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PHAR124 > Modified Release Dosage Forms > Flashcards

Modified Release Dosage Forms Flashcards

1
Q

Explain the blood concentration curve.

A
  1. drug conc. in blood begins at zero–>all drug is still in dosage form
  2. conc. begins to rise–>no effect yet
  3. conc. crosses minimum effective conc–>therapeutic effect
  4. conc. is at its peak–>maximum therapeutic effect/minimum toxic conc.
  5. conc. starts to decline–>reduced therapeutic activity
  6. conc. falls below MEC–>drug elimination, no therapeutic activity
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2
Q

What is the definition of the following?
toxic concentration
therapeutic window
onset of action

A

toxic concentration: onset of adverse effects
therapeutic window: concentration between MEC and MTC
onset of action: time at which MEC is reached

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3
Q

What are the challenges of the conventional dosage forms?

A

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

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4
Q

What are the approaches if drug levels have to be maintained using conventional dosage forms?

A

increase initial dose to increase duration of action:
-challenge: blood conc will rise, earlier MTC and to a greater extent
-final consequence: increased potential of toxicity
administer repeatedly using a constant dosing interval:
-mainstay of conventional regimen
-challenge: patient inconvenience
-final consequence: missed doses or made-up doses or non adherence

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5
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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6
Q

Differentiate between delayed action and extended action.

A

delayed action:
-lag period between admin and release
-release of drug at particular site
-mostly enteric coated
extended action
-release the med in a controlled manner at a pre-determined
rate, duration and location to achieve and maintain levels

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7
Q

What are sustained-release systems?

A

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

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8
Q

When does a sustained-release system become considered a controlled-released system?

A

if the sustained-released system is successful at maintaining constant drug levels in the target organ

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9
Q

When does a sustained-release system become considered a prolonged-released system?

A

if the sustained-release system prolongs the therapeutic levels of the drug

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10
Q

What are extended release systems?

A

allow reduction in dosing frequency from that necessitated by a conventional dosage form

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11
Q

What are delayed release systems?

A

release the drugs at a time other than promptly after administration
the delay may be influenced by pH

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12
Q

What is targeted release?

A

isolates or concentrates the drugs in a specific boy region, tissue, or organ

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13
Q

What are repeated action forms?

A

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

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14
Q

What is the rationale for extended release formulation?

A

XL products provide an immediate release of drug, which promptly produces the desired therapeutic effect, which is then followed by a gradual and continual release of drug to maintain effect over time
eliminates the need for night dosing

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15
Q

Where does the difference lie when a drug is available in both SR and XL formulation?

A

duration of action
ex: Wellbutrin (bupropion)

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16
Q

True or false: the terms controlled release, sustained release, and extended release are used interchangeably

A

true

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17
Q

What are the advantages of MRDFs?

A

less fluctuation of drug levels
-controlling rate of release eliminates peaks and valleys
reduced dosing frequency
-extended release delivers more than one single dose, usually
taken OD or BID
enhanced patient compliance
-less missed dose, neglected dose, etc
reduction in adverse side effects
-fewer blood level peaks outside therapeutic range
reduction in health care costs
-initial costs are greater but overall treatment cost may be less

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18
Q

What are the limitations of MRDFs?

A

initially they are costly for patients
immediate termination of drug action is not possible
usually contain higher drug amount than in conventional dosing–>abuse potential
higher probability for drug-excipient interaction
more complicated formulation design
not suitable when rapid action is required like breakthrough pain or anxiety attacks
not flexible

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19
Q

True or false: MRDFs can be split

A

false

20
Q

What are the variables on the design of MRDFs?

A

route of delivery
type of delivery system
disease being treated
the patient
length of therapy
properties of the drug (physicochemical, biological)

21
Q

Which solubility is preferred for MRDFs?

A

medium solubility
no need for MRDFs for low water solubility

22
Q

What solubility is it not possible to make MRDFs?

A

<0.01mg/mL solubility
-difficult diffusion through layers of polymer

23
Q

What is the difficulty of using very high water solubility drugs for MRDFs?

A

difficult to reduce their dissolution rate to an acceptable range

24
Q

What is the partition coefficient?

A

potential of drugs to cross biological membrane (ratio of drug in lipid phase vs aqueous phase)
-affects the ability of drugs to diffuse through polymers used in
the design of MRDFs

25
Q

What is the importance of stability for MRDFs?

A

stability of drug in the dosage form outside the body
stability of the drug in the dosage form inside the body
-drugs remain in the dosage form for extended times
-drug is trapped in the system–>penetrating fluids should not
degrade the drug

26
Q

What should be the rate of absorption and excretion for MRDFs?

A

not very slow neither very fast
slow kinetics–>inherently long-acting–>not necessary to prepare MRDFs
fast kinetics–>very short half-lives (<2hrs)–>very large amounts will be required to design MRDFs

27
Q

Regarding complexation, which types of drugs are not suitable for MRDFs?

A

drugs which show high levels of protein binding in the blood
only free unbound drug can diffuse through tissues and hence can be controlled

28
Q

What is an undesired margin of safety for MRDFs?

A

narrow therapeutic window

29
Q

Are MRDFs for acute conditions?

A

acute conditions–>immediate release is required
more dosage adjustments, MRDFs are difficult for dosage adjustments

30
Q

What is the maximum dose for MRDFs?

A

0.5-1g

31
Q

True or false: MRDFs are intended to minimize dosing frequency, thus contains a greater amount of drug than a corresponding single conventional dose

A

true

32
Q

How do we determine the dose size of MRDFs?

A

consider dose of drug in conventional form to determine amount required in SR products

33
Q

What are the mechanisms for modified release?

A

membrane dissolution
membrane diffusion
matrix dissolution
matrix diffusion
membrane-matrix hybrids
osmotic pressure

34
Q

What are dissolution systems?

A

controlled release products are prepared by controlling the the dissolution rate of drugs that are readily soluble
-two categories: membrane or matrix

35
Q

Describe membrane dissolution systems.

A

different groups of particles with different membrane thickness and composition are made, that will release the drug at different rates
-more uniform blood level of drug can be obtained
another type is a layer of drug is coated on a sugar core and then coated with the slowly dissolving membrane material
-another layer of the drug is applied, followed by another coat
-the outer most layer is typically a layer of drug that will serve
as a loading dose

36
Q

True or false: uncoated particles can be used for MRDFs

A

false
uncoated particles=immediate release form of drug

37
Q

What is Spansule technology?

A

capsule filled with granules
-initial dose is promptly released and remaining medication is
released gradually over a prolonged period of time

38
Q

Describe matrix dissolution systems.

A

drug is dispersed in a series of different sized granules made of the matrix material
-different size granules will have different dissolution times
-matrix granules often combined with granules with no matrix
material=providing a loading dose

39
Q

How are matrix dissolution systems prepared?

A

compressing the drug with a slowly soluble polymer carrier (hydrophilic cellulose polymers) into a tablet form
release process: hydration of the cellulose polymer; gel formation on the polymers surface; tablet erosion; subsequent release of drug

40
Q

What are diffusion systems?

A

release rate of drug is determined by its diffusion through a water-insoluble polymer
two types:
-membrane (core is surrounded by a polymeric membrane)
-matrix (drug is distributed uniformly in an inert polymeric matrix)

41
Q

What is usually involved in the drug release of reservoir devices?

A

dissolution of drug inside the reservoir
diffusion of drug across membrane (rate controlling step)

42
Q

Describe matrix diffusion devices.

A

drug is dispersed homogenously in the matrix which does not dissolve or erode
diffusion of the drug from the matrix to outside–>rate limiting step
matrix devices can be excreted in the feces

43
Q

What are membrane-matrix hybrids used for?

A

used mainly for non-oral routes
-NuvaRing
-Mirena IUD
for much prolonged delivery times

44
Q

What are osmotic systems?

A

osmotic pressure can be employed as the driving force to generate a constant release of drug, provided that constant osmotic pressure is maintained

45
Q

How do osmotic pressure systems work?

A

water moves in–>dissolves or suspends the drug–>membrane is not permeable to the drug–>the system pushes the drug out through the orifice

46
Q

What are points to discuss about MRDFs during patient counseling?

A

advise of the dose and dosing frequency of MRDFs
not to use them interchangeably or concomitantly with IR of the same drug
patient should not be changed back to IR without consideration of any existing blood levels of the drug
once stabilized, patients should not be changed to another XL product unless there is assurance of equivalent bioavailability
dont chew or crush
patients fed by an NG feeding tube may receive conventional or modified release
nonerodible plastic matrix shells and osmotic tablets remain intact throughout the GI transit and the empty shells from osmotic tablets may be seen in the stool

PHAR124 (12 decks)

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