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Advanced Drug Delivery > Ocular Drug Delivery > Flashcards

Ocular Drug Delivery Flashcards

1
Q

List 8 common ocular diseases

A

Blepharitis
Conjunctivitis
Uveitis
Dry-eye syndrome
Cataract
Diabetic retinopathy
Age-related macular degeneration
Glaucoma

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2
Q

What are the 2 sections of the eye?

A

Posterior
Anterior

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3
Q

What is the number one ocular delivery route?

A

Eye drops

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4
Q

What are the problems with eye drops?

A

Less that 5% of drug is absorbed
Poor patient compliance

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5
Q

What is an intravitreal Injection?

A

Injection directly into the vitreous humour

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6
Q

What are intravitreal injections used to treat?

A

Posterior segment eye diseases

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7
Q

Why do intravitreal drug injections not reach the retina?

A

Because of the inner limiting membrane
Separates the retina from the vitreous humour

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8
Q

What is a periocular injection?

A

Injection to the outer surface of the eye

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9
Q

List the types of periocular injections?

A

Peribulbar
Retrobulbar
Subtenon
Subconjunctival

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10
Q

What happens following periocular injection?

A

Drug diffuses across the sclera

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11
Q

Why do periocular injections have low bioavailability?

A

Due to :
Diffusion through sclera
Systemic clearance
Loss of drug before reaching target tissue

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12
Q

What type of ocular injections can be used to get drug to the retina?

A

Periocular injections

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13
Q

List some molecules that can be delivered by periocular injection

A

Corticosteroids
Immunoglobulins
DNA
Antisense oligonucleotides

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14
Q

What are the 5 main routes of ocular drug delivery?

A

Topical
Parenteral
Oral administration
Intravitreal
Periocular

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15
Q

What are the challenges with topical ocular drug delivery?

A

Poor uptake
Tear dilution
Short-acting

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16
Q

What are the challenges with parenteral ocular drug delivery?

A

Blood-aqueous barrier
Blood-retinal barrier

17
Q

What are the challenges with oral ocular drug delivery?

A

Limited access to target ocular tissue with oral route
High doses would be required (side effects)

18
Q

What are the challenges with periocular and intravitreal ocular drug delivery?

A

Poor patient compliance
Have to be given by specialist
However these are used to over come issues with topical/systemic dosing

19
Q

What tissues are barriers to ocular drug delivery? (6)

A

Cornea
Sclera
Tear film
Conjunctiva
Vitreous humour
Blood-retinal barrier

20
Q

How does the cornea act as a barrier to drug delivery?

A

Provides mechanical and chemical barrier
Negatively charged
Drug properties affect permeation rate through the cornea

21
Q

How does the sclera act as a barrier to drug delivery?

A

Has a thick matrix of mucoploysaccarides and collagen
Drugs have to diffuse through holes in the matrix

22
Q

How does the tear film act as a barrier to drug delivery?

A

The tear film acts to remove material from the surface of the eye
This would interrupt drug delivery

23
Q

How does the conjunctiva act as a barrier to drug delivery

A

Tight junctions in conjunctival epithelium
Main barrier for drug penetration across the conjunctiva

24
Q

How does the vitreous humour act as a barrier to drug delivery?

A

Gel structure - water,collagen & hyaluronate
Viscous
Delays the diffusion of drugs across vitreous humour

25
Q

How does the blood-retinal barrier act as a barrier to drug delivery?

A

BRB restricts entry of drugs from the choroid to the retina

26
Q

Name 3 non-biodegradable implants

A

Ocusert
Prosert
Vitrasert

27
Q

Name 3 biodegradable implants

A

Lacrisert
Ozurdex
Sclera plugs

28
Q

What are the advantages of ocular drug delivery? (Implants)

A
  1. Deliver constant therapeutic levels at site of action
  2. Bypass the blood brain barrier
  3. Release rates are below toxic levels
  4. High drug concentrations without systemic side effects
29
Q

What type of implants are used to treat anterior-segment diseases?

A

Subconjunctival, intrascleral & transcleral

30
Q

What type of implants are used to treat posterior-segment diseases?

A

Intravitreal, suprachoroidal, intrascleral & transcleral

31
Q

What is Ocusert?

A

Membrane-controlled reservoir system for the treatment of glaucoma

32
Q

What is the active agent in Ocusert?

A

Pilocarpine

33
Q

Describe the design of Ocusert (PPQ)

A

Membrane Permeation-Controlled Drug delivery
Drug reservoir encapsulated in a rate controlling polymeric membrane

34
Q

Describe the operation of Ocusert (PPQ)

A

Water penetrates the system and dissolves the drug
This will form a saturated soloiution
Saturated solution maintains constant release
Movement of drug is driven by diffusion
Follows zero order kinetics

35
Q

Describe the Pilo-20 ocular therapeutic system

A

Release rate of 20ug/hour
For 7 days
5mg of pilocarpine in reservoir

36
Q

List the advantages of Ocusert

A

More efficient use of pilocarpine
Reduces the number of instillations required
Higher drug concentration obtain than with eye drops

37
Q

List the disadvantages of non-biodegrade implants

A

Retinal detachment
Vitreous haemorrhage
Requires retina specialist for administration
Requires antimicrobial eye drops after insertion

38
Q

What is Ozurdex?

A

Biodegradable vitreous implant
Used to treat macular Edema

39
Q

What is the active ingredient in Ozurdex and how long is it released for?

A

Dexamethsone
6 months

Advanced Drug Delivery (18 decks)

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