Unit3_Pharma Flashcards
What is the difference between ophthalmic solution and ophthalmic suspensions?
Suspensions have limited solubility
Increased time in the cul-de-sac of the eye facilitates what in terms of drug administration?
Increased absorption
The rate and extent of drug absorption into ocular structures is determined by: ? (5 things)
- ) Time drugs remains in cul-de-sac and precornal tear film.
- ) Elimination by nasolacrimal drainage.
- ) Drug binding to tear proteins.
- ) Drug metabolism by tear and tissue enzymes.
- ) Diffusion across cornea and conjuctiva.
After you give the drops, the appearance of the drugs in the Aqueous Humor is dependent on what?
Passive diffusion through the cornea.
The cornea is trilamellar. What order are the layers types in?
Fat-Water-Fat
The cornea is a tri-lamellar structure (“Fat-Water-Fat”), drugs that have what properties are best suited for transcorneal absorption?
Drug with both HYDROphillic and LIPOphillic properties
the systemic absorption of topically administered ophthalmic meds primarily occurs vi ______?
Nasolacrimal drainage
What are the 3 possible absoroption pathways of topcially administred ophthalmic drugs?
- ) Nasolacrimal route
- ) Corneal route
- ) Conjuctival-scleral route
Localized biotransformation of ocular drugs can be significant due to the presence of a variety of enzyme systems including: ? (6)
- esterases
- oxidoreductases
- various transferases (conjugations)
- monoamine oxidase
- COMT
- 11-beta-hydroxysteroid dehydrogenase
Why are esterases one of the more important enzymes to consider in terms of drug breakdown?
Many active form of ophthalic drugs are ESTERS, b/c they have great lipid solubility –> better penetration of cornea.
What is the leading cause of blindness?
1st in Hispanic-Americans
2nd in African-Americans 3rd in Caucasians
Glaucoma
What are the risk factors ~ Glaucoma?
- IOP
- Hx
- being black
- myopia and HTN
What is the normal IOP?
10-15mmHg above ATM
What is increased IOP ~ glaucoma?
> 22mmHg above ATM
Aqueous humor is secreted slowly and continuously by the cells of the epithelium covering the ciliary body –> drains into (what structure)?
canal of Schlemm.
(runs around the eye close to the outer margin of the iris)
Can you surgically Tx Open-Angle Glaucoma?
yes, but may not be possible.
Life-ling Tx with drugs better.
What is the overall strategies for treatment of Open-Angle Glaucoma? (3)
Initial: Prostatglaning analog (PA)
Then: Good response to PA, but need more; + Beta-blocker -or- CA-inhibitor, -or- Alpha-2-Agonist.
if poor response to PA, sub in a different class of drug
Combining drops from different classes can cause a __________ reduction in the intraocular pressure than monotherapy
greater reduction
List the drugs used to treat open angle glaucoma that increase outflow of aqueous humor. (3)
Prostaglandin analogs: Latanoprost (Xalatan), topical PGF2-alpha prodrug.
Alpha-Agonist (Alpha-2 is preferred)
Cholinergic Agonist (aka miotics) [less commonly used today]
List the drugs used to treat open angle glaucoma that reduce production of aqueous humor. (2)
Beta-Atagonists. Beta-2 is best
Carbonic Anhydrase inhbitors (Dorzolamide) [2nd/3rd line Tx]
What is the MOA of Ophthalmic Beta-blockers (Timolol)?
Decrease Aq. Humor secretion from the ciliary epithelium.
What is the MOA of Ophthalmic Prostaglandins (Latanoprost)?
Increase Aq. humor outflow
What is the MOA of Ophthalmic Cholinomimetics (Pilocarpines)?
- Increase ciliary muscle contraction
- opening of trabecular meshwork
- increase outflow
What is the MOA of Ophthalmic Alpha-Agonist (non-selective: Epi, dipivefrin)?
increase outflow; probably via the Uveoscleral veins.
What is the MOA of Ophthalmic Alpha-2-Selective drugs (Apraclonidine, brimonidine)?
decrease Aq. humor secretion
What is the MOA of Ophthalmic Diuretics (Acetazolamide, dorzolamide)?
Decrease secretion due to lack of Bi-carb.