Ocular Pharmacology Flashcards
Name the four ACh agonists used in the eye.
ACh (miochol), carbachol, methacholine, pilocarpine
What are the effects of ACh agonists and what are they therefore used for?
pupillary constriction, increased aqueous outflow; used in cataract surgery and glaucoma treatment
Name the five ACh antagonists used in the eye.
atropine, scopolamine, homatropine, cyclopentolate, tropicamide
What are the effects and uses of ACh antagonists?
pupillary dilation and paralysis of ciliary body; used to dilate the eyes for exams and improve comfort during active inflammation (uveitis)
Which ACh antagonist has the shortest half-life and time to maximal action and is therefore used for eye exams?
tropicamide
What are the three things necessary for accommodation?
- Thickening of the lens 2. Convergence of the eyes 3. Pupillary constriction
In the eye where are the nicotonic and muscarinic receptors found? How are each of these blocked (by what drugs)?
Nicotonic- found in the extraocular muscles; blocked by d-tubocurarine Muscarinic- found in the ciliary body and iris; blocked by atropine
What is the only application for nicotinic agonists in ophthalmology? What specific drug is used?
The only application is to use edrophonium (an indirect nicotinic agonist) to diagnose myasthenia gravis.
What happens in the eye when the sympathetic system is activated?
Pupil dilation, Lifting of eyelid, facilitation of aqueous production, dilation of blood vessels and increased outflow of aqueous humor
What is the primary NT for the sympathetic system in the eye?
Norepinephrine
What is the main parasympathetic NT used in the eye?
Acetylcholine
Name the direct sympathetic agonists and their effects.
- Phenylephrine- mimics NE alpha 1–> dilation of pupil
- L-epinephrine- alpha and beta effects
- Dipivalyl epinephrine- prodrug of epinephrine
- Bromondine tartrate- selective alpha 2 agonist which suppresses aqueous humor production
- Apraclonidine- alpha agonist (amino derivative of clonidine which does not cross the BBB and has minial effect on systemic BP)
- Clonidine- alpha adrenergic agonist (lowers IOP through CNS effects)
What makes Apraclonidine unique?
It is a direct sympathetic alpha agonist that is an amino derivative of clonidine which does not cross the BBB and has minial effect on systemic BP
Name the indirect sympathetic agonists and their effects
- Cocaine- prevents reuptake of NE 2. Hydroxyamphetamine- release NE
Name the antagonists of the sympathetic NS and their effects
- Dapiprazole- reverses action of tropicamid and phenlyephrine; blocks alpha adrenergic receptors in the smooth dilator muscle of iris
- Timolol- non-specific beta 1 and 2
- Betaxolol- beta 1 blocker
- Carteolol- non-specific beta 1 and beta 2 blocker
- Levobunolol- beta 2 blocker
- Metipranolol- non selective beta 1 and 2 blocker without significant intrinsic sympathomimetic activity, only a weak membrane stabilizing activity and a weak myocardial depressant.
How do some sympathetic agonists aid in the treatment of glaucoma?
Epi compounds are thought to increase aqueous outflow by dilating episcleral vessels.
How do sympathetic antagonists (ie/ beta blockers) aid in the treatment of glaucoma?
Beta blockers such as timolol, betaxolol, and levabunalol reduce IOP by reducing aqueous production at the ciliary process.
What is the only specific beta blocker used in ocular pharmacology?
Betaxolol (beta 1 blocker)
How do some parasympathomimetics lower IOP in the treatment of glaucoma?
By spreading the trabecular meshwork through contraction of the ciliary muscles. Direct agonists used- pilocarpine and carbachol Indirect agonist- echothiphate (not used so much anymore b/c of side effects)
What are some alternative glaucoma medications?
Prostaglandin analogs (Latanoprost, Bimatroprost, Travoprost, Unoprostone isopryl) – increase uveoscleral outflow Carbonic anhydrase inhibitors (Dorzolamide hydrochloride, Brinzolamide, Diamox) – reduce aqueous production Combination medications Combigan (Alphagan and Timolol) Cosopt (Trusopt and Timolol)
What are some first line medications used for treatment of glaucoma?
What are the three main signs of Horner’s syndrome?
Miosis, Ptossis and Anhydrosis
How can you confirm Horner’s syndrome?
One way is with pharmacological testing. Cocaine inhibits reuptake of NE–> the flood of NE will cause pupillary dilatation if the sympathetic system is intact.
In Horner’s pupillary dilatation will NOT occur.
How do you separate a preganglionic vs. a postganglionic lesion in Horner’s?
Paredine 1% (hydroxyamphetamine) applied topically to the eye actively releases NE. If paredine is given and pupillary dilatation occurs then the lesion is at the level of the 1st or 2nd order neuron (the 3rd order neuron is intact but not receiving a stimulus).
If the pupil does NOT dilate, then the 3rd order neuron is dysfunctional (which indicates a more benign process).
