Opthalmics

Question 1

What is the conjunctiva and corneal surfaces lubricated by?

Answer 1

• they are lubricated by a thin film of liquid (pre corneal tear film) secreted by the lacrimal glands

Question 2

What are the additional components of tears?

Answer 2

0.7% protein, electrolytes and lysozyme

Question 3

Why are tears necessary to the eye?

Answer 3

tears are necessary for the nutrition of the cornea, protection against bacterial infections, removal of cellular debris and foreign matter and the formation of a continuos film over the cornea to product a clear optical surface

Question 4

What are the 3 layers of the pre corneal tear film?

Answer 4

1) Superficial oily layer
- consists of wax and cholesterol esters and it functions to slow evaporation
2) Middle aqueous layer - contains nutrients and lysozyme
3) adsorbed mucous layer- contains mucin and is involved in adhesion of the aqueous layer to the cornea which keeps the cornea wettable

Question 5

What is the average tear volume?

Answer 5

7 microliters

Question 6

What happens to most of the eyedrop when it is placed in the eye?

Answer 6

Goes through the lacrimal drainage system and systemic absorption of the components may occur through the membranes of the nasolacrimal duct

Question 7

What can be done if systemic absorption of eyedrops is not desirable?

Answer 7

use a smaller drop size

Question 8

What volume do normal dropper tips dispense?

Answer 8

provide about 25 micrometers but specialized tips can provide about 10 microliters

Question 9

Topical ophthalmics must be manufactured as a _____

Answer 9

sterile product

Question 10

What are the dose forms generally used in the eye?

Answer 10

Solutions, suspensions, gels, ointments, emulsions and some solid products

Question 11

Describe ophthalmic solutions?

Answer 11

• drugs dissolved in an isotonic medium containing an antimicrobial preservative
• can be buffered but all products must be sterile
• administration via blunt dropper or a plastic container with a dropper tip

Question 12

Describe ophthalmic gels?

Answer 12

contain a viscosity increasing agent in addition to the components used in a solution
- usually packaged in ophthalmic ointment tubes

Question 13

Describe ophthalmic suspensions

Answer 13

• contain a suspending and sometimes dispersing agents
• suspended drug particles in the sub micron size range for ocular comfort, bioavailability and dispersibility
• most of the suspending agents are cellulose derivatives, high molecular weight polymers or surfactants
• care must be taken with surfactants to avoid irritation and disruption of the pre corneal tear film

Question 14

Describe ophthalmic ointments

Answer 14

• contain micronized drug dispersed in a petrolatum or other non-aqueous base
• they are packaged in lined metal tubes or plastic-foil laminated tubes

Question 15

Are there many or few preservatives available to those wanting to put a preservative in an ophthalmic product?

Answer 15

few

Question 16

What is benzalkonium chloride commonly used with as a preservative?

Answer 16

• used in combination with EDTA to giver better activity against pseudomonas species

Question 17

What are some of the benefits of benzalkonium chloride?

Answer 17

fast acting with good stability and wide spectrum of activity

• stable over wide pH and temperature ranges
• surfactant properties aid in corneal penetration of the drug

Question 18

What is the usual concentration of benzalkonium chloride?

Answer 18

• usual concentration is 0.01% and should never exceed 0.02% as this will cause ocular discomfort

Question 19

What does thimerosal have in it?

Answer 19

Mercury

Question 20

When is thimerosal usually used?

Answer 20

when incompatibilities preclude the use of benzalkonium chloride

Question 21

Is thimerosal fast acting or slow acting?

Answer 21

slow acting and may cause sensitization and toxicity

Question 22

What is the usual concentration of thimerosal for ophthalmics?

Answer 22

0.01%

Question 23

___ and ___ esters are used in combination and are most often used in ointments

Answer 23

methyl and propyl

Question 24

What is the usual concentration of methyl and propyl esters?

Answer 24

methyl: 0.03-0.1%
propyl: 0.01-0.02%

Question 25

pH of a solution with affect the chemical ___, ____ and _____

Answer 25

stability, solubility and ocular comfort

Question 26

What are the 2 reasons that ocular comfort is important when selecting a buffer?

Answer 26

import for compliance and if the product is irritating the tearing that is associated will result in a decreased contact time

Question 27

Buffer concentration should not exceed what value?

Answer 27

100 mM

Question 28

What is the function viscosity increasing agents? What is commonly used?

Answer 28

- increase contact time, reduce drainage rate and enhance bioavailability - methylcellulose derivatives, crabbers and polyvinyl alcohol are all commonly used

Question 29

What do we want to tonicity of the ophthalmic product to be? Why do we want this?

Answer 29

- we want the product to be isotonic to avoid ocular discomfort (this can lead to poor compliance and washout)

Question 30

What is generally used as a tonicity adjuster?

Answer 30

sodium chloride (sometimes glycerol or sugar is added)

Question 31

What is the most common antioxidant in ophthalmic products? What other ones are used?

Answer 31

- sodium bisulfite | - other antioxidants used are acetylcysteine, ascorbic acid and sodium thiosulfate

Question 32

Non ionic surfactants are the only type suitable for ophthalmic products- true or false

Answer 32

True

Question 33

What is the general concentration range for surfactants?

Answer 33

0.1%

Question 34

What is the most common base for ointments?

Answer 34

white petrolatum with mineral oil | sometimes liquid petrolatum/polyethylene combinations have been used

Question 35

What are ophthalmic ointments typically preserved with?

Answer 35

they are typically preserved with parabens - those containing broad spectrum antibiotics do not require antimicrobial agents if the product meets an appropriate microbial challenge test

Question 36

The USP preservative effectiveness test is not required for what products?

Answer 36

for anhydrous non-aqueous vehicles

Question 37

List the antibacterial preservatives

Answer 37

``` benzalkonium chloride benzethonium chloride chlorobutanol phenylmercuric acetate phenylmercurinic nitrate thimerosal ```

Question 38

List the antioxidants

Answer 38

sodium bisulfite sodium metabisulfite thiourea ethylenediaminetetraacetic acid

Question 39

List the wetting/clarifying agents

Answer 39

- polysorbate 80 | - polysorbate 20

Question 40

List the viscosity agents

Answer 40

- polvinyl alcohol - polyvinylpyrrolidone - methylcellulose - hydroxypropyl methylcellulose - hydroxyethylcellulose