Ocular Pharmacology Flashcards
lots of challenges to treat the eye
Lack of penetration
Topical drugs require frequent admin
Long duration of therapy
Drug absorption
Major barriers that change w topical or systemic administration
drug absorption - topical
No problem for superficial infection - deeper is concerning physiological barriers
- tear turn over
- drainage out nasolacrimal ducts
- blinking
All decrease contact time of drug and eye
Anatomic barriers for deeper eye absorption
Multiple layers - lipophilic layers for epithelium and endothelium but hydrophilic in stroma
Topical drug absorption
Lipophilic, unionized, low MW administered frequently @ high doses will reach greater ocular concentrations
Systemic absorption
Blood-aqueous and retinal barriers
- non fenestrated capillaries
- tight junctions
- p-glycoprotein efflux pumps
Systemic drug absorption
Lipophilic, unionized, low MW drugs w minimal protein binding that reach high systemic concentrations will reach greater ocular concentrations
Inflammation and absorption
Inflammation increases drug absorption due to broken down blood ocular barrier
Ideally choose a drug that will have good penetration without factoring in inflammation
Ocular PK
Drug distribution through vitreous humor takes a long time
Drug probably wont be metabolized in the eye
Drainage /elimination through the chamber angle and is often slow. High /frequent dosage+ slow drainage = better chances at reaching high concentrations
Routes of admin
Depends on location of disease
Systemic administration
Appropriate for posterior segment, endophthalmitis, orbital tissues
Also for anterior segment, corneal stroma - depends on degree of inflammation
Systemic is not ideal for corneal surface/conjunctiva
Antibacterial systemic admin
Lipophilic - minocycline, enrofloxaxin, chloramphenicol, macrolides, trimethoprima-sulfa combo
Hydrophilic - B lactams, aminoglycosides
Systemic admin for antifungals
Fluconazole, voriconazole
Itraconazole XX - too lipophilic and will get stuck in stroma
Antivirals - all hydrophilic should be treated topically
topical admin
Corneal surface/conjunctiva disease
Lipophilic drugs are better for penetrating intact cornea
Not preferred for posterior segment disease
Methods to increase topical drugs absorption/efficacy
Increased drug concentration in formula
Increase volume admin
Increase dose frequency***
Decrease corneal thickness
Use specialized formulations
Increase contact time
Stick needle into eye - XX
