Opthalmic – Chemistry – Flashcards
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Unlock answers| 4 uses of topical opthalmics |
glaucoma
infections
inflammation
dry eyes |
| injections are________ |
faster more deeply distributed (subconjunctival & intraocular) |
| 3 concentric eyeball layers |
outermost [conjunctiva,sclera] middle [uveal tract] innermost [retina] |
| inside eyeball divided by lens into |
| aqueaous (anterior) and vitreous(posterior) humor/segments |
| ____________divided by iris into anterior and posterior chambers |
| Aqueous humor |
| this part of the eye is responsibel for tear production |
| LACRIMAL GLAND |
| tears move from nasal cavity toward |
| NASOPHARYNX |
| OPTHALMIC DRUG TARGETS |
preocular structures
cornea
tissues in anterior and posterior seg
|
| Posterior segment is hot target for |
| topicals |
major pathways for topical opthalmics thru _____ and _____ |
| CORNEA(mostly) and SCLERA |
| 3 layers of tear film (*MLT like "melt" MNEUMONIC) |
Mucoid layer [adhesion of aqueous tear fluiid]
Lipid Film [was/cholesterol adhere to tear fluid]
Tear Fluid [elec,proteins,glucose] |
| This tear layer reduces evaporation of tear fluid |
| Lipid film |
| Keeps cornea wettable |
| Mucoid layer |
| CORNEAL MEMBRANES |
-epithelium -bowmans membrane -stroma - descemets membrane - endothelium |
| most important 3 layers for drug absorb in cornea (ESE) |
-Epithilium -Stroma -Endothelium |
CONTINUOUS W/ CONJUNCTIVA STRATIFIED EPITHELIUM [5-6 LAYERS AT CENTER,8-10 IN PERIPHERY]
**MAIN BARRIER FOR DRUG PASSAGE THROUGH CORNEA
|
| CORNEAL EPITHELIUM |
| IN THE CORNEAL EPITHELIUM SQUAMOUS CELLS ARE SURROUNDED BY___________THAT HAVE MICROVILLI(TO INC SA) |
| TIGHT JUNCTIONS |
| cORNEAL EPITHELIUM IS A _______BARRIER |
LIPOPHILIC [LIP RX PENETRATES BETTER RX IONIZATION STATE CAN BE IMPORTANT]
UNIONIZED DRUGS PASS THROUGH BETTER |
| THIS CORNEAL LAYER COMPOSED OF COLLAGEN FIBERS IS MOSTLY WATER AND IS 200 TIMES MORE PERMABLE THAN EPITHELIUM |
| STROMA |
SINGLE CELL LAYER OF CORNEA PROVIDING METABOLIC EXCHANGE BETWEEN CORNEA AND AQ. HUMOR MORE PERMEABLE THAN EPITHELIUM |
| ENDOTHELIUM |
| BEST ABSORBED DRUGS HAVE ___ OCTANOL/WATER PARTITION AT PHYSIO PH |
| "MODERATE" |
| Greater absorption occurs in ___ |
| Damaged epithelium |
Less than ______% of dose instilled as drops will cross cornea
Peak aq. conc between ________mins |
5%
20-60mins |
EYe drops are instilled in the _________
Drops range from___________ |
Lower cul de sac
25-56 uL [normal tear volume =7uL] |
Fates of applied eyedrop[BEFOREcross cornea] =
Spillage
Removal by nasolacrimal Drainage
Enzymatic Degradation |
Spillage [30uL can be accomodated w/out spillage in lower culdesac] [blinking inc spill.10 uL lost in one blink]
Removal by nasolacrimal Drainage [gravity&blink pumping mves rx through puncta to nasolacrimal apparatus]
Enzymatic Degradation |
| we blink our eye ________times per min |
15-20
(one blink causes 10 uL loss) |
Fates of applied eyedrop[AFTERcross cornea] =
Penetrate deeper intraocular tissue
Binding proteins
Elimination |
Penetrate deeper intraocular tissue [conc w/ in anterior chamber 2 orders mag less than applied prod] [amount getting to posterior signif less]
Binding proteins [lipophilic rx can bind to melanin in iris***darker iris slow/reduce rx]
Elimination [Sys circ-->thru canal of SCHLEMM] [thru uveal blood vessels] |
Opthalmic metabolism occurs after crossing the cornea and is a form of elimination. (prodrugs) EX:??[2] |
Dipivefrin to Epinephrine
Latanaprost to PGF2alpha |
| contribute to tissue absorption of topical opthalmics |
lacrimal sac nasopharynx cheecks and GI tract |
| Conjunctiva covers a greater surface areea than cornea and is more_______ |
| permeable |
Conjunctiva covers a greater surface areea than cornea and is more_______ |
permeable [highly vascularized] |
| No hepatic first pass in absorption of topical opth except in _____ absorption |
GI
[but over 50% of drug absorbed in eye is absorbed systemically anyway] |
| consider for topical opth. design |
| pH, osmolarity, viscosity,sterility |
Sterility
organism: w/ ex Rx
other bacteria:
|
Org:Pseudomonas Aeruginosa [Trypan Blue (recalled rx)]
staph aureis,candida albican,asperigillus niger,Escherichia coli |
| EXCIPIENTS: Antimicrobial preservatives are required in_____ |
multidose eye drops
[benzalkonium chloride BAC 0.01% or less]
[polyquad(polyquaternium-1 doesnt penetrate cornea well]
|
| benzalkonium chloride BAC effective agnst_____ |
| pseudomonas aeruginosa |
| Oxidants |
Sodium perborate
Purite (stabilized oxychloro complex) |
Tears pH
[irritation,sensitivity and reflex tears, & blinking seen in pH] |
7-7.4
[<6.6 & >9.0]--->>speeds drug elimination |
| buffers used to stabilize or solbilize = |
acetate phosphate citrate borate
(strong acids[HCl,H2SO4]/bases[NaOH] added to adjust pH) |
| Tear osmolarity |
| 302-318 mOsm/kg |
| Hypertonic products are 5% and treat corneal______ |
| Edema |
High viscosity causes____
Modifiers include____ |
irritation (cause blurring and crust forming) (reduce draining,inc retention rate)
[glycerin,cellulose derivs(hydroxyethylcellulose),polyvinyl alcohol, PEGs,carbomer]
|
| STerilize Solutions by |
HEAT or MEMBRANE FILTRATION
[add other sterilized excipients and bring to vol w/ sterile water ***if needed] |
| Suspensions require particle size less than ______ |
10 micrometers(smaller than oral susp) [reduces irritation and speeds dissolution] |
| Opthalmic susp used for |
to improve rx soluble
stay in cul de sac better/longer |
Antioxidant excipient:
Chelator:
Surfactant: |
Antioxidant excipient:Sodium metabisulfites
Chelator: EDTA disodium (inc act of BAC against P. aeruginosa)
Surfactant: Polysorbate(tween 80) 80 & tyloxapol [used as wetting agents for susp/red surf tension] |
| Droptainer/eyedrop packaging is dropper bottles.SIZE:___ |
5,10,15 and 30 mL sterilized before use |
semisolid eyedrops
ointments[base=white petrolatum] |
prolong contact time[good] [0.5% leaves per min cleared slowly]
blur vision
|
| sterilize ointment base _____ |
with heat then filter with molten
used frequently following surgery
[3.5 g is standrard tube] |
| Gels use ____ for gel forming |
cellulose derivatives(carbomers or gums)
Akten prolong contact time |
| Akten is a gel opth |
| high viscosity slowing removal |
| Ciloxan |
Ciprofloxacin HCl
used for Bacterial Keratitis,conjuctivitis
|
thimerisol is
|
| preservative |
