Ocular Pharmacology Flashcards by Anna Burrows

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

B) How much is retained on the eye?

A) 50μl

B) 20μl

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

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

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Name 3 common topical anti-bacterials (5)

Fusidic acid
Chloramphenicol
Fluoroquinolones

–Ofloxacin

–Ciprofloxacin

•Aminoglycosides

–Neomycin

–Gentamycin

•Cloxacillin

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Fusiidic Acid:

A) Where has it got goood activity?

B) What is it poor against?

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

B) Against Chlamydophila felis and Pseudomonas sp

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Name 2 posiitive of using fusidic acid? (4)

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

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What is fusidic acid a good first line defence for?

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

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

Narrow spectrum

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What is this?

Stromal ulcer

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Chloramphenicol:

A) What spectrum?

B) What has it go poor efficacy against?

A) Broad including anaerobes

B) Against Chlamydophila felis and Pseudomonas sp

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Name 2 positives of using chloramphenicol (4)

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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Name an example of a flueorquinolone (2)

Ofloxacin (Exocin®)
Ciprofloxacin (Ciloxan®)

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Fluoroquinolone:

A) What is it effective?

B) What is it resistant against?

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

B) Some Staphylococcal sp and Streptococcal sp may be resistant

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Aminoglycosides:

A) What is it effective against?

B) What is it commonly used for?

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

B) Pseudomonas sp

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Name an example of an aminoglycoside (2)

Gentamycin (Clinagel®, Tiacil®)
Neomycin

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What is neomycin often combined with?

Topical steroid

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

Epitheliotoxic to corneal epithelium
Often irritan
Toxic to the epithelium

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What i gentamycin (aminoglycoside) superseded by?

Fluoroquinolone

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Cloxacilin:

A) What is it resistant to?

B) What is it commonly used for?

A) Beta-lactamase-resistant penicillin(bactericidal)

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

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How do you do a subconjunctival injection?

Include needle type etc.

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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What is a subconjunctival injection commonly used for?

•Most common application is long-acting antibiotic in cattle

–IBK (infectious bovine keratoconjunctivitis)

–Penicillin G

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

Clindamycin
Tetracyclines
Sulphonamides
Enrofloxacin

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Clindamycin:

A) What type of antibiotic?

B) What is the action?

C) What is it effective against?

A) Macrolide antibiotic

B) Bacteriostatic

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

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What is the treatment choice for feline chlamydial infection?

Doxycycline

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

Can discolour enamel of teeth in young animals

Can cause oesophagitis, essential to give with water

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What is this?

Chlamydophila felis

What can sulphonamides cause and how?

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

Name 2 things which should be monitored when using sulphonamides

* Monitor STT * Monitor tear production

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

Narrow therapeutic index

Name 2 issues of using fluroquinolones (3)

* Can cause permanent blindness due to retinal toxicity * Rare but serious complication * Do not use in cats

Is equine or canine keratomyosis more common?

Equine

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

They are virostatic

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

•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

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

* Keratoconjunctivitis sicca (dry eye) * Feline eosinophilic keratoconjunctivitis * Chronic superficial keratitis (‘pannus’)

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

Uveitis

Where are topical steroids contra-indicated? Why?

Corneal ulcers ## Footnote –Steroids exacerbate collagenolysis, leading to corneal perforation

What is dexamethasone good for?

Occular surface disease e.g. Pannus

What is prednisolone acetate good for?

Intraocular disease e..g. uveitis

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

Epitheliotoxic and delay healing of corneal ulcers

Name a time topical NSAIDs are good (2)

* Uveitis * Intraocular surgery

Name a topical NSAID (2)

•Ketorolac trometamol –Acular® –Most commonly used in general practice •Flurbiprofen –Ocufen®

How does cyclosporine work?

T cell suppression (inhibit interleukin 2)

Name 3 actions of cyclosporine (4)

•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

Name immunomodulatory drugs and the action?

* Calcineurin inhihibitors, reduce TH (T-Helper) lymphocyte activation * Ciclosporin

What are immunomodulatory drugs first line treatment for?

Canine KCS

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

•Reduce aqueous humour production OR •Increase aqueous humour outflow

How do carbonic anhydrase inhibitors work?

•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

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

Due to the systemic side effects

Name a Carbonic anhydrase inhibitors (CAIs) (2)

* Dorzolamide * Brinzolamide

Dorzolamide 2%: A) What is it effective in? B) What can we combine with? C) Why dont we use in an emergency?

A) Dogs and cats B) Anti-glaucoma C) Doesn't reduce pressure much

Why is Brinzolamide 1% well tolerated?

Neutral pH

A) How do adrenergic agents work? B) What is the effect? C) What is caused? D) When do we NOT use it?

A) Beta block B) Reduce aqueous humour C) Miosis D) Bradycardia

Is prostglandin analogues ineffecive in cats and dogs?

Cats

How do prostaglandin analogues work?

* Reduces high IOP to safe level within 60-90 minutes of single application * Applied 1-2 times daily

Where are prostaglandin analogues contraindicated and why?

•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

Name a prostaglandin analogue (2)

* 0.004% travoprost (Travatan) * 0.005% latanoprost (Xalatan)

What is the traditional first line treatment for glaucoma?

Osmotic diuretics

What do osmotic diiuretics cause?

Renal and cardiac function

What do osmotic diuretics do?

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

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

* Aqueous layer → aqueous drops * Mucin layer → mucinomimetic * Lipid layer → lipid-based ointments

What are tear substitutes often used in conjuction with?

Lacrimostimulant e.g. cyclosporine

Name considerations when choosing a lubricant

* Literally 100s available OTT * Drops vs gel vs ointment * Drops last \<20mins * Gels last a few hours * Ointments last several hours

Why cant we use aqueous tear substitues for?

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

What are aqueous tear substitues good for?

Flushing thick ocular discharge from affected dry eyes

What are aqueous tear substitutes?

* Methylcellulose * Polyvinyl alcohol * Short-acting \< 20mins * High frequency of administration

Name 2 mucinomimetics (gels) (3)

* Linear polymers (dextran, polyacrylic acid, polyinylpyrrolidone) * Carbomer 980 * Viscoelastics (hyaluron derivative)

What can we combine Mucinomimetics (gels) with?

Aqueous substitutes

What is the minimum duration of Mucinomimetics (gels)?

4-6 hours

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

Protection during GA and for dry eye management

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

1-4 x daily

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

Prevent evapoation of tear film

Name a Lipid-based tear substitutes | (ointments) (3)

•Lanolin, petrolatum, mineral oil

What do mydriatics do and when are they used?

•Mydriatics dilate the pupil –Diagnostic purposes (examine lens, fundus) –Therapeutic purposes (intraocular surgery, uveitis)

What do cycloplegics do and when are they used?

•Cycloplegics relax ciliary body musculature –Relieve painful ciliary spasm associated with anterior uveitis –Therapeutic use only

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) Parasympatholytic drug B) Mydriatic \>\> cycloplegic effect C) Rapid onset (30 minutes) and short duration (8-12 hours) D) Main use is for diagnostic purposes

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) 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

Name 2 side effects of atropine (3)

•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

What are local anaesthetic?

Weak bases that reversibly block afferent and efferent nerve impulses

What are topical local anaesthetics used for?

–Diagnostic procedures •E.g. tonometry, ocular ultrasound –Minor surgical procedures

Topical local anaesthetic: A) How quickly does it act? B) How long does it last?

A) Rapidly B) Approx 30 minutes

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

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

Name an injectable local anaesthetic and the use (2)

•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