Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Pharmacy Year 2 Semester 2 > Modified release lecture 2/2 - transdermal drug delivery > Flashcards

Modified release lecture 2/2 - transdermal drug delivery Flashcards

1
Q

Describe how to microencapsulate a drug

A

Simply coating (e.g. by spray) the surface of drug particles with polymer to slow down water penetration and hence dissolution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What MR designs can be microencapsulated?

A

e.g. -resinates of strong cationic drugs can be formulated as sustained release suspension, tablets capsules or microparticles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

how do ion exchange resins work?

A

Ionised drug binds to a polymeric (insoluble) resin (usually 1-2mm bead) through opposite chargers -drug-resin then milled to get a smaller particle size -particles then packed into a capsule, tableted or suspended in liquid -can be modified further for use in monolithic, reservoir and microencapsulated type systems

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Release mechanism of ion exchange resins?

A

Simple ion exchange in the GIT where electrolyte concentration being high can change the drug for another counter ion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Example of ion exchange resin

A

nicorette is a nictionine complex with a cation exchanger

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Give an advantage of using ion exchange resins

A

Reduced risk of dose-dumping

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

ion exchange resins… 1) basic drugs (salt form or free base) bind to what exchange resin type? 2)what about acidic drugs?

A

1) cationic exchange resin (resin itself is an anion) 2) anion exchange resin (resin itself is a cation)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe the Continus [10] tablet system from a formulation point of view

A

-API in a mixture of hydrated and hydroxyalkyl cellulose and higher laiphathic alcohol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Mechanism of release for a Continue [10] tablet system?

A

Dissolution of the higher aliphatic alcohol and dissolution of the drug through the hydrated hydroxyalkyl cellose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

For Continus [10] tablet systems, what decides the rate of release?

A

Relative amounts of hydroxyalkyl celluloses and higher aliphatic alcohols plus extent of hydration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe the MST Continus Suspension granules formulation

A

-Morphine bound to ion exchange resin beads -Mesh cationic exchange resin -pink granules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the release mechanism for MST Continus Suspension granules?

A

-Morphine displaced by sodium and potassium ions present throughout the GIT -plasma profile is comparabe to that of the MST CONTINUS tablet -the morphine-free resin is then excreted

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Describe the Zomorph formulation

A

-Zomorph modified release capsules -pellets contained in a capsule shell determines the dose of morphine sulphate -morphine sulfate+binding agent –> spheres - -then coat with ethyl cellulose as a suspension and dry. This coat envelopes each pellet, thickness of the coat determines the release characteristics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Release mechanism for Zomorph MR Capsules?

A

Diffusion of the active material across the ethylcellulose coat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Why should you NOT crush or chew Zomorph capsules/pellets?

A

-crushing or chewing of the pellets will destroy the ethylcellulose coat, therefore will alter the product’s release profile

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Describe the formulation of MXL capsules

A

-powdered morphine + hydrophobic wax (hydrogenated vegetable oil) and cooled to give multi-particulates of diametre 0.25-1.8mm -with evenly distributed drug in wax. These are then encapsulated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Release mechanism of MXL capsules?

A

-capsules disintegration (~15mins) -water enters the multiparticulates and morphine diffuses out of each particle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Why must morphine sulfate extended-release tablets be taken whole? Why is chewing, crushing or dissolving the tablets not allowed?

A

Crushing, chewing or dissolving the morphine extended-release tablets/capsules will result in uncontrolled delivery of morphine and can lead to overdose or death

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Advantages of transdermal drug delivery?

A

-simple and safer administration and termination of therapy -avoids first pass metabolism -near constant therapeutic concentrations over extended time -patient compliance -reduces need for multiple dosing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What are the disadvantages of transdermal drug delivery?

A

-higher product cost -limited drugs which can penetrate skin barriers -need to be potent drugs as the patch size is small

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Imagine a pin goes right through your skin, what layers of skin will it go through, from outside to inside?

A

Epidermis Dermis Subcutaneous fat

22
Q

4 layers of epidermis from outside to inside?

A

Stratum corneum Stratum granulosum Stratum spinosum Stratum basale

23
Q

Stuff in dermis?

A

-sweat ducts -sebaceous glands -arrector pilli muscles -hair follicles

24
Q

stuff in subcutanous tissue?

A

-blood vessels -fat lobules

25
Q

Functions of skin

A

-barrier -support -thermal -cushion -insulation

26
Q

surface pH of skin

A

pH~5

27
Q

Routes for drug to enter skin

A

-Intercellular route -intracellular route -shunt routes

28
Q

Features of dermis

A

-comprises collagen, elastin and polysaccharides -water rich -has blood supply -helps maintain temperature -can remove permeating solutes -has nerve supply -sink conditions for drug absorption

29
Q

Where in the skin is the… 1) Cutaneous microcirculation 2) systemic circulation

A

1) dermis 2) subdermal issue

30
Q

Substances that permeate the stratum corneum well

A

-moderately polar, amphiphillic (logP range 1-5) -unionised -tend to form hydrogen bonds -low molecular weight (<500)

31
Q

examples of drugs that can permeate the stratum corneum

A

Estradiol Fentanyl Nicotine

32
Q

Factors that increase permeation of the stratum corneum

A

-hydration of skin -higher temperature -broken or peeled skin

33
Q

2 General types of TDS

A

-reservoir -matrix

34
Q

Describe the reservoir TDS system

A

-Tighter control but higher risk of dose dumping -release controlled by diffusion through a membrane -in simplest form, space between impervious backing layer and rate-controlling membrane (RCM) provides a reservoir for the drug to be contained -RCM is coated with thin layer of adhesive polymer matrix

35
Q

Describe the matrix TDS

A

release controlled by diffusion through a polymer matrix

36
Q

Discuss the basic components of a patch

A

-drug(s) in polymer matrix or reservoir -penetration enhancers (accelerants) interact with stratum corneum to alter structure -adhesive, pressure sensitive and compatible with drug and all excipients -protective release liner, chemically inert, disposable and usually occlusive to prevent loss of volatiles -outer backing laminate, flexible but good tensile strength

37
Q

example of a TDS penetration enhancer/accelerant

A

Sodium lauryl sulfate

38
Q

Examples of TDS adhesives

A

-polyacrylate -polyisobutylene -polysiloxane

39
Q

Examples of outer backing laminates for TDS

A

-paper, plastic or foil -polyesters -elastomers -ethylene vinyl acetate (EVA) -aluminised plastic laminate

40
Q

What is the TDS design criteria?

A

1) Delivery rate should be constant (and less than permeability of least permeable skin) 2) Adhesive and vehicle have to be non-irritating 3) Vehicle should have necessary physicochemical properties permitting prompt release of drug 4) System should occlude the skin to ensure one-way flux of drug

41
Q

J=(Km D Cv)/L what do these letters stand for?

A

J= permeation rate (flux) D=drug diffusion coefficient Km=vehicle-membrane partition coefficient Cv=drug concentration in the vehicle Cm= Conc of drug in skin Km=Cm/Cv

42
Q

4 ways to maximise transdermal drug delivery?

A

-have drug at its saturation solubility in the vehicle -use a vehicle which modifies the skin barrier (e.g. occlusives, accelerants) -use a vehicle having a low affinity for the drug (enabling the drug to partition into the SC) -Choose a skin site with low thickness

43
Q

Give 3 TDS commercial examples

A

-Butran - Buprenorphine -Nitro-Dur & Transderm Nitro deliver Nitroglycerin -Fentanyl, many brands, mostly matrix-based

44
Q

Describe an adhesive diffusion-controlled transdermal patch

A

Drug directly dispersed in adhesive layer

45
Q

Adhesive characteristics for TDS?

A
  1. Should allow migration of active drug
  2. Should enable the device to adhere to contours and flexible points of the skin (dependent on the size, thickness and flexibility of the device).
  3. Generally contains active drug to act as a quick acting priming dose.
  4. Should enable device to remain on the skin for a specified period of time (from one to several days)
46
Q

Butrans patch

A

The layers are

(1) a beige-colored web backing layer; (2) an adhesive rim without buprenorphine; (3) a separating layer over the buprenorphine-containing adhesive matrix; (4) the buprenorphine containing adhesive matrix; and (5) a peel-off release liner. Before use, the release liner covering the adhesive layer is removed and discarded.

47
Q

matrix-disperson-type TDS patch

example?

A

example:

. Nitro-Dur Patch ; Nitroglycerin as solid dispersion in hydrophilic Polymer matrix

Drug release ∝ patch area ; 500 µg /cm2 /day

48
Q

membrane-moderated TDS patch

A

E.g. Transderm-Nitro Patch ; Treatment of angina

Nitroglycerin as solid dispersion in hydrophilic liquid silicone matrix

Membrane: Porous ethylene vinyl acetate copolymer releases 500 µg nitroglycerine /cm2 /day

49
Q

fentanyl patches

A
  • Fentanyl is soluble in both fat and water; with a low molecular weight and high potency, it is ideal for transdermal delivery.
  • Both reservoir and matrix type designs are available for Fentanyl.
  • Matrix patches are most common

A reservoir patch is no longer available in the UK as open to drug abuse by cutting the patch open

50
Q

other delivery systems not discussed in this lecture series

A
  • Chemically linked to biodegradable polymers
  • Stimuli responsive DDS
  • Nanoparticle drug delivery systems

Pharmacy Year 2 Semester 2 (33 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions