Comprehensive Guide to Ophthalmic Drug Delivery and Eye Anatomy

Opthalamic

______ products are sterile products applied topically to the eye

Exterior structures (precorneal space)

ophthalmic administration is commonly used for inflammation or infection of _______ of the eye

-conjunctivitis

-herpes infection

-allergy

-corneal trauma

-dry eye syndrome

inflammation or infection of exterior structures of the eye include

-space between the cornea and lens

-glaucoma

Ophthalmic administration is commonly used for conditions in the anterior chamber of the eye which includes

high drug concentration

both external and internal condition are best treated by products that maintain a ______ in the precorneal space for a long time

tear turnover

_______ is a barrier to drug delivery for both external and internal indications

tear ducts; puncta

tear turnover is when tears continuously flow into the precorneal space through ______. and tear continuously flow out of the precorneal space through ______

10µL

the precorneal space can hold _____ or liquid

25-50µL

the typical volume of an eye drop is about _____

true

T/F: the amount over 10µL quickly drains out though the puncta to the throat or drips out onto your face

false (speeds up)

T/F: blinking slows down drainage

increases; decreases

tear production _____ and product residence time ______ in response to irritation

-products pH significantly higher or lower than 7.4

- product osmolarity significantly higher or lower than tears

some eye irritants include

cornea

the _____ is the primary barrier to drug delivery for internal indications

6

the outer surface of the cornea is _____ cell layers thick

false (quickly)

T/F: the out surface of the cornea regenerates slowly

true

T/F: the middle layer is a collage matrix with few cells (aqueous gel)

does not regenerate

T/F: the interior layer of the cornea is a single cell layer thick and it regenerates

passively diffuse

drug molecules must _____ through the cornea into the aqueous humor to treat internal condtions.

-drug molecule lipophilicity

-drug molecule charge

-drug concentration in the product

-precorneal residence time

the amount of drug that can diffuse through the cornea depends on

moderate

a ____ logP is need to cross the epithelium, stroma, and endothelium

faster

higher concentration --> ______ diffusion

more diffusion

longer contact with cornea -->

Drug transport across the conjunctiva and sclera are sources of drug loss. Why?

• Capillaries in sclera drain to the systemic circulation

• Drug molecules absorbed across the conjunctiva and sclera do not enter the eye

Ophthalmic products cannot effectively deliver drugs to the posterior chamber (retinal, vitreous humor). Why?

• The iris and lens are barriers to drug transport into the posterior chamber

• Aqueous humor drains to the systemic circulation

• Ophthalmologists must inject or implant a product to deliver drugs to the posterior chamber

how can you enhance ophthalmic drug delivery?

• increasing viscosity of ophthalmic liquids

• choose a gel, suspension, or ointment over a liquid

How does increasing the viscosity of ophthalmic liquids enhance ophthalmic drug delivery?

Higher viscosity slows the rate of drainage through puncta

Why should you choose a gel, suspension, or ointment over a liquid if you want to enhance ophthalmic drug delivery?

• solutions typically have the shortest residence time

Creams are to be used in the eye T/F

false

Creams are not used in the eye. T/F

true

list common solvents in ophthalmic products

• sterile water

• glycerin

• propylene glycol

list common tonicity adjusters in ophthalmic products

• glycerin

• NaCl

• Boric acid

list common viscosity adjuster, gelling agent in ophthalmic products

• carbomer

• cellulose esters (methyl, hydroxyethyl, hydroxypropylmethyl)

• xanthan gum

• polyvinyl alcohol

list common wetting agents in ophthalmic products

• surfacants

• polysorbate 20

• tyloxapol

list common antioxidants in ophthalmic products

• edetate disodium

• sodium sulfite

• sodium metabusulfite

list common buffers in ophthalmic products

• Monosodium phosphate

• disodium phosphate

list common preservatives in ophthalmic products

• benzalkonium chloride

• benzethonium chloride

• chlorobutanol

• sorbic acid

• phenylmercuric nitrate

• thimerosal

list ointment product bases

• petrolatum

• mineral oil

• lanolin