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Drew 924 > Ophthalmic Delivery > Flashcards

Ophthalmic Delivery Flashcards

(58 cards)

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1
Q

What are the disadvantages for ophthalmic delivery?

A

1) sterility
2) poor retention
3) local ADRs

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2
Q

What are the desired characteristics of an ophthalmic product?

A

1) good penetration
2) easy admin
3) few ADRs

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3
Q

How are tears drained?

A

zipper like motion to superior & inferior punctum –> lacrimal duct

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4
Q

What is the normal rate of tear production?

A

1 - 25 uL/min

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5
Q

What is the normal tear volume?

A

10 - 20 uL

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6
Q

What is the pH range & mean in the eye?

A

5.2 - 8.3 (7.4)

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7
Q

What molecules provide buffering in the eye?

A

bicarb & proteins

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8
Q

What is the protein concentration in tears?

A

5.4 mcg/mL

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9
Q

What proteins are present in tears?

A

1) primarly lysozyme
2) dehydrogenases
3) amylase
4) esterase
5) albumin
6) immunoglobulins

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10
Q

What is the osmotic concentration in a tear?

A

310 - 350 mOsm

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11
Q

When is pH decreased?

A

1) awakening

2) secretions

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12
Q

How is dry eye measured?

A

Schirmer test

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13
Q

What drug properties induce tearing?

A

1) pH away from 7.4
- -alkali is worse
2) osmotic concentration not 310
- - hyper is worse
3) large particle size

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14
Q

How does conjunctival surface area relate to that of the cornea?

A

17x more area in conjunctiva

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15
Q

What conjunctival factors stimulate tearing?

A

pressure receptors

– dust, rubbing

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16
Q

What is the main barrier for drug delivery to the anterior chamber?

A

the cornea

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17
Q

Describe the hydrophobicity/hydrophilicity of the epithelium.

A

HYDROPHOBIC

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18
Q

Describe the hydrophobicity/hydrophilicity of the stroma.

A

HYDROPHILIC

– 70 % water

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19
Q

Describe the hydrophobicity/hydrophilicity of the endothelium.

A

thin & HYDROPHOBIC

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20
Q

What is the rate-limiting barrier for log K < 1

A

epithelium

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21
Q

What is the rate-limiting barrier for log K = 1-2.5?

A

endothelium

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22
Q

What is the rate-limiting barrier for log K > 2.5?

A

stroma

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23
Q

When would faster membrane transport be expected?

A

inflammation of that membrane

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24
Q

Which corneal layer contains efflux pumps?

25
What are Lipinski's ORAL rules of 5?
1) MW > 500 Da 2) H donors > 5 3) H acceptors > 10 4) log K > 5
26
What are Lipinski's CORNEAL rules of 5?
1) MW > 500 Da 2) H donors > 3 3) H acceptors > 8 4) log K > 4.2
27
Describe the log K of epinephrine.
low! hydrophilic
28
How is epinephrine's permeability increased for ophthalmic delivery?
ester increases permeability | -- esterase converts prodrug
29
What are the post-corneal factors for drug delivery to the eye?
1) metabolism | 2) iris adsorption
30
How is viscosity increased for delivery?
1) ointments 2) polymer inclusion 3) self-gelling systems
31
What polymers are used to increase viscosity?
1) PVA | 2) methylcellulose
32
What substances are used in self-gelling systems?
1) tromethamine | 2) gellan gum
33
What molecules do self-gelling systems depend on in the eye?
divalent cations in the tear film
34
How is residence time increased (other than viscosity alteration)?
1) non-erodible techniques - - Ocusert or implant 2) erodible techniques - - implant 3) sterile dressing
35
Describe the components of ocusert.
1) reservoir 2) ethylene acetate RCM 3) visibility ring
36
Describe the application of ocusert.
Inserted 1 x/wk
37
Describe 2 erodible products used to increase residence time.
1) Lacrisert (lower eyelid implant) | 2) Ozurdex (intravitreal implant)
38
What is Lacrisert for?
dry eye
39
What is the polymer in Lacrisert?
HPMC
40
How is Ozurdex implanted?
surgically (intravitreal)
41
Describe the structure of collagen.
alpha-helix of 3 polypeptide chains - - 1/3 glycine, 1/4 proline - - hydrophilic
42
How is a collagen dressing drug released?
protease
43
How is degradation decreased for a sterile collagen dressing?
increased cross-linking
44
How can drug loss be minimized (drug delivery form)?
1) NODS | 2) application device for elderly
45
What is NODS
medicated tab w/ flag when film dissolves in tears | -- fast dissolution requires amorphous drug forms
46
What are preservative agents?
1) Benzalkonium chloride 0.01% 2) Chlorbutanol 0.5% 3) Phenylmecuric nitrate 0.004% 4) Methylparaben 0.1 - 0.2%
47
What are antioxidant agents?
1) EDTA 0.1% 2) Sodium bisulfite 0.1% 3) Sodium metabisulfite 0.1%
48
What is the cause of age-related macular degneration?
leaky blood vessel in the posterior chamber
49
What are Sx of macular degeneration?
1) blurred/distorted objects 2) straight lines appear wavy 3) poor low-contrast & glare vision
50
How is age-related macular degeneration treated?
Intravitreal injection
51
How is intravitreal injection administered?
< 1 mL via 27-30 gauge needle
52
What is the treatment prior to intravitreal injection?
1) povodine-iodine on the eyelids | 2) lidocaine
53
What is Fick's Law?
Flux = DAK/h * ∆C
54
What is Retisert?
erodible surgical implant for chronic posterior uveitis | delivers chronic steroid over 6 months
55
What is the polymer in Retisert?
PLGA (polyacticglycolic acid)
56
What is Ozurdex?
Dexamethasone in PLGA pellet
57
Why is Ganciclovir for AIDS-related CMV retinitis supplied in an implant?
Ganciclovir has - - poor bioavailability - - poor Lipinski prediction
58
Ganciclovir implant... erodible or not?
non-erodible

Drew 924 (16 decks)

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