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Pharmaceutics Year 2 > Section 8 - Ophthalmics > Flashcards

Section 8 - Ophthalmics Flashcards

1
Q

What is an ophthalmic product?

A

Sterile dosage form free from foreign particles suitably compounded and packaged for instillation into the eye

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2
Q

Which dosage forms can ophthalmic products be?

A

Solutions, suspensions, ointments, emulsions, and some solid

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3
Q

What is the conjunctiva?

A

Membrane covering outer surface of the white portion of the eye and inner surface of eyelids

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4
Q

Which gland secretes tear film?

A

Lacrimal glands

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5
Q

What are tears made up of?

A

0.7% protein, electrolytes, and lysozyme

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6
Q

What is the purpose of tears?

A
  • Nutrition of cornea
  • Protection against bacterial infections
  • Removal of cellular debris and foreign matter
  • Formation of a continuous film over the cornea to produce a clear optical surface
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7
Q

How long does it take for tears to evaporate?

A

15-30 seconds

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8
Q

What are the 3 layers of the precorneal tear film and what is the function of each?

A

1) Superficial oily layer - consists of wax and cholesterol esters and slows evaporation
2) Middle aqueous layer - contains nutrients and lysozyme (thickest layer)
3) Adsorbed mucus layer - contains mucin and involved in adhesion of aqueous layer to cornea which keeps cornea wettable

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9
Q

What is the average tear volume?

A

7 uL

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10
Q

What occurs when tear volume is increased by instillation of an eyedrop?

A

Rapid reflex blinking restores volume back to normal

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11
Q

When an eyedrop is instilled, where does most of it go?

A

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

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12
Q

What can be done if nasolacrimal absorption is undesirable?

A

Use a smaller drop size

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13
Q

What volume do normal dropper tips provide?

A

25 uL

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14
Q

What makes topical ophthalmics different from topical skin products?

A

Topical ophthalmics must be manufactured as a sterile product and steps taken to ensure sterility

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15
Q

What is the drug dissolved in in an ophthalmic solution?

A

Isotonic medium containing antimicrobial preservative

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16
Q

When would an antimicrobial preservative not be needed in a ophthalmic solution?

A

If unit dose packaging is used

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17
Q

What do gel ophthalmics contain?

A

Viscosity-increasing agent in addition to the components used in a solution

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18
Q

How are gel ophthalmics usually packaged?

A

In ophthalmic ointment tubes

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19
Q

What do ophthalmic suspensions usually contain?

A

A suspending, and sometimes dispersing agents

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20
Q

What size of drug particles are best for ophthalmic suspensions?

A

Submicron size range

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21
Q

Most suspending agents used in ophthalmic suspensions are ____ derivatives, ___ molecular weight polymers or _____

A
  • Cellulose
  • High
  • Surfactants
22
Q

Care must be taken w/ surfactants to avoid ..?

A

Irritation and disruption of the precorneal tear film

23
Q

What do ophthalmic ointments contain?

A

Micronized drug dispersed in a petrolatum or other non-aqueous base

24
Q

How are ophthalmic ointments packaged?

A

In lined metal tubes or plastic-foil laminated tubes

25
Q

Which antimicrobial preservatives are effective against Pseudomonas species?

A

Benzalkonium chloride in combination w/ EDTA

26
Q

What are advantages to benzalkonium chloride?

A
  • Fast acting
  • Good stability and wide spectrum of activity
  • Stable over wide pH and temp ranges
27
Q

What is the usual concentration of benzalkonium chloride? What should the concentration never exceed?

A
  • Usual = 0.01%

- Never exceed 0.02% b/c will cause ocular discomfort

28
Q

When is thimerosal used as an antimicrobial preservative?

A

When incompatibilities preclude the use of benzalkonium chloride

29
Q

What is a disadvantage to thimerosal?

A

Slow acting and may cause sensitization and/or toxicity

30
Q

What is the usual concentration of thimerosal for ophthalmics?

A

0.01%

31
Q

Which parabens are used as ophthalmic preservatives and in what dosage form?

A
  • Usually methyl and propyl esters used in combination

- Most often used in ointments

32
Q

What is a disadvantage to parabens?

A

May cause burning sensation to eye

33
Q

What are the usual concentrations of parabens used in ophthalmics?

A
  • Methyl = 0.03-0.1%

- Propyl = 0.01-0.02%

34
Q

What happens if a product is irritating to the eye?

A

Tearing will result and contact time will be reduced

35
Q

What is the ideal buffer capacity for an ophthalmic product?

A

Adequate to maintain product, but low enough that when the product is instilled pH will rapidly adjust to 7.4

36
Q

Generally, buffer concentration for ophthalmics should not exceed ____

A

100 mM

37
Q

What is the function of viscosity increasing agents?

A

Increase contact time, reduce drainage rate, or enhance bioavailability

38
Q

Which viscosity increasing agents are commonly used in ophthalmic products?

A
  • Methylcellulose derivatives (hydroxypropylmethylcellulose, hydroxyethylcellulose, methylcellulose)
  • Carbomers
  • Polyvinyl alcohol
39
Q

Why do you want an ophthalmic product to be isotonic?

A

To avoid ocular discomfort

40
Q

What is the most common tonicity adjusting agent used in ophthalmic products?

A

Sodium chloride

41
Q

When is sodium chloride not used as a tonicity adjuster and what would replace it?

A
  • Glycerol or sugar

- Used when an ionizable tonicity adjuster will disrupt dispersive action of surfactants in the product

42
Q

What is the most common antioxidant used in ophthalmic products?

A

Sodium bisulfite

43
Q

Can pH be lowered in an ophthalmic product to prevent oxidation?

A

No b/c of the sensitive nature of eye tissues

44
Q

What does surfactant selection depend on?

A

Potential to irritate the eye, damage cell membranes or disrupt precorneal tear film

45
Q

Which surfactants are the only type suitable for ophthalmic products?

A

Non-ionic surfactants

46
Q

What concentration of surfactant should be used for ophthalmic products?

A

As low as possible, but usually around 0.1%

47
Q

What is the most common ointment base for ophthalmic products?

A

White petrolatum w/ mineral oil

48
Q

____ drug particles must be used for ophthalmic ointments

A

Ultra-fine

49
Q

How are ophthalmic ointments usually preserved?

A
  • W/ parabens
  • Products w/ broad spectrum antibiotics do not require antimicrobial agents if the product meets an appropriate microbial challenge test
50
Q

For which products is the USP preservative effectiveness test not required for?

A

Products made w/ anhydrous non-aqueous vehicles

Pharmaceutics Year 2 (17 decks)

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