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Drug Delivery 2 > Ophthalmic > Flashcards

Ophthalmic Flashcards

1
Q

Delivery routes to the eye

A

Topical
Intravitreal
Subconjunctival
Subchordial
Suprachordial

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2
Q

Topical ocular delivery goals

A

Target the site of action
Prolong residence time
Decrease frequency
Improve patient compliance

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3
Q

Eye drop advantages

A

Each access and localized effect
Avoid 1st pass metabolism and system side effects

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4
Q

Eye drop disadvantages

A

Efficient clearance mechanisms
Hood-occupation barriers
Posterior eye diseases harder to treat

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5
Q

Barriers to topical drug delivery

A

Cornea—major barrier
Iris—melanin binds drugs
Tear duct—nasolacrimal clearance
Conjunctiva—vascular, increased clearance
Ciliary body—produces aqueous humor

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6
Q

Cornea as a barrier

A

Epithelium—lipophilic
Stroma—hydrophilic

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7
Q

The tear film

A

Lipid belayer—protective
Aqueous layer—anti-bacterial
Mucus layer—adherence
Protein composition influences viscosity
Blinking replaces tear film
Irritating drugs stimulate reflex blinking and faster elimination

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8
Q

Nasolacrimal drainage

A

Every time you blink drugs are cleared with tears and sent to the nasal cavity

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9
Q

Aqueous humor

A

Constant flow of solution clears the drug

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10
Q

Vitreous humor

A

Hydrogel
Not a lot of flow, only diffusion
Excellent culture for bacteria
Poor penetration of antibiotics

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11
Q

Conjunctiva

A

Drug loss via pre-corneal clearance due to large blood supply

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12
Q

Choroid

A

Highly vascularized
Allows for systemic clearance through blood

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13
Q

Physiological factors of drug uptake

A

Tear film and nasolacrimal drainage
Blinking
Protein binding
Metabolism and efflux
Conjunctival loss

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14
Q

Formulation factors for drugs in the eye

A

Instilled volume
Drugs and adjuvants
Surface tension
Osmolality
PH
Viscosity

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15
Q

Instilled volume

A

Smaller volume—>slower drainage—> increased residence time
Ideally high concentration of drug in small volume

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16
Q

Drugs and adjuvants

A

Drugs can often cause corneal irritation leading to increased tear secretion
Some drugs can also decrease tear secretion

17
Q

Surface tension

A

Lower surface tension—> tear film destabilization —> reflex blinking
Lower surface tension disrupts tight junctions in the mucus layer —> increased corneal permeability

18
Q

Osmolality

A

Hypotonic—> swelling and increased permeability
Hypertonic—> loss of drug and loss of surface cells
Tears regain Osmolality in 1-2 minutes

19
Q

PH

A

Optimal 7-7.7
Acidic: reflex tears and blinking
Basic: saponification and loss of membrane integrity

20
Q

Viscosity

A

High viscosity: prolongs retention time, too much can lead to reflex tears

21
Q

To increase viscosity

A

PVA or methyl cellulose

22
Q

Ophthalmic formulations

A

Vehicles—increase viscosity and contact time
Preservatives—antimicrobial
Antioxidants—prevent product deterioration
Permeability enhancers—increased corneal penetration
Buffers—maintain pH
Tonicity adjusters—ensure isotonicity

23
Q

Benzalkonium chloride

A

Preservative for multi-use containers
Destabilizes corneal cell membranes
Increases corneal permeability

24
Q

Side effects of preservatives

A

Stinging/burning
Dry eye sensation
Tearing
Anterior blepharitis
Conjunctival follicles
Superficial punctuate keratitis

25
Q

Solution advantages

A

Easy to prepare
Inexpensive
Easy to use

26
Q

Solution disadvantages

A

Cannot sustain high drug concentrations

27
Q

Delivery issues with topical ocular delivery

A

Limited area of drug absorption
Selective corneal epithelial barrier
Tear clearance and nasolacrimal drainage
Vascular clearance

28
Q

Patient issues with topical ocular delivery

A

Frequent administration
Difficulties with application
May temporarily affect vision

29
Q

Strategies to improve bioavailability

A

Increase tear film contact time
Increase corneal permeability

30
Q

Increase tear film contact time

A

Mucoadhesive polymers

31
Q

Increased corneal permeability

A

Prodrugs
Penetration enhancers
Drug cyclodextrin complexes
Lipid-based carriers
Iontophoresis

Drug Delivery 2 (8 decks)

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