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Equine Final Year > Ocular Pharmacology > Flashcards

Ocular Pharmacology Flashcards

1
Q

A) What is the delivery volume for an eye drop?

B) How much is retained on the eye?

A

A) 50μl

B) 20μl

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2
Q

What is the issue of giving more than 1 drop? What can be done to help this?

A
  • >1 drop simulates reflex tearing and dilution effect!
  • Allow 10-15 minutes between administration of different topical drugs
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3
Q

Name 3 common topical anti-bacterials (5)

A
  • Fusidic acid
  • Chloramphenicol
  • Fluoroquinolones

–Ofloxacin

–Ciprofloxacin

•Aminoglycosides

–Neomycin

–Gentamycin

•Cloxacillin

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4
Q

Fusiidic Acid:

A) Where has it got goood activity?

B) What is it poor against?

A

A) Gram +ve activity, especially Staphylococcus sp which are common in eye

B) Against Chlamydophila felis and Pseudomonas sp

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5
Q

Name 2 posiitive of using fusidic acid? (4)

A
  • Good corneal penetration
  • Gel/drop formulation easy to use
  • Once daily dosing, good owner compliance
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6
Q

What is fusidic acid a good first line defence for?

A

Topical antibiotic for minor ocular surface infections e.g. conjunctivitis

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7
Q

Why can we not use fusidic acid for cornal ulcer in brachycephalic dogs?

A

Narrow spectrum

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8
Q

What is this?

A

Stromal ulcer

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9
Q

Chloramphenicol:

A) What spectrum?

B) What has it go poor efficacy against?

A

A) Broad including anaerobes

B) Against Chlamydophila felis and Pseudomonas sp

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10
Q

Name 2 positives of using chloramphenicol (4)

A
  • Good corneal penetration
  • Good choice for ocular surface disease, especially dogs, ocular surgery and penetrating corneal trauma
  • Low toxicity to corneal epithelium therefore good for corneal ulcers
  • Available in drops and ointment formulations
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11
Q

Name an example of a flueorquinolone (2)

A
  • Ofloxacin (Exocin®)
  • Ciprofloxacin (Ciloxan®)
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12
Q

Fluoroquinolone:

A) What is it effective?

B) What is it resistant against?

A

A) Effective against Gram-ve and some Gram+ve organisms

B) Some Staphylococcal sp and Streptococcal sp may be resistant

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13
Q

Aminoglycosides:

A) What is it effective against?

B) What is it commonly used for?

A

A) Gram-ve and some aerobic Gram+ve organisms

B) Pseudomonas sp

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14
Q

Name an example of an aminoglycoside (2)

A
  • Gentamycin (Clinagel®, Tiacil®)
  • Neomycin
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15
Q

What is neomycin often combined with?

A

Topical steroid

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16
Q

Name 2 problems of using gentamycin (aminoglycoside) (3)

A
  • Epitheliotoxic to corneal epithelium
  • Often irritan
  • Toxic to the epithelium
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17
Q

What i gentamycin (aminoglycoside) superseded by?

A

Fluoroquinolone

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18
Q

Cloxacilin:

A) What is it resistant to?

B) What is it commonly used for?

A

A) Beta-lactamase-resistant penicillin(bactericidal)

B) Topical antibiotic routinely used for infectious bovine keratoconjunctivitis (IBK); readily available

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19
Q

How do you do a subconjunctival injection?

Include needle type etc.

A
  • Injection of drug under bulbar conjunctiva
  • Slow release of drug, reduces labour intensity of treatment
  • Topical anaesthetic eye drops
  • 24-27 gauge needle
  • 0.5-1ml produces obvious ‘bleb’ at injection site
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20
Q

What is a subconjunctival injection commonly used for?

A

•Most common application is long-acting antibiotic in cattle

–IBK (infectious bovine keratoconjunctivitis)

–Penicillin G

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21
Q

Name 2 systemic anti bacterials useful to the eye (4)

A
  • Clindamycin
  • Tetracyclines
  • Sulphonamides
  • Enrofloxacin
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22
Q

Clindamycin:

A) What type of antibiotic?

B) What is the action?

C) What is it effective against?

A

A) Macrolide antibiotic

B) Bacteriostatic

C) Effective against Toxoplasma gondii, a cause of feline and canine uveitis

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23
Q

What is the treatment choice for feline chlamydial infection?

A

Doxycycline

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24
Q

Name a disadvantage of using tetracyclines e.g. Doxycycline (2)

A

Can discolour enamel of teeth in young animals

Can cause oesophagitis, essential to give with water

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25
Q

What is this?

A

Chlamydophila felis

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26
Q

What can sulphonamides cause and how?

A

•Can cause keratoconjunctivitis sicca (dry eye) due to toxic effect on lacrimal gland

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27
Q

Name 2 things which should be monitored when using sulphonamides

A
  • Monitor STT
  • Monitor tear production
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28
Q

What is the pharmacokinetics of using enrofloxacin (fluroquinolone) in cats?

A

Narrow therapeutic index

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29
Q

Name 2 issues of using fluroquinolones (3)

A
  • Can cause permanent blindness due to retinal toxicity
  • Rare but serious complication
  • Do not use in cats
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30
Q

Is equine or canine keratomyosis more common?

A

Equine

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31
Q

Why do anti viral drugs need to be applied 5-6 times a day?

A

They are virostatic

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32
Q

Name topical (2) and oral (1) treatments for Feline Herpes Virus 1

A

•Topical

–Ganciclovir 0.15% (Zirgan®)

–Aciclovir 3% ointment (Zovirax)

•Oral

–Famciclovir tablets

–Recommended dose varies frequently because of ongoing research; current dose is 90mg/kg bid

–Expensive but generic form now available

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33
Q

Name 2 extraocular immune mediated disease which will need to be treated with anti-inflammatory drugs (3)

A
  • Keratoconjunctivitis sicca (dry eye)
  • Feline eosinophilic keratoconjunctivitis
  • Chronic superficial keratitis (‘pannus’)
34
Q

Name a intraocular immune mediated disease which requires anti-inflammatory drugs

A

Uveitis

35
Q

Where are topical steroids contra-indicated? Why?

A

Corneal ulcers

–Steroids exacerbate collagenolysis, leading to corneal perforation

36
Q

What is dexamethasone good for?

A

Occular surface disease e.g. Pannus

37
Q

What is prednisolone acetate good for?

A

Intraocular disease e..g. uveitis

38
Q

What is the issue of usng topical NSAIDs with a corneal ulcer?

A

Epitheliotoxic and delay healing of corneal ulcers

39
Q

Name a time topical NSAIDs are good (2)

A
  • Uveitis
  • Intraocular surgery
40
Q

Name a topical NSAID (2)

A

•Ketorolac trometamol

–Acular®

–Most commonly used in general practice

•Flurbiprofen

–Ocufen®

41
Q

How does cyclosporine work?

A

T cell suppression (inhibit interleukin 2)

42
Q

Name 3 actions of cyclosporine (4)

A

•Increases tear production

–mainstay in the management of KCS (dry eye)

•Anti-inflammatory action

–Reduces scar tissue on ocular surface (corneal pigmentation and vascularisation)

  • Safe to use with corneal ulceration (even if a ‘dry eye’ ulcer is present)
  • Poor corneal penetration so suitable for ocular surface disease only
43
Q

Name immunomodulatory drugs and the action?

A
  • Calcineurin inhihibitors, reduce TH (T-Helper) lymphocyte activation
  • Ciclosporin
44
Q

What are immunomodulatory drugs first line treatment for?

A

Canine KCS

45
Q

What are the 2 ways anti-glaucoma drugs reduce pressure?

A

•Reduce aqueous humour production

OR

•Increase aqueous humour outflow

46
Q

How do carbonic anhydrase inhibitors work?

A

•Enzyme carbonic anydrase catalyses reaction in ciliary body to form aqueous humour

CO2 + H20 HCO3- + H+

•CAIs inhibit this reaction and therefore reduce the formation of aqueous humour which in turn reduces the IOP

47
Q

Why have systemic carbonic anhydrase inhibitors been superseded by topical CAI?

A

Due to the systemic side effects

48
Q

Name a Carbonic anhydrase inhibitors (CAIs) (2)

A
  • Dorzolamide
  • Brinzolamide
49
Q

Dorzolamide 2%:

A) What is it effective in?

B) What can we combine with?

C) Why dont we use in an emergency?

A

A) Dogs and cats

B) Anti-glaucoma

C) Doesn’t reduce pressure much

50
Q

Why is Brinzolamide 1% well tolerated?

A

Neutral pH

51
Q

A) How do adrenergic agents work?

B) What is the effect?

C) What is caused?

D) When do we NOT use it?

A

A) Beta block

B) Reduce aqueous humour

C) Miosis

D) Bradycardia

52
Q

Is prostglandin analogues ineffecive in cats and dogs?

A

Cats

53
Q

How do prostaglandin analogues work?

A
  • Reduces high IOP to safe level within 60-90 minutes of single application
  • Applied 1-2 times daily
54
Q

Where are prostaglandin analogues contraindicated and why?

A

•Contraindicated in uveitis and anterior lens luxation due to effect on pupil

–Uveitis – small pupil anyway

–Lens can get trapped in anterior chamber with a small pupil

55
Q

Name a prostaglandin analogue (2)

A
  • 0.004% travoprost (Travatan)
  • 0.005% latanoprost (Xalatan)
56
Q

What is the traditional first line treatment for glaucoma?

A

Osmotic diuretics

57
Q

What do osmotic diiuretics cause?

A

Renal and cardiac function

58
Q

What do osmotic diuretics do?

A

•Reduces IOP within 1hr and effect can last for up to 24 hours

59
Q

What are the 3 layers and the way in which tear substitutes work?

A
  • Aqueous layer → aqueous drops
  • Mucin layer → mucinomimetic
  • Lipid layer → lipid-based ointments
60
Q

What are tear substitutes often used in conjuction with?

A

Lacrimostimulant e.g. cyclosporine

61
Q

Name considerations when choosing a lubricant

A
  • Literally 100s available OTT
  • Drops vs gel vs ointment
  • Drops last <20mins
  • Gels last a few hours
  • Ointments last several hours
62
Q

Why cant we use aqueous tear substitues for?

A

•Canine KCS (keratoconjunctivitis sicca) generally too severe to make these drugs beneficial

63
Q

What are aqueous tear substitues good for?

A

Flushing thick ocular discharge from affected dry eyes

64
Q

What are aqueous tear substitutes?

A
  • Methylcellulose
  • Polyvinyl alcohol
  • Short-acting < 20mins
  • High frequency of administration
65
Q

Name 2 mucinomimetics (gels) (3)

A
  • Linear polymers (dextran, polyacrylic acid, polyinylpyrrolidone)
  • Carbomer 980
  • Viscoelastics (hyaluron derivative)
66
Q

What can we combine Mucinomimetics (gels) with?

A

Aqueous substitutes

67
Q

What is the minimum duration of Mucinomimetics (gels)?

A

4-6 hours

68
Q

What are Lipid-based tear substitutes
(ointments) good for?

A

Protection during GA and for dry eye management

69
Q

How ofteen do you apply Lipid-based tear substitutes
(ointments)?

A

1-4 x daily

70
Q

how do Lipid-based tear substitutes
(ointments) work?

A

Prevent evapoation of tear film

71
Q

Name a Lipid-based tear substitutes

(ointments) (3)

A

•Lanolin, petrolatum, mineral oil

72
Q

What do mydriatics do and when are they used?

A

•Mydriatics dilate the pupil

–Diagnostic purposes (examine lens, fundus)

–Therapeutic purposes (intraocular surgery, uveitis)

73
Q

What do cycloplegics do and when are they used?

A

•Cycloplegics relax ciliary body musculature

–Relieve painful ciliary spasm associated with anterior uveitis

–Therapeutic use only

74
Q

Tropicamide (Mydriacyl®):

A) What type of drug is it?

B) What is the effect?

C) What is the onset?

D) What is the main use?

A

A) Parasympatholytic drug

B) Mydriatic >> cycloplegic effect

C) Rapid onset (30 minutes) and short duration (8-12 hours)

D) Main use is for diagnostic purposes

75
Q

Atropine:

A) What type of drug is it?

B) What ar the effects?

C) What is the onset?

D) What iis the main onset?

A

A) Parasympatholytic drug

B) Mydriatic and cycloplegic effects

C) Slow onset (60 minutes) and long duration (60-120 hours)

D) Main use is for therapeutic purposes

76
Q

Name 2 side effects of atropine (3)

A

•Reduces tear production

–Care in animals with dry eye and brachycephalic breeds

•Raises IOP

–Contra-indicated in glaucoma

•Systemic effects

–Hypersalivation due to bitter taste

–Tachycardia, constipation (uncommon but care if low bodyweight)

–NB colic in horses

77
Q

What are local anaesthetic?

A

Weak bases that reversibly block afferent and efferent nerve impulses

78
Q

What are topical local anaesthetics used for?

A

–Diagnostic procedures

•E.g. tonometry, ocular ultrasound

–Minor surgical procedures

79
Q

Topical local anaesthetic:

A) How quickly does it act?

B) How long does it last?

A

A) Rapidly

B) Approx 30 minutes

80
Q

Name an occasion we do not use topical local anaestheitc (2)

A
  • Do not use therapeutically as epitheliotoxic i.e. delay corneal healing
  • Do not apply before STT as will block reflex tear production
81
Q

Name an injectable local anaesthetic and the use (2)

A

•Lignocaine (lidocaine, 1-2%) acts in 10 minutes and lasts 60 minutes

–Used for nerve blocks

•Bupivicaine (0.25-0.75%) acts in 45 minutes and lasts for 6 hours

–Used for post-operative analgesia

Equine Final Year (102 decks)

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