L2 OCULAR DRUG DELIVERY (MCQ)

Question 1

what are the 4 modes of drug delivery into the eyes?

Answer 1

topical: Drop, ointment, gel, SCL
periocular: subconj, subtenon, peribulbar, retrobulbar
intraocular: intracameral, intravitreal
systemic: oral, intravenous, intramuscular

Question 2

WHAT ARE THE 7 FACTORS AFFECTING LOCAL OCULAR DRUG
PENETRATION

Answer 2

1. Drug tonicity: effects of osmotic pressure
2. molecular weight an size
3. Drug concentration and solubility: higher concentration, improved
   penetration
4. viscosity : methylcellulose and polyvinyl alcohol makes drugs ‘thicker’ and increases the contact time with the cornea
5. Surfactants: preservatives may alter cell membrane in the cornea
   and increase drug permeability eg. Benzalkonium
6. pH: tears pH7.4, different pH may cause reflex tearing
7. Lipid solubility: higher lipid solubility, improved penetration
   * Amphipathic: epithelium
   * Lipophilic: endothelium
   * Hydrophilic: stroma

Question 3

most common form of topical eye drugs? pros and cons? how to improve absorption?

Answer 3

Eye drops
* Usually most preferred method
* convenient
-easy to use
-absorption reduced.
* 1 drop ~50microlitre, conjunctival sac ~5-15 microlitre

• To improve absorption: compress lacrimal sac to close eyes
• 50% of drug remains after 4mins of instillation
• 10% of drug reaches aqueous humor

Question 4

what is the pros and cons of topical eye ointments?

Answer 4

Increase contact time of medication on ocular surface

causes blurring of vision

Question 5

where is periocular injections done? what is good about this route of drug delivery?

Answer 5

Reaches behind iris-lens
* subconj: underneath the conjunctiva, drugs that cannot
penetrate the cornea, therefore, introduce via sclera, allow higher
concentration to reach target site.

• Subtenon: anterior subtenon- diseases anterior to the lens
  posterior subtenon- disease posterior to the lens
• Peribulbar: around the equator of the eye ball–optic neuritis, posterior uveitis, anaesthetic
• Retrobulbar: in the orbit further back behind the eye ball, which is near the optic nerve–Anaesthetics

pros:
* Bypasses the conjunctiva and corneal epithelium, good for drugs with low lipid solubility
* Good for steroids & local anesthetic

Question 6

what are the 2 types of intraocular injections?

Answer 6

Intravitreal OR intracameral

• Intravitreal: into the vitreous
• Eg. Anti-VEGF for conditions like diabetic retinopathy
• Eg. Steroids: macular edema
• Intracameral: into a chamber
• Cataract surgery