Ocular

Question 0

Current practice to prevent these problems?

Answer 0

Frequent instillations of eyedrops.

Question 1

Dis of ocular administration? (5)

Answer 1

Low BA of ophthalmic drugs because of eye’s protective mechanism:
1.tight junctions in the epithelium and cornea
and betwen the cells esp the basal cells.this acts as a barrier.
2. Conea has low permeability to drugs and prevents rapid absorption of drugs.
3. Eyelid shear rate blinking is high
4.Baseline and reflex lacrimation.
5.Drainage removes the drug.

Question 2

Problem of frequent use

Answer 2

Leads to cellular damage and toxic effects!

Question 3

Describe 3 strategies to solve the problem of BA of ophthalmic drugs.

Answer 3

1. Apply in situ gelling systems or phase transition systems.
   We instill the drug in a liquid form. PH of the eye triggers a phase transition. The drug becomes solid or gel in the cul de sac.
2. Viscous semi-solid preparation. Gels and ointments have a sustained contact with eye.DIS: sticky. Blurred vision= more blinking reflex.
3. Water soluble Ploymers : to increase contact time and penetration. DIS : blinking rate high.
4. Mucoadhesive Concept : increase resisdance time.interacts with mucus and eye tissues.

Question 4

List 5 polymer- related factors that influence mucoadhesion

Answer 4

1. Hydration or degree of swelling
2. Concentration
3. Functional groups
4. Molecular weight
5. Molecular conformation or chain flexibility & mobility

Question 5

Why is hydration important for muco adhesion?

Answer 5

Because the more it is hydrated,the more it will swell,the more it will have polymer to water interactions instead of polymer to polymer interactions.

Question 6

Elaborate on the MW aspect for muco adhesion

Answer 6

MW should be a minimum of 100,000Da for there to be muco adhesion.

Question 7

Elaborate on chain flexibility

Answer 7

Greater chain flexibilty leads to greater mobility leads to greater interpenetration of the chains into the mucus leads to greated retention of the chains.

Question 8

Elaborate on the different functional groups

Answer 8

Capable pf forming H bonds and not crossing the biological membranes

Question 9

Example of a neutral polymer

Answer 9

Cellulose.has only OH groups to form H bonds. No electrostatic bonds.

Question 10

Which one is stronger?

Electrostatic or hydrogen !

Answer 10

Electrostatic