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)