dosage forms or Preparations of Ophthalmic solutions Flashcards
dosage forms or preparations of Ophthalmic solutions:
Aqueous Solution (eye drops)
Oily Solution
Colloidal solution
Ointment & cream
Dye impregnated paper strip
Ophthalmic disc or tablet (lamellae)
Ocusert
Therapeutic soft contact lens (TCL) or Bandage SCL
Collagen shields
Spray
normal Tear volume and (basal tear flow):
7uL
basal tear flow: 1 uL/min
Tear volume at cul-de-sac:
20-30 uL
maximum bioavailability of eyedrops:
20 uL
tear turnover/tear outflow at lacrimal passage:
non-irritated eye: 15% per min
after 1 eyedrop: 30% per min
80% of eyedrops egress through ______ not into eye
Tear ducts
egress of eyedrops through tear ducts can be decreased with:
punctal occlusion
decrease from 80% to 65%
interval before the next eyedrop to prevent egress of the medication:
5-10 mins
ways to instill ophthalmic solution (eye drops):
- Tilt the head back and look at the ceiling
- Retract the lower eyelid down and away from the eyeball or pinch and retract the lower eyelid
- Ask the patient to look upward
- Instill one drop into the exposed cul-de-sac. Be sure the TIP should NOT touch the eyelashes/eyelids
- Gently close the eyelid for 5 mins
ways to prolong contact time of topical solution:
- Retract the lower eyelids to create a pocket and increase the capacity of the cul-de-sac
- Close the eyes after instillation for 5-10 mins (DO NOT BLINK)
- apply pressure on the lacrimal sac
- Gently massage the eyeball with close eyelids
ways to instill ophthalmic OINTMENT:
- pull the lower eyelid down to create a pocket
- Place a small ribbon of ointment (about ¼ inch) into cul-de-sac
- Close the eyelids for a minute
- Eye massage
increases solubility of hydrophilic drugs by altering permeability of corneal epithelial membranes
SURFACTANT
determines ionization of a drug
pH
ionized portion (water soluble) of solution/drops will be more stable in:
Tears and Corneal Stroma
if the pH of the solution is made more basic, it increases:
Lipid solubility and Increases Epithelial Penetration
this increases drug contact time on the cornea:
Viscosity
a well known contaminants of Fluorescein Dye:
Pseudomonas Aeruginosa
known to invade or contaminant of Home made saline solution:
Acanthamoeba
added to solutions/eyedrops to prevent contamination:
Preservatives
Increases effectiveness of other preservatives:
Chelating Agents (EDTA)
Neutral pH of eyes (Tear film):
7 - 7.4 pH
since pH of the Tears is slightly alkaline, many ocular drugs are ______
Alkaloids (Weak bases)
helps maintain a comfortable pH:
Buffering Agents (weak acid w/ salts)
most common Buffering agent:
Boric acid w/ salt
relative measure of osmotic pressure between 2 solution:
Tonicity
Osmosis is movement of water from ______ to ______ concentration of solute
LOWER to HIGHER
ideal Isotonic solution:
0.7% - 1.5% NaCl
or
0.6% - 1.8% NaCl
hypotonic solution:
< 0.5% hypotonic
Hypertonic solution:
>2% hypertonic
Hypotonic solution is not harmful to ______eyes
it enhances drug corneal penetration
but it is harmful ________
External eyes
to Corneal endothelium (Intraocularly)
In KCS _____ solution is given if tears are ______
Hypotonic
Hypertonic
5% NaCl reduces:
corneal edema & conjunctival edema
10% NaCl causes permanent _______ damage
Corneal damage
Classes of Preservatives and example:
Bacteriostatic - Thimerosal
Bactericidal - BAK
mercuric compound and causes sensitivity and BAND keratopathy
Thimerosal
BAK acts as ______ and ______ agent
preservative and wetting agent
used with lipid INSOLUBLE drugs
to enhance penetration by breaking corneal barrier
ex: carbachol
BAK
Limited use because it is rapidly destroyed by water
Examples of Oily solution:
Diisoprpyl fluorophosphate DFP
Used for delivery of drugs not readily dissolved in water
Suspension
Example of Suspension drug:
Prednisolone acetate
made of high viscosity acrylics
slow release drug at steady level at overall lower concentration
less systemic side-effects
Gel
Examples of Gel:
Pilocarpine & Timolol
disadvantage of Gel form solution:
Blurring of Vision
has semi-solid vehicle which is lipid soluble
melts when it comes in contact with the eyes
Ointment
disadvantage of Ointment:
Increase allergic reaction
delay wound healing
Blurring of vision
semisolid vehicle which is water miscible
not applied on cul de sac because it will dissolve by tears & wash out
applied on skin of eyelids
Cream
examples of cream drug:
Betamethasone
used to prevent pseudomonas infection:
Dye Impregnated paper strip
rarely used,
placed at inferior cul-de-sac
Ophthalmic Tablet or disc (lamellae)
preservative free pellet with 5 mg of hydropropyl cellulose
used for mucus tear deficiency
Lacrisert
small, ovoid, flat of double-layered hydrophilic plastic
encloses the active ingredient of Drug
Ocusert
Examples of Ocusert:
Pilo 20 - releases 20ug/hr. for 7 days
Pilo 40 - releases 40ug/hr. for 7 days
(TREATMENT FOR GLAUCOMA)
soft contact lens soaked with drugs:
Therapeutic CL - TCL
or
Bandage SCL
examples of TCL:
NSS
5% NaCl
similar to TCL except collagen shields slowly dissolves increasing the concertation of drugs w/n the cornea for 1st few hrs
Collagen shields
Advantage of TCL and Collagen shields:
- Act as drug reservoir
- Increase contact time (prolong effect)
disadvantage of TCL and Collagen shields:
Bacteria binds to contact lens - possible ocular infection
advantage of Spray as mydriatic or cycloplegic agents:
Less irritation
