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Ocular Delivery Flashcards

1
Q

What is the anterior segment of the eye?

A

Front

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2
Q

What is the posterior segment of the eye?

A

Back

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3
Q

What is the eye volume?

A

7 µL

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4
Q

What are usual eyedrops doses?

A

20 to 50 µL

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5
Q

Why is there limited uptake of eyedrops?

A

Tear dilution
Short acting
Limited volume of the eye

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6
Q

What percentage of eyedrops are usually absorbed?

A

6.5%

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7
Q

How are posterior segment diseases treated?

A

Intravetreal injection

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8
Q

What eye condition would intavetrial injections be used for?

A

Age Related macular degeneration (avastin)

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9
Q

What are periocular injections?

A

Subconjunctival
Subtenon
Peribublar
Retrobublar

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10
Q

What are the routes can be used to treat eye conditions?

A

Parental – blood aqueous barrier and blood retinal barrier overcome
Oral – limited accessibility to many targeted ocular tissues

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11
Q

What are the six static ocular barriers?

A

Cornea
Sclera
Tear film
Conjunctiva
Vitreos humour
Retina

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12
Q

How does the cornea act as a barrier?

A

It is the outermost transparent layer
Drugs need to be negatively charged but anti-microbials positively charged

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13
Q

How does the sclera act as a ocular barrier?

A

It is structurally supportive
Drug moves through holes in matrix
The matrix is made from mucopolysaccharides and collagen

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14
Q

What gland releases tears and how they spread?

A

Lacrimal gland
Spread via blinking creating a tear film

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15
Q

How thick is the tear film and what is its pH?

A

7 µm thick
PH 7.3 to 7.7

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16
Q

What is the role of the tear film?

A

Remove material from surface of eye (drugs)

17
Q

What layers make up the tear film?

A

External lipid layer
Middle aqueous layer
Adherent mucus layer

18
Q

what is the surface area of the conjunctiva

A

18 cm²

19
Q

What is the function of the conjunctiva?

A

Help form and maintain pre-corneal tear film

20
Q

How does the conjunctiva act as a barrier?

A

It has tight junctions

21
Q

What is the function of the virtuous humour?

A

Shape support of retina and lens

22
Q

How does the retina act as a barrier?

A

The blood retina barrier
Drugs enter choroid but struggle in the retina

23
Q

What are other barriers to ocular delivery other than static barriers?

A

Dynamic ocular – blood and lymphatic system
Metabolic ocular and eflux pumps

24
Q

What are three types of ocular implants?

A

Subconjunctival implant – for anterior segment disease
Intrasceral- both anterior and posterior
Intravetreal- posterior

25
Q

What drug does Ocusert deliver, for how long and for what condition?

A

Pilocarpine, one week, glaucoma

26
Q

How does Ocusert treat glaucoma ?

A

Increases aqueous humour outflow, decreasing intra ocular pressure

27
Q

What kinetics does Ocusert follow?

A

Zero order kinetics, membrane permeation control and depends on excess drug in reservoir

28
Q

What is the mechanism of Ocusert?

A

Water enters through ethylene membrane, dissolves drug

29
Q

What are the advantages of Ocusert?

A

Reduced installations of eyedrops

30
Q

What are two other examples of non-biodegradable ocular implants?

A

Vitrasert- aids Related retinitis. Attached to sclera- side effect is retinal detachment
Retisert- prevents blindness. 30 month delivery ,smaller so smaller incision.

31
Q

What are disadvantages of non-biodegradable implants?

A

Large incisions
Need expert
Cost
Need surchers, or other anchors
Need re-implantation once drug completely released
Side effects include retinal detachment and cataracts

32
Q

What are examples of biodegradable ocular implants?

A

Lacrisert- Made of HPC, treats dry eye by stabilising and thickening the pre-corneal tear film- prolongs tear break up time. Side effects include blurred vision and irritation.
Ozurdex- Dexamethasone for macular Odema, intro, PLGA matrix. Six month delivery.

advanced drug delivery (15 decks)

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