Pharm 2 - Ocular 1

duhasopu's version from 2017-10-10 21:41


Question Answer
How would you describe systemic access to the eye? why is it the way it is?it is quite secluded! there are blood-retinal barriers, blood aqueous barriers, and blood vitreous barriers
which part of the eye is most difficult to get to?posterior segment of eye (The posterior segment is the back two-thirds of the eye that includes the anterior hyaloid membrane and all of the optical structures behind it: the vitreous humor, retina, choroid, and optic nerve)
what is the usual way to administer drugs to the eye, and why? Precautions about this?The eye is relatively secluded from systemic access, so most drugs are applied topically! Be careful of irritation/toxicity
what are the main targets of the eye he mentions?conjunctiva and cornea, eyelids, iris, ciliairy body, vitreous, retina, choroid, posterior orbit, nasolacrimal system
when would you use a topical route of admin (for what parts of the eye)?conjunctiva, cornea, anterior uvea, eye lids
when would you use a systemic route of admin (for what parts of the eye)?eye lids, posterior segment, optic nerve, (anterior segment)
when would you use a subconjunctival route of admin (for what parts of the eye)?cornea and anterior uvea (vascular portion of the eye-- the ciliary bodies, the choroid, and the iris)
when would you use a intraocular (intracameral) route of admin (for what parts of the eye)?anterior chamber or posterior segment
what does intracameral mean?within a chamber, such as the anterior or posterior chamber of the eye (camels in chambers)
when would you use a retrobulbar route of admin (for what parts of the eye)?posterior segment, optic nerve
when would you use a intravitreal injection/device route of admin (for what parts of the eye)?incommon in vetmed
what are the anatomical entities that serve as a drug reservoir?(ie, where do drugs get 'stuck' in the eye?) cornea, lens, uveal pigment(melanin)
what are 4 characteristics of the eye which make drug delivery difficult? (physical barriers)(1) continuous tear flow (washes stuff away) (2) epithelial tissue with poor permeability (lots of layers of epithelial cells) (3) limited circulation to the eye (4) the blood-aqueous barrier
what is a biochemical characteristic of the eye, which when combined with the physical barriers, makes drug delivery to the eye difficult?outward transport proteins (ABC transporters)
fluid in the ant chamber is? post chamber is?ant= aqueous humor. post= vitreous humor
what is the particular substance in the eye that some drugs will bind to?melanin
what is metabolism of drugs in the eye like?there is enzymatic biotransformation in the eye, esp with esterases (use of prodrugs for epinephrine and prostaglandine F2-alpha)
what kinda Vd do eye drugs need?large


Question Answer
What is the main route of entry when drugs are topically administered?through the cornea
What is the estimated elimination half-life of drugs in tears?3-6 min
How can you change the elimination half-life of drugs in tears? (2 ways) (and what is the t1/2?)(3-6 min). (1) changes in tear production (2) changes in drainage and blinking rate
What happens to the topically administered drug that "spills over"?it is is absorbed by mucous membranes (like nose or conjunctiva)
Once the topically administered drug enters the eye (how?), how is it distributed? where is it absorbed from there?(enters via cornea) distributed by aqueous humor circulation. It then diffuses into the iris, ciliary body, and lens
What is the VD of a topically administered drug like?needs to be HIGH to get through cornea and such
If drugs cross the conjunctiva and the sclera, how are they eliminated?eliminated mainly by choroidal circulation (pic on slide 9). (BVs between retina and sclera)
How much drug usually reaches the vitreous and retina? HOW does it reach these structures?only small concentrations make it there, by diffusing along the scleral spaces
Explain the three paths a drug can take to get from topical admin (tears) to SYSTEMIC circulation?(1) Tears--> CORNEA(main route)-->aqueous humor-->iris(lots of BVs)-->systemic
(2) Tears-->conjunctiva-->sclera-->ciliary body(lots of BVs)-->systemic
(3) nasolacrimal route (mucous membs with lots of BVs)--> systemic. (note: cornea and sclera can have the drug go back and form from sideways, same thing with iris and ciliary bodies)
What are the two diff types of liquid topical drugs? explain what they are(1) solutions (drugs dissolved in a solute) (2) suspensions (drugs as solid particles suspended in a solute-- NEED TO SHAKE THESE)
4 advantages to solutions/suspensions?(1) Less effects on vision (most are see through, and can be blinked away if can't see)
(2) Less incidence of contact dermatitis (isnt staying in one place for super long- I think the 3-6min tear t1/2 plays into this)
(3) Less toxic to ocular structures
(4) Easier to apply
What are the 4 disadvantages to solutions/suspensions?(1) SHORT contact time (2) dilution effects (3) expense (4) inc systemic absorption
How much is a sufficient dose with solutions/suspensions, and how do you apply?allow drop to fall on eye one drop is enough
What is an ointment?drugs suspended in oil
What are the 4 advantages of ointment?(1) Longer contact time
(2) Not diluted
(3) Protects cornea from drying
(4) Less expensive
What are the 5 disadvantages of ointment?(1) difficult to dose precisely (2) inc ocular discharge (3) more difficult to admin (4) more contact dermatitis (5) may delay epithelial wound healing
How much is a sifficient dose with ointments?5mm ribbon is adequate
Which type of topical drug is less expensive? which one delays epithelial wound healing? which one has more systemic absorption?ointment less expensive, ointment delays healing, solutions/suspensions have more systemic absorption
Subpalpebral lavage system is used for what, with which type of topical drug? how does it affect drug concentrations? what are the disadvantages?used as a constant perfusion system for SOLUTIONS. Increased drug concentrations (20% vs 3-4%) (note: i am not sure if the process is concentrating it, or if it means you can USE stronger concentrations). adverse effects are abscesses, and blepharitis
5 things which determine absorption after topical admin?(1) Time the drug stays in the cul-de-sac and precorneal tear film
(2) Elim by nasolacrimal drainage
(3) Drug binding to tear proteins
(4) Drug metabolism by tear and tissue enzymes
(5) Diffusion across cornea and conjunctiva
What is/are ways a topically administered drug can get into systemic circulation? (not path, just the structure)nasal mucosal absorption (mentioned twice), iris, ciliary body
Local ocular distribution happens via what structures?conjunctiva and cornea
Transcorneal distribution leads to the drug going where?cornea--> aqueous humor--> intraocular structures AND systemic circulation

Subconjunctival Therapy/ Intracameral Therapy

Question Answer
How does subconjunctival therapy work? what must you do?medication is injected under the conjunctiva. Requires SEDATION and TOPICAL ANESTHETIC
What is the max volume to be injected in subconjunctival therapy? (sp diffs)dog 0.5ml. horse 1ml
How does a subconjunctivally administered drug distribute? (2)(1) Soak through sclera (-->iris-->ciliary body)
(2) Escapes out the needle hole and is absorbed though the cornea
What kinda drugs is subconjunctival therapy used for?abx and corticosteroids
What are the two big advantages to subconjunctival therapy?(1) Long duration of effect: depot storage
(2) High conc in anterior chamber
What are the three main disadvantages of subconjuntival therapy?(1) Limited # of injections
(2) Scar tissue formation
(3) Can't be removed once given
What is the benefit of intracameral therapy?you can achieve very high drug conc
What are the 3 big risks of intracameral therapy?hemorrhage
retinal detachment/degradation
How do you do intracameral therapy?inject drug into aqueous or vitreous fluid
What two things are required for you to perform intracameral therapy?General and topical anesthesia
Sterile techniques

Agents Acting on the Pupil

Question Answer
What is the word for dilation of pupil?Mydriasis
What is the word for contraction of pupil?Miosis
What affect do opioids have on the pupil?Pinpoint pupils
What is the pupillary response to sympathomimetic/parasympathetolytic drugs?Dilation/Mydriasis
What is the pupillary response to parasympathomimetic/sympatholytic drugs?Contraction/Miosis


Question Answer
If you're thinking of using antibiotics, what should you know?Do a tentative dx of pathogens-- dont treat non-infected eyes!
*How do you tentatively diagnose a bacterial eye infection?Corneal ulcer scrapings--> gram staining
*You should always do a sensitivity test when about to tx eye with abx. what do you need to keep in mind with sens. tests? Drugs stay local on the eye so you might have to adjust interpretations of sensitivity tests, b/c the drug maintains a high local concentration
*Which animals are usually infected by G+? G-?G+(staph/strep) usually dogs/cats/horses. G- usually rumis (ruminants are rated more negatively than the other animals)
How long to abx stay on the cornea?Short time on cornea: 3-4% after 5 minutes
*1st choice antimicrobials for corneal ulcers and bacterial conjunctivitis (non-specific infections)? (2)(1) NPB-- this is bacitracin+neomycin+polymyxin B.(aka neopolybac) (neo and poly do G- and baci(penicilin equivalent) does both bc cell wall distruction) (2) NPG-- this is neomycin+polymyxin B+gramicidin (In short--- combine G- and G+ shit to cover your ass)
*What is the first choice abx for SMALL ANIMALS? note about this? side effects?Chloramphenicol. NOTE: DOES NOT WORK ON PSEUDOMONAS. look out for HYPERSENSITIVITIES (first choice-- throw chloriene in their eyes! Excellent!)
*Which abx will penetrate intact cornea?Ciprofloxacin (Cipro, Cornea) (I will sip fluids through your cornea) (and so does chloramphenicol, bc that's first choice for small animals, and so it does both)
NEOMYCIN/POLYMYXIN/BACITRACIN (NEOPOLYBAC) (NPB) is used to tx what? what is its spectrum?Corneal ulcers, conjunctivitis, Broad Spectrum
TICARCILLIN/CLACULANATE/AMPICILLIN has what side effects?Hypersensitivities
Is chloramphenicol static or cidal?Static (even though it's number one in small animals, that doesnt mean it's awesome at everything, like killing)
Are fluoroquinolones (ciprofloxacin) static or cidal?Cidal (flo will kill a bitch)
What does tobramycin tx best in the eye?Pseudomonas (toby will kill pseudo-posers)


Question Answer
antifungals used for what dz?keratomycosis
how should you tx keratomycosis?AGRESSIVE tx, surgical intervention usually required so drug can penetrate
what three classes of antifungals do you usually use on the eye?polyene antibiotics, imidazoles (remember: IM ME,KC!), nucleoside analogs
polyenes--> amphotericin B--> penetration is like? use against what? spectrum?poor penetration, broad spectrum, more active against yeast (yeast on all my membranes, yo)
polyenes--> natamycin--> how is it administered? what does it work well against?topical suspension, more effective against fungi, less against yeast, good against Fusarium(type of fungi) (FUNA)
how do you admin azoles for eye (miconazole, clotrimazole, itraconazole)use derm creams on eye (well tolerated)
what is the penetration of polyenes like? how much binding do polyenes have?highly tissue bound with poor penetration (they stick into the membrane and cause pores, which means they wont go inside, remember?)
what are the two polyenes used?amphotericin B and natamycin (many AMs for NAT)
what should I know about amphotericin B (spectrum? how safe? to tx what?) what group does it belong to?polyene, BROAD spectrum, toxicity(renal tox, hypokalemia). tx yeast!
Nucleoside analogues--> which drug? (spectrum? what two other things should we know about the drug?)FLUCYSTOSINE. broad spectrum, Synergistic w/ Amphotericin B, and resistance can develop (too much AMP will give you the FLU)
flucytosine can be synergistic with what? what group does it belong to? what should we know about it?synergistic with amphotericin B. Resistance happens quickly. Belongs with nucleoside analogues
what are the three azoles used on the eye?MICONAZOLE, CLOTRIMAZOLE, ITRACONAZOLE (MY IT CLOTTED in my eye)
miconazole--> spectrum? how is it administered? how bioactive is it? does it bind to things? what is it used to tx?BROAD spectrum, administered via subconjunctival injection, 30% bioactive, highly tissue bound, and used to tx yeast and fungi (Mi overachiever antifungal doesnt wanna sit on the eye, it wants to GET IN THERE)
how is clotrimizole administered? what is it used to tx?derm cream used on eye, tx aspergillus
itraconazole---> spectrum? what is the commercial form? what is it used to tx?broad spectrum, no commercial form (combine with 1% DMSO), used to tx fungi (itra was a fun gi, he took a lot of DMSO though)
combined with 1% DMSOitraconazole ( It raDM SO hard)
what tx aspergillus?clotrimizole (vag stuff to treat asparaguses on your eye. Yay.)
which azole tx yeast?miconazole ( MI YEAST infxn)
what is the optimum tx for corneal ulcers?equal amounts of: natamycin - tobramycin - cefazolin (combination is more effective than individual tx) (one antifungal and two abx, tobra for pseudomonas) (got an ulcer? I bet you're NotTooCarefree)


Question Answer
what are the main reasons youd use use antivirals for the eye? who does this usually pertain to?herpes virus keratitis and keratoconjunctivitis. RARE in dogs. MORE COMMON but self-limiting in cats and horses
putative viral superficial keratitis (who? why?)HORSES, unknown cause and no associated systemic dz
DEOXYURIDINE (what should you know about this antiviral?)idoxuridine is the modified form of deoxyuridine, know that they are eptheliotoxic - teratogenic (skin cancer as agressive as de ox)
aciclovir (what should we know about this antiviral?)less toxic
IFN γ (interferon gamma)- what does this drug do? who do you use it in?cats, horses(?), it inhibits viral protein synth

admins (again, together)

Question Answer
topical--> aborption speed? benefit?prompt absorption. Safe and easy
Subjunctival--> speed? use?Prompt & Sustained. Use for Ant. Seg infections, posterior uveitis
Intraocular---> speed? uses?speed is Prompt. US in Ant. Seg surgery, infections
Intravitreal--> speed? uses? speed is Immediate & use in Sustained Endopthalmitis, renitis