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52 Cards in this Set

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How is the clinical pharmacology of the eyes unique?
1.primary route of drug delivery is topical
2.small quantities of drug can rapidly achieve high concentrations
3.effects on pupillary size and intraocular pressure are readily measured.
Only what form of the drug will cross the lipid membranes of the eye?
Uncharged form.
What substance is a negatively charged yellow dye?
Fluorescein
What is commonly used in offices and emergency rooms to detect corneal abrasions?
Fluorescein
Why is Fluorescein used for corneal abrasions?
The point here is that fluorescein is a negatively charged compound and will not traverse intact membranes. It is only taken up into deeper structures where the membrane has been disputed. Therefore, where-ever we see yellow, there is a lesion of the cornea.
Is there significant systemic absorption for most drugs applied to the surface of the eye?
Yes
When applied to the eye, can the drug cause toxicity in other tissues?
NO--in most cases, the drug concentrations achieved in other tissues are too low to cause toxicity.
Most of the drug absorbed systemically occurs through what?
Lacrimal system.
What are the 3 routes drugs can use to be absorbed systemically from the eye?
1.Lacrimal system.
2.cornea-->aqueous humor-->iris-->systemic circulation
3.conjunctiva-->sclera-->ciliary body-->systemic circulation
What are the symptoms of Horner's Syndrome?
Ptosis and Miosis.
Horner's Syndrome is seen in patients with what type of illnesses?
Superior cervical ganglion.
RECEPTOR
ACTION
DRUG ADMINISTRATION
DURATION
TOXICITY
OTHER
DRUGS USED FOR OPTHALMOSCOPY
MYDRIATICS
Phenylephrine HCl
Alpha 1 agonist
Constrict radial muscle of pupil and cause papillary dilation/mydriasis, but does NOT cause cycloplegia
Liquid, nasal spray
Onset is within 30 minutes and has a relatively short duration of only 2-3 hours.
Sympathomimetic-->Alpha 1 activation causes vasoconstriction-->may result in elevation of BP, if significant one might see a reflex bradycardia.
CYCLOPLEGICS (BASICALLY ATROPINE TYPE DRUGS)
Tropicamide
Cyclopentolate
Muscarinic Cholingergic antagonist
Similar in action to atropine-->mydriasis and cycloplegia
Much shorter in duration than atropine, effects of atopine can last for days
Lasts 5-6 hrs. This has the advantage of a shorter duration.
Lasts 24 hrs.
Tachycardia, dry mouth, delirium (CNS effect), tachycardia, psychosis
GLAUCOMA
Beta-Adrenergic Antagonists (Nonselective)
Beta-Adrenergic Antagonist (Selective)
Timolol
Cartelol
Levobunolol
Metipranolol
Betoxolol
Excellent efficacy: Thought to decrease production of aqueous humor by 1/3. Formation of aqueous humor by ciliary body mediated by tonic sympathetic stimulation is blocked by timolol.
Topical administration is concentrated form-->brief contact time with surface of eye
Topical
Excess drug drains through the nasolacrimal duct into nose where it may get to systemic circulation. Timolol-->absorbed systemically-->drug reaches opposite eye-->can decrease intraocular pressure in the opposite eye.
Fewer side effects: Bronchospasm and respiratory failure (if someone has acute asthmatic attack or chronic asthma has greater potential to cause problems), Hypotension (dehydrated person is more likely), worsening CHF, Drugs inhibited CYP2D6 (quinidine, verapamil) may cause increase systemic toxicity of timolol. (Timolol is metabolized by this.)
PROTAGLANDIN ANALOG
Latanoprost
Prodrug, has to be metabolized to active compound
Low concentrations of PGF2a reduces IOP and do NOT cause inflammation. Increase uveosclearal outflow through iris root and ciliary body, perhaps by relaxing ciliary musculature.
Systemic side effects are uncommon. Occasional muscle and joint pain. Color of iris may darken in up to 10% of patients-->Usually in green-brown or blue-brown irises.
Epinephrine
Alpha stimulation causes early decrease in production of aqueous humor by constricting vessels supplying ciliary body and therefore decreasing ultrafiltration. Later, aqueous humor outflow may increase, mediated by alpha 2 and beta 2 stimulation.
-Cause slight amount of pupillary dilation, typically not though, does NOT cause cycloplegia
-Not as widely used for glaucoma as it used to be-->limited use due to its side effects
Dipivefrin
Nonselective adrenergic agonist
Prodrug
Apraclonidine
Brimonidine
Selective-Alpha 2 adrenergic agonist
Decrease production of aqueous humor
Apraclonidine does NOT cross BBB, and thus does not cause systemic hypotension. Side effects are dry nose and mouth and follicular conjunctivitis.
Preferred-less tachypylaxis. Brimonidine is more selective than apraclonidine but does not cause systemic side effects.
CARBONIC ANHYDRASE INHIBITORS
Dorazolamide
Brinzolamide
Acetazolamide
Decrease bicarbonate production, decrease Sodium and Water into the posterior chamber
Topical application can decrease IOP by up to 26%
For open angle glaucoma
Topical
Oral
B/c topical administration, much less systemic side effects than oral-->contraindicated if sulfonamide hypersensitivity or allergy
B/c topical administration, much less systemic side effects than oral
CHOLINERGIC AGONISTS
Pilocarpine
Carbachol
Echothiopate
OPIODS
Morphine
Cholinesterase Inhibitors
Direct Acting, parasympathomimetics cause constriction
Has to be given multiple times a day.
Side effects limiting (significant draw backs): fixed, small pupils, myopia, spasm of eyelids and brows.
E-W Nucleus in Occulomotor Nucleus-->Morphine works at the level of the E-W Nucleus to cause pinpoint pupils.
Effect is same regardless of route of administration.
HORNER'S SYNDROME
Cocaine
Amphetamines
Amphetamines act by increasing the release of NE from presynaptic nerve endings. If the lesion is preganglionic, then they have intact presynatpic nerve terminals and the hydroxyamphetamine can be expected to cause dilation of the pupil on the effected side. Functionally NE can still be released-->This is preganglionic Horners. BUT, if the lesion is postganglionic and the presynaptic terminals have been destroyed, application of hydroxyamphetamine will fail to produce a dilated pupil. This is postganglionic Horner's.
Apply hydroxyamphetamine to the surface of the eye.
Used to differentiate between a pre or post ganglionic lesion