Ophthalmic Drugs Flashcards
(62 cards)
What are routes of administration of ophthalmic drugs?
Topical
Systemic - must overcome blood-ocular barrier
Why are topical preparations usually preferred for ophthalmic medications
High local concentration with low systemic absorption
Reach anterior chamber of the eye
Systemic drugs may not reach part of the eye in sufficient concentrations
The dog/cat eye can hold ________________ amount of fluid and excess will drain into the __________________
One drop; nasolacrimal duct
How long should you wait between administration of ocular drops? Why?
5mins
Wait for first medication to be absorbed
Adding one drop after another will wash out the first/overflow into the nasolacrimal duct
What are adverse effects of using topical ophthalmic medications
Irritating to eye
Effects of drug if it is systemically absorbed or swallowed (usually little concern)
Alteration of function or diagnostic tests
Difficult to administer repeatedly and frequently
Short acting at site -> washing by tears
What is used commonly in equines to administer ophthalmic drugs frequently?
Subpalpebral lavage system
The __________________ nervous system will cause miosis and contraction of the ciliary body
Parasympathetic
Constriction of the iris sphincter
Contraction of the ciliary body will cause lens accommodation for __________ vision
Near
What effect will the PSNS have on aqueous outflow ?
Lifts the iris away from the trabecular meshwork and increases the uveoscleral angle => increased outflow
The ______________ nervous system will cause relaxation of the ciliary body and mydriasis
Sympathetic
The sympathetic nervous system will cause lens accommodation for ______ vision
Far
What effect with the SNS have on aqueous humor?
Ciliary body relaxation causes decreased angle of the uveoscleral angle -> accumulation of aqueous humor
This is why SNS drugs are contraindicated in glaucoma (increase IOP)
What effects will mitotic drugs have?
Pupil contraction
Open drainage angle => improved aqueous outflow
When should mitotic not be used?
Direct and indirect acting parasympathomimetics
What is the MOA of pilocarpine
Direct acting parasympathomimetic
What is the duration of pilocarpine?
Miosis lasting 2-6 hours
What is the main clinical use of pilocarpine
Diagnosis of parasympathetic lesions
Uncommonly used to treat glaucoma and keratoconjunctivitis sicca ‘dry eye’ (KCS)
What is the MOA of atropine?
Direct acting parasympathoLYTIC
What effect will atropine have on the eye and what is its main indication?
Mydriasis
Cycloplegia (paralysis of ciliary muscle)
Reduced pain associated with corneal or iris disease
Break up synechiae in uveitis (ciliary body attached to lens-> ciliary body relax/dilate pupil to detach from the lens)
When is topical ophthalmic atropine contraindicated
Primary glaucoma!
What are precautions to using atropine topically in the eye?
Cycloplegia -> horse may panic
Very bitter taste -> cat will froth at the mouth
Generally minimal systemic absorption but in some cases may see increased heart rate
What is the MOA of tropicamide?
Direct acting parasympathoLYTIC
Causing mydriasis and cycloplegia
How does the duration of tropicamide compare to atropine?
Tropicamide (onset 15mins; duration 6hrs) has faster onset and shorter action than atropine (onset 1hr; duration 120+ hrs)
What are the indications for tropicamide?
Dilate pupil for ophthalmic exam
Prevent adhesions after cataract surgery
