Pharmacology - Lecture 1 (Ocular Pharmacology) Flashcards
What are drugs used in the eyes for
Examples include:
- glaucoma
- eye exma
- pre surgical
- keratocnjuncitvitis sicca (KCS)
- inflammation
- infections
For eye physiology, discuss 1) ciliar muscle
2) constrcitor pupillae (includes 2 different muscles)
Ciliary muscle: Accomodation - far vision; relaxation of the ciliary muscle leads to more tension on lens; lens the narrows to increase focal popiint for far vision
conrtictor pupillae inlcudes sphincter muscle and radial muscle
- for the sphincter muscle, contraction reduce pupil size (miosis)
- for the radial muscle,, contraction increases pupil size (mydriasis)
Which ton eodminates for the cilliary muscle
Cilioary muscle:
- parasympathetic tone dominates
- M3 receptor increases Caclium which mediates contraction –> so the muscle relaxes when parasympathetic tone is removed
- weak Beta adrenergic effect to relax muscle
which tone
WHich receptors mediate the sphincter muscle and radial muscle
SPhincter muscloe: mediatred via an M3 muscarinic receptor
Radial muscle: mediated by an apha 1 adrenergic recpetor
Discuss the lacrimal gland and its function and the recpetor associated with it
- Lacrimal gland: tear formation increased by M3 muscarinic recpetor
Discuss how fluid is formed and which recpetor causes decreased fluid fomration
Fluid fomred by ciliary epithelium
- Fluid formation increases with presence of B2 activation (direct effect to increase cAMP
- Decreased fluid fomration with alpha 2 recpeotrs
Carbonic anyhydrase participates in fluid formation
Discuss the 2 routes in which fluid is drained
route 1) conventional drainage route some contraction of ciliary muscle can imrove drainage; it opens netwrok of connective tissue in trabeculae —> involves Muscarinic (M3)
Route 2) AAlternative drainage route –> this is also knonw as the uveoscleral route and it is stimulated by PGF2 alpha
- Alpha agonists cause weak mydriasis (Note that muscarinic blockers cause strong mydriasis)
Discuss M3 agonists
M3 agonists:
- accomodation (near visioin)
- miosis (pinpoint)
- tears
- increased drainage (conventional route)
Discuss M3 antagonists
- profound mydriasis (dilated)
- may rpecipitate acute pressure inbcrease
- dry eyes and loss of accomodation
NOTEthat profound mydriasis (dilation) results from the parasympathetic nervous system dominating
Discuss B-agonists
B agonists increase fluid formation
Discuss B antagonists
Decrease fluid formatiomn
ALpha agonists
Relatively weka mydriasis (alpha 1)
decreases fluid formation (direct via alpha 2 or indriect (vascular) via alpha 1)
Discuss PGF2-alpha agonists
increase drainage (uveoscleral route)
Discuss Glaucoma
- excessive increase in intracocular pressure (IOP)
- left untreated will cause blindness
- the increased introcular pressure is associated with the anterior chamber 9filled with AQ humor)
- Left untreated, will cause blindness
- defintive treatment i ssurgiocal
- acue crisis can be handled with drugs
- Long term drug treatment not normally possible
- Treatments are orineted towards either increasing fluid fomrationor decreasing fluid formation
combinations can produce additive effects
Duiscuss druygs used for glaucoma
Topical PGF2alpha analog: latanoprost (XANATAN)
- activates uveoscleral drainage oathway
- Used in dogs (BUT NOIT if uveitis is poresent) but NBOt cats
- Not a good choice if inflammation is present
- Generally well tolerated but can see: miosis, redness, discomfort, blurred vision, allergic reaction, macular edema, iris pigemntation and eye lash growth
- Rememeber, as a PGf2 analog, if latanoprost gets systemic it will have reproductive effects and could cause bronchocnstriction
Discuss the drugs used in glaucoma Part 2
Topical Beta blocker: timolol
- decrease dluid formation by blocking B2 receptors on the ciliary epithelium
- useful in cats and dogfs
Caution using timolol in pateints with resiratory or Cv disease (bronchospams)
Why timolol? 1) more potent than propanolol 2) no local anesthetic action
Discuss drugs used in glaucoma part 3
Carbonic anyhydrase inhibitors (so by inibiting these, fluid formation is inibitied
- aqueous fluid is made in the ciliary epitheloium
Active secretion: Carbonic anhydrase helps set up the gradients that results in aqueous fluid obeing secreted into theposterior chamber
Therefore, carbonic anhydrase inhhibitors will reduce abiloity to form fluid
disucss carbonic anyhydrase inibitors in dogs vs cats
Normally, carbonic anhydrase inhibitors are given topically
Effectvie in dogs and cats (normally used with timolol)
Remmeberm, cats are morre sensitive to side effetcs if given systemically (metabolicn acidosis)
CAs are effective in dogs and cats (normally used with timolol)
Discuss drugs used in glaucoma part 4
Topical parasympathomimetic:
1) indirect via AChE inhibitor (demcarium) which functions to: 1) will increase the concetrayion of ACh at PNS synapses 2) indirectly leads to muscarinic recepror activation
2) direct via muscarinic R agonist (pilocarpine):
copnstrictionof ciliary muscle improves drainage
constrictionof sphincter muyscle may also help
Topical parasympathomimetic will function to: will increase tear formation
potential systemnic side effects DUMBSLED: diahhrea, urination, miosis, bradycardia, salivation, lacrimation, emesis, dyspnea (difficulty breathing)
Discuss pe
Discuss topical sympathomimetics
Topical sympathomimetic:
- epinephrine causes a decrease in fluid formation .. thught to be due to alpha anrenergic actions
