Ocular Systems

Question 1

What are common eye conditions?

Answer 1

*allergies
*blepharitis
*cataract
*conjunctivitis
*dry eye
*glaucoma

Question 2

What are physiological barriers of the eye?

Answer 2

*cornea
*sclera
*tear production/blinking- eye drops removed faster
*protein binding/drug metabolism

Question 3

What is the precorneal volume?

Answer 3

7uL, volumes of 20-30uL can be held before spillage occurs

Question 4

What physiochemical drug properties should be considered when designing ophthalmics?

Answer 4

*solubility- lipophilicity
*molecular size and shape
*charge
*degree of ionisation

All affect RATE and ROUTE of permeation into cornea

Question 5

What are the two ways that ophthalmics travel into the eye?

Answer 5

*passive diffusion- transcellularly (lipophilic) or paracellularly (hydrophilic)- both lipophilic and hydrophilic drugs permeate better
*carried mediated active transport-

Question 6

Does ionised or unionised form permeate lipid membranes of eye easier?

Answer 6

Unionised

Question 7

Is the corneal epithelium positively or negatively charged and do cationic or anionic drugs permeate better?

Answer 7

Negatively and cationic drugs

Question 8

What size do particles have to be for ophthalmic drugs?

Answer 8

<500 daltons

Question 9

Why is chemical form of a drug important in ophthalmics?

Answer 9

Changing salt affects solubility and lipophilicity of drug

Question 10

How do you fix drugs that don’t meet the desired physiochemical properties?

Answer 10

Use prodrug (converted enzymatically or chemically to parent drug in eye)

Question 11

What are advantages of using solutions (eye drops)?

Answer 11

*high solution conc can be achieved
*easy to manufacture
*provide better dose uniformity and ocular bioavailability

Question 12

What is a disadvantage of using solutions?

Answer 12

Rapidly drained from eye

Question 13

How can the rapid clearance of drug solutions be fixed?

Answer 13

*add viscosity increasing agents to increase tear viscosity
*eg hydroxyethylcellulose

Question 14

What are water based gels?

Answer 14

Contain polymers so that they are liquid upon administration but gel on contact with eye- increase retention times

Question 15

Why is there a phase change in water based gels?

Answer 15

*change in temp on contact
*change in pH
*change in ionic strength in tear film

Question 16

What is an advantage of using water based gels?

Answer 16

*ease of administration
*improved patient compliance

Question 17

Why would suspensions be used for drug delivery?

Answer 17

*for poorly water soluble drugs
*drugs with poor aqueous stability

Question 18

What is an advantage of using suspensions?

Answer 18

Prolonged residence time of drug in eye, allowing time for dissolution in years - increased ocular bioavailability

Question 19

What are disadvantages of using suspensions in eye drug delivery?

Answer 19

*instability issues- dose uniformity, increased particle size with time
*possibilities of degradation during sterilisation process of suspension

Question 20

What part of the eye are ointments applied to?

Answer 20

Conjunctiva

Question 21

When are ointments applied and why?

Answer 21

Nighttime- can cause blurred vision

Question 22

What should be considered when choosing packaging for ophthalmics?

Answer 22

*are materials compatible with formulation and ensure product stability?
*can sterility be achieved and assured for entire shelf life
*do materials meet pharmacopoeial and regulatory standards?
*are containers tamper evident?
* does it offer ease of administration to patient ?

Question 23

What are the critical quality parameters for ophthalmics?

Answer 23

Ophthalmics are required to:
-be sterile up to point of use
-must comply with pharmacopoeial tests for sterility

Question 24

What type of sterilisation should be used for ophthalmics?

Answer 24

Terminal sterilisation

Question 25

What are excipients used for in ophthalmics?

Answer 25

To improve tolerability and compliance

Question 26

What pH range can eye tolerate?

Answer 26

3.5-9 (7.4 preferred)
Any other- eye irritation

Question 27

If pH manipulation fails to increase drug solubility, what is the next step?

Answer 27

*Add solubility enhancing materials (glycerin)
*if desired aqueous solubility not achievable, consider oily solution or emulsion

Question 28

Why is too high of a viscosity not well tolerated in the eye?

Answer 28

Drug diffusion inhibited
Hard to administer

Question 29

What is an example of an ophthalmic antimicrobial preservative?

Answer 29

Methylparaben

Question 30

How are ophthalmics sterilised?

Answer 30

*autoclaving- manufactured and packaged under clean conditions followed by sterilisation- moist-heat sterilisation
*filtration- through a circa 1um filter
*production under aseptic conditions- dispersion of sterile therapeutic agent into sterile vehicle and packaging

Question 31

How do contact lenses work?

Answer 31

Polymers that correct Vision issues from refractive error

Question 32

What is a complication that can arise from contact lenses?

Answer 32

Microbial keratitis

Question 33

What are the functions of contact lens solutions?

Answer 33

*soaking- disinfects, maintains hydrated stats (NaCl)
*(re)wetting- hydrates lens, deals with contamination, lubricates (NaCl)
*cleaning- removed ocular debris, dust and bacteria (NaCl)