Ocular drug delivery Flashcards
(18 cards)
What are the two segments into the eye and how do they factor into drug delivery?
The anterior & posterior.
Anterior can be accessed topically but the posterior can only be accessed via invasive techniques (injections)
What are symptoms and causes of cataracts - 2
Portion of the lens hardens and becomes cloudy, can be annoying to painful.
Some causes are age, injury, previous surgery or certain medications.
Outline the treatment of a cataract
Surgery - replacement of the lens with a plastic lens.
or
1. Phacoemulsification: ultrasound tip to break down cataract
2. Removal of debris
3. Lens implantation into capsule
Describe two posterior eye segment diseases.
Age-related macular degeneration (AMD): Degeneration of the central part of the retina causing a loss of focus - can cause excess blood vessel proliferation. It is irreversible but symptoms can be managed.
Central Serous Retinopathy (CSR) - Disorder of the outer blood-retinal barrier. Fluid build-up under the retina. Can use laser based therapy.
Glaucoma, causes & symptoms - 5
- Progressive neuropathy (optic nerve damage)
- Fluid build-up changes intraocular pressure above normal range (>21 mmHg)
- Loss of retinal nerve fibre layer, thinning of neuro-retinal rim & irreversible peripheral vision loss.
- Headaches, nausea, haloes around light or asymptomatic until later stages
- Causes: age, ethnicity, genetic profile, other underlying diseases
3 types of glaucoma
Primary open angle glaucoma: slow build-up of fluid caused by blockages
Acute angle closure glaucoma: sudden fluid build-up caused by blockages
Secondary glaucoma: existing underlying eye condition (e.g., uveitis)
What barriers are there to ocular drug delivery - 5
- Conjunctiva: clear mucus membrane covering part of eye & eyelids
- Cornea: protective envelope over iris & pupil
- Lacrimal fluid: tears (and blinking!)
- Difficult to deliver such small volumes via eye drops
- Drainage into nasal cavity (loss of drug)
What is the conjunctiva?
Thin, transparent mucus epithelial layer covering inside of eyelids and part of eyeball (anterior)
What do drugs delivered to the cornea require?
Lipophilic properties as it is lipid-rich, avascular & negatively charged
What anatomical barriers are there to topical formulations in the eye - 4
- Layers of cornea (need amphipathic formulation)
- Conjunctival capillaries & lymphatics (drug loss into systemic system)
- Conjunctival epithelial tight junctions
- Scleral matrix of fibres and proteins (overall, negatively charged which could affect drug permeability)
Why is reaching the intraocular tissue difficult?
Most drugs washed away within minutes due to natural clearing process.
What role do ointments play in the eye - 4
- Helps to sustain drug release & improves BA
- Viscosity of formulation an issue: Greasiness/blurred vision caused by thicker formulation (better overnight)
- Prolonged exposure & repeated blinking can lead to irritation/ inflammation
- Systemic complications with chronic administration
Periocular delivery - 3
- Around the eyeball (but within the orbit)
- Transscleral pathway; systemic circulation through the choroid; or through the tear film, cornea, aqueous humour, and the vitreous humour
- Still various barriers to contend with - Drainage an issue in some strategies
Outline intravitreal delivery - 3
- Distribution is non-uniform
- Particle size matters (small easily distributed, large not so much)
- Chemistry & MW of formulation matters (vitreous component interaction)
What are the advantages and disadvantages of the periocular and intravitreal routes?
Overcomes issues with topical formulations & drug delivery to posterior segment
Periocular route less invasive than intravitreal route
Low patient compliance
What is Iluvien - 5
- Fluocinolone acetonide (corticosteroid) implant for Chronic Diabetic Macular Oedema (DMO)
- Reduce VEGF (a protein that increases vascular permeability & causes oedema)
- Intravitreal injection
- Implant sits in vitreous fluid
- can release drug for up to 36 months
What is Lucentis - 4
- Treatment for chronic diabetic macular oedema (DMO) and neovascular (wet) age- related macular degeneration (AMD)
- contains ranibizumab (humanised monoclonal antibody fragment produced in E. coli cells by recombinant DNA technology)
- Intravitreal injection
- Reduces abnormal blood vessel growth (anti-VEGF)
What is dextenza - 4
- Inflammation following surgery (e.g., cataract) or persistent itching associated with allergic conjunctivitis
- Active ingredient: dexamethasone
- Hydrogel-based implant acts as a plug into tear duct
- Degrades over time
