Ocular Drug Delivery

Question 1

List 8 common ocular diseases

Answer 1

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

Question 2

What are the 2 sections of the eye?

Answer 2

Posterior
Anterior

Question 3

What is the number one ocular delivery route?

Answer 3

Eye drops

Question 4

What are the problems with eye drops?

Answer 4

Less that 5% of drug is absorbed
Poor patient compliance

Question 5

What is an intravitreal Injection?

Answer 5

Injection directly into the vitreous humour

Question 6

What are intravitreal injections used to treat?

Answer 6

Posterior segment eye diseases

Question 7

Why do intravitreal drug injections not reach the retina?

Answer 7

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

Question 8

What is a periocular injection?

Answer 8

Injection to the outer surface of the eye

Question 9

List the types of periocular injections?

Answer 9

Peribulbar
Retrobulbar
Subtenon
Subconjunctival

Question 10

What happens following periocular injection?

Answer 10

Drug diffuses across the sclera

Question 11

Why do periocular injections have low bioavailability?

Answer 11

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

Question 12

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

Answer 12

Periocular injections

Question 13

List some molecules that can be delivered by periocular injection

Answer 13

Corticosteroids
Immunoglobulins
DNA
Antisense oligonucleotides

Question 14

What are the 5 main routes of ocular drug delivery?

Answer 14

Topical
Parenteral
Oral administration
Intravitreal
Periocular

Question 15

What are the challenges with topical ocular drug delivery?

Answer 15

Poor uptake
Tear dilution
Short-acting

Question 16

What are the challenges with parenteral ocular drug delivery?

Answer 16

Blood-aqueous barrier
Blood-retinal barrier

Question 17

What are the challenges with oral ocular drug delivery?

Answer 17

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

Question 18

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

Answer 18

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

Question 19

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

Answer 19

Cornea
Sclera
Tear film
Conjunctiva
Vitreous humour
Blood-retinal barrier

Question 20

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

Answer 20

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

Question 21

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

Answer 21

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

Question 22

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

Answer 22

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

Question 23

How does the conjunctiva act as a barrier to drug delivery

Answer 23

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

Question 24

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

Answer 24

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

Question 25

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

Answer 25

BRB restricts entry of drugs from the choroid to the retina

Question 26

Name 3 non-biodegradable implants

Answer 26

Ocusert Prosert Vitrasert

Question 27

Name 3 biodegradable implants

Answer 27

Lacrisert Ozurdex Sclera plugs

Question 28

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

Answer 28

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

Question 29

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

Answer 29

Subconjunctival, intrascleral & transcleral

Question 30

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

Answer 30

Intravitreal, suprachoroidal, intrascleral & transcleral

Question 31

What is Ocusert?

Answer 31

Membrane-controlled reservoir system for the treatment of glaucoma

Question 32

What is the active agent in Ocusert?

Answer 32

Pilocarpine

Question 33

Describe the design of Ocusert (PPQ)

Answer 33

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

Question 34

Describe the operation of Ocusert (PPQ)

Answer 34

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

Question 35

Describe the Pilo-20 ocular therapeutic system

Answer 35

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

Question 36

List the advantages of Ocusert

Answer 36

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

Question 37

List the disadvantages of non-biodegrade implants

Answer 37

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

Question 38

What is Ozurdex?

Answer 38

Biodegradable vitreous implant Used to treat macular Edema

Question 39

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

Answer 39

Dexamethsone 6 months