale for extended release?

A

provides an immediate release, giving the effect now as well as by the gradual and continual release of additional amounts of drug

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21
Q

T/F Controlled release are therefore extended release formulations

A

True

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22
Q

What is the difference between SR and XL?

A

it is different in the duration of action

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23
Q

List somes advantages of MRDFs

A

less fluctuation of drug levels
reduced dosing frequency
enhanced pt compliance
reduction in A/E
reduced in health care cost

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24
Q

List some limitations of MDFS

A

costly
immediate termination of drug action is not possible
contains higher drug amounts (abuse potential)
drug excipient interaction
more complicated formulation design
not suitable for rapid action (Emergency use)
not flexible (cannot split)

25
To have the equvient dose how many doses in the day with IR, SR and XR
IR - TID SR - BID XR - Once daily
26
List the variables in the design
route of delivery type of delivery system disease being treated the patient length of therapy properties of the drug (physicochem/bio)
27
What factors are considered when the drug has low water solubility?
longer time to dissolve in GI fluids slower absorption inherently extended release
28
What factors are considered when the drug has high water solubility?
difficult to reduce their dissolution rate to an acceptable range
29
Define partition coefficient
potential of drugs to cross biological membrane
30
What does partition coefficient affect?
the ability of the drugs to diffuse through the polymers used in the design of MRDFs
31
What two factors need to be balanced with stability>
the stability of the drug inside and outside of the body
32
Explain the slow kinetics
inherently long acting not necessary to prepare MRDFs
33
Explain the fast kinetics
very short half lives very large amounts will be required to design MRDF
34
What are the two factors need to look at for rate of absorption and excretion?
slow kinetics or fast kinetics
35
Explain the ability of drugs for complexation
drugs which show high levels of protein binding in the blood are not suitable for MRDFs
36
T/F Only free unbound drugs can diffuse through tissues and hence can be controlled
True
37
What needs to be looked at for a good margin of safety?
therapeutic window --> it can not be narrow as it has a risk of dose dumping if the product is defective or incorrectly administered
38
Should MRDFs be used for chronic conditions or acute? Why?
acute --> as more dosage adjustments are required and immediate use of the medications
39
What should be considered for dosing for MRDFs?
If conventional formulation has a large dose  larger sized tablets and capsules required to design MRDFs difficult swallowing  reduced patient compliance
40
What is the max dose for oral formations?
0.5-1 gram
41
List the mechanisms for modified release
membrane dissolution membrane diffusion matrix dissolution matrix diffusion membrane-matrix hybrids osmotic pressure
42
What categories do most products fall into?
membrane dissolution systems matrix dissolution systems
43
Define dissolution systems
Controlled release products are prepared by controlling the dissolution rate of drugs that are readily soluble.
44
T/F uncoated particles = immediate release form of drugs
True
45
Explain the two types of membrane dissolution systems
different groups of particles with different membrane thickness and composition are made, that will release the drug at different rates or times. a layer of drug is coated by sugar core then coated with slowly dissolving membrane another layer of drug that another coat (the outer layer is the loading dose)
46
Explain Layered tablets
Layered technology Immediate burst and prolonged release  layered dissolution
47
Explain matrix dissolution systems
drug is dispersed in a series of different size granules the different size will have different dissolution times
48
What are two types of diffusion systems?
membrane diffusion matrix diffusion
49
Explain diffusion systems
release rate of drug is determined by its diffusion through a water insoluble polymer
50
Explain membrane diffusion
core is surrounded by a polymeric membrane reservoir devices
51
Explain matrix diffusion
drugs is distributed uniformly in an inert polymeric matrix matrix device
52
Explain how reservoir devices
drug release usually involves - dissolution of drug inside the reservoir - diffusion of drug across membrane - rate controlling step
53
What is the rate limiting step with matrix diffusion devices?
diffusion of the drug from the matrix to outside
54
Explain how a matrix diffusion device works
drug is dispersed homogeneously in the matrix which does not dissolve or erode
55
What are some examples of membrane-matrix hybrid?
mirena IUD nuva ring
56
Define osmotic systems
it uses osmotic pressure can be employed as the driving force to generate a constant release of drug, provided that constant osmotic pressure is maintained
57
Explain how osmotic pressure works to help with MDRFs
Water moves in --> dissolves or suspends the drug --> membrane is not permeable to the drug --> the system pushes the drug out through the orifice
58
What are some counselling points for MRDFs?
- Advise the patients of the dose and dosing frequency of modified drug release products - Advice the patients not to use them interchangeably with immediate release of the same drug - Patients stabilized on a modified-release product should not be changed to an immediate release product - Once stabilized, patients should not be changed to another extended-release product unless there is assurance of equivalent bioavailability. - capsules should not be crushed or chewed - pt fed by an NG feeding tube may receive conventional or modified release - empty shells may be seen in the stool

PHARM 124 (14 decks)

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