Ocular pharmacology

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chrisd
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4499
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Ocular pharmacology
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2010-01-27 16:28:59
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veterinary ocular eye pharmacology
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  1. Beta-lactam antibiotics
    Penicillins and cephalosporins

    Bactericidal block cell wall synthesis

    Intraocular penetration poor unless BOB inflammed

    May penetrate ant. chamber if corneal epithelium damaged

    Mostly G +'ve activity

    Aminopenicillins have increased G-'ve activity
  2. Sulphonamides
    Broad spec bacteriostatic

    Block Folic acid synthesis

    Good Ocular penetration

    Potential KCS

    Dobermann pinchers immune mediated polyarthritis
  3. Tetracyclines
    Broad spec bacteriostatic

    Bind 30S subunit of bacterial ribosomes and block AA attachment

    Systemically penetrate BOB poorly (except doxycycline)

    Topically applied may reach therapeutic concentration in ant. chamber

    Active against chlamydophila, mycoplasma, rickettsia, G-'ve and G+'ve

    Resistance common
  4. Aminoglycosides
    Bactericidal binds 30S subunit

    Systemically does not penetrate BOB

    Topically poor penetration

    Activity against G-'ve and some G+'ve

    Gentamicin used against pseudomonas

    Tobramycin broad spec and used if genta resistance

    Neomycin broad spec but poor penetration
  5. Macrolides and lincosamides
    Binds 50S subunit

    Erythromycin, tylosin, lincomycin, clindamycin ar bacteriostatic with predominantly G+'ve activity

    Newer Azithromycin is acteriocidal and broad spectrum

    Good tissue penetration

    Clindamycin effective against anaerobes
  6. Fluoroquinolones
    Broad spec bactericidal inhibiting DNA gyrase

    Liver metabolism (except baytril) with renal excretion

    • Good tissue distribution
    • Topical application achieves high ant. chamber concentration

    Effective against most G-'ve including pseudomonas

    Some activity against G+'ve

    Poor anaerobe activity

    • Enrofloxacin
    • - narrow therapeutic range with blindness from generalised retinal degeneration if given at a high dose
    • - some Staph and Strep resistance, ineffective against anaerobes
  7. Fusidic Acid
    Blocks binding of transfer RNA to bacterial ribosome inhibiting protein synthesis

    Good G +'ve and some G-'ve activity

    Good corneal penetration

    Carbomer gel vehicle in Fucithalmic
  8. Chloramphenicol
    Broad spectrum bacteriostatic

    Binds 50S subunit blocking protein synthesis

    • G -'ve, G+'ve, anaerobic activity
    • Chlamydophila (not as good as tetracycline), mycoplasma and rickettsia sensitive
    • Nocardia and Mycobacterium resistance

    High lipid solubility gives good intraocular penetration and can access the CNS
  9. Polypeptide antibiotics
    Bactericidal inhibiting cell wall synthesis.

    Toxic if given systemically

    Bacitracin G +'ve range

    Polymixin B G -'ve range

    Often combined
  10. Nitroimidazole
    Metronidazole bactericidal effective against anaerobes

    Good tissue penetration given systemically

    (Could be used in combination with cephalosporin to give aerobic cover)
  11. Antivirals
    (in orfer of decreasing efficacy):

    • Trifluorothymidine (most effective in vitro efficacy against FHV-1) requires application4-6 times daily
    • Idoxuridine
    • vidarabine

    bromovinyldeoxuridine

    acyclovir
    only product available in th UK

    Human interferon alpha 2 anecdotal reports of efficacy when applied topically

    L-lysine - in vitro observation that it inhibits viral replication in the presence of low arginine levels
  12. Antifungals
    Topical application for mycotic keratitis

    Systemic use for mycotic chorioretinitis

    No licenced products for animals in UK

    Itraconazole, ketoconazole, fluconazole, clotrimazole, amphotericin B
  13. Corticosteroids
    Glucocorticoids have minimal mineralocorticoid activity and powerful anti-inflamatory effect

    Anti-inflammatory action is to induce lipocortin (intracellular protein)

    Lipocortin inhibits phospholipase A2 (PLA2)

    PLA2 is an endogenous enzyme catalyses breakdown of cell membrane phospholipids to arachidonic acid

    Arachidonic acid is the precursor to proinflammatory leucotrienes and prostoglandins




    At higher concentrations glucocorticoids are immunosuppressive

    Contraindicated in corneal ulceration as it may exacerbate stromal collegenolysis 'melting'

    Long-term use in humans has been seen to lead to cataract development and glaucoma

    Medium term topical glucocorticoid administration caused a reversible increase in intraocular pressure.... and....

    Longer tx (7weeks) caused subcapsular cataract formation (experimental cats Zhan 1992)

    Topical tx causes reversible increase in IOP in experimental beagles (Gelatt and brooks 1999)

    Choice of topical product should depend on ability to penetrate into the eye

  14. Non-steroidal anti-inflammatories
    Inhibits cyclo-oxygenase pathway

    At least 2 isoforms of cyclo-oxygenase exist

    COX-1 inhibition may lead to side-effects (eg GI bleeding)

    COX-2 is induced at sites of inflammation.



    Used in postop pain relief and uveitis

    Contraindicated in anterior segment bleeding

    Ketorolac (Acular), Flubiprofen (Ocufen), Diclofenac (Voltarol Ophtha)
  15. Ciclosporin (Cyclosporin(e))
    Optimmune 0.2% ointment

    Multiple mechanisms of action

    Acts as a Tcell suppressor by inhibiting interleukin 2

    Induces production of transforming growth factor beta (TGF beta) which is a potent endogenous immunosupressant



    Does not penetrate the intact cornea well

    It can increase tear production in normal dogs, possibly via effects on a prolactin receptor (Kaswan 1989)

    Used to tx autoimmune KCS

    Can be effective for other immune mediated diseases (e.g. chronic superficial keratoconjunctivitis, plasmacytic conjunctivitis, episcleritis)

    Has been used for eosinophilic keratoconjunctivitis in cats and ERU in horses

    No evidence of systemic or ocular toxicity

    Recommmended that bacterial or viral infections are tx'd before use

    Can cause nephrotoxicity in humans

    Immediate discomfort of topical application is common

    Not advised to use within a 2 week period of live vaccines

    Topical irritation reported in dogs
  16. Aciclovir
    Zovirax 5% ointment

    Inhibits viral replication (viral DNA polymerase) - depends on viral thymidine kinase for phosphorylation

    Virostatic - unable to eradicate latent viral replication

    Ocular irritation may occur

    q4-6h for 3 weeks max

    Has been used in the management of FHV-1 infections

    In vitro studies suggest Aciclovir and human interferon combination to be more effective against FHV-1 than aciclovir on its own

    In vivo efficacy unknown
  17. Lysine
    Antagonises arginine, which is required for viral replication

    Has been used in the management of FHV-1 infection

    Limited clinical evidence regarding its efficacy in treating FHV-1

    25-500mg PO q12-24h
  18. Trifluorothymidine
    Trifluridine, F3T, Viroptic (USA) 1% solution

    Inhibits viral replication (viral DNA polymerase) - does not depend on viral thymidine kinase for phosphorylation

    Virostatic and is unable to eradicate latent viral infection

    Clinically the most useful antiviral for FHV-1

    Safe to combine with human interferon

    Short shelf life and expensive

    q4-6h for 3 weeks max
  19. Ciprofloxacin
    Ciloxan, Ciproxin 0.3% solution

    Bactericidal through inhibition of bacterial DNA gyrase

    Broad spec activity against most G-'ve and some G+'ve aerobes

    Some activity against Mycoplasma and Chlamydophila

    Active against Staphylococcus and Pseudomonas

    Increasing resistance against staphs and streps

    Should be reserved for 2nd line tx

    May cause local irritation

    q6h
  20. Fluorometholone
    FML

    Corticosteroid

    0.1% drops

    Phospholipase A2 inhibition (COX and lipoxygenase inhibition)

    Used to tx superficial inflammation or anterior uveitis, rarely used in veterinary ophthalmology

    Contraindicated in corneal ulceration and infectious keratitis

    Theoretically could induce higher intraocular pressure and cataract development with long-term use

    q6-12h
  21. Acetazolamide
    Diamox 500mg vial powder for reconstitution

    Systemic carbonic anhydrase inhibitor

    Reduces intraocular pressure by reducing aqueous humour production

    Inhibits bicarbonate ion formation within the ciliary body epithelium

    Can be used in acute cases, but topical carbonic anhydrase inhibitors are better

    Avoid in anorexic dogs, those with hepatic or renal dysfunction and those with sulphonamide hypersensitivity

    Cats are particularly sensitive

    May cause GI disturbances, anorexia, V+, D+, panting, metabolic acidosis, diuresis, electrolyte disturbances

    Dogs 5-10mg/kg iv, 4-8mg/kg PO q8-12
  22. Apraclonidine
    Iopidine 0.5% solution

    Topical alpha 2 selective agonist.

    Decreases aqueous humour production via inhibition of adenylate cyclase activity in the cilary body

    Used to reduce IOP in glaucoma

    Effect in dogs is inconsistant

    Prudent to measure heart rate before and after application

    Causes blanching of the conjunctival vessels, bradycardia and mydriasis in dogs

    Considered toxic in cats

    Do not use in dogs with uncontrolled cardiac disease
  23. Betaxolol
    Betoptic 0.25% or 0.5% solution

    Beta-1 selective beta blocker that decreases aqueous humour production

    Beta-adrenoreceptor blockade in the ciliary body

    Used in glaucoma management

    Can be used in combination with carbonic anhydrase inhibitor

    Avoid in uncontrolled heart failure and asthma

    Can cause miosis, conjunctival hyperaemia and local irritation

    q12h

    No information on the use in cats
  24. Brinzolomide
    Azopt 10mg/ml (1%)

    Carbonic anhydrase inhibitor

    Reduces IOP by reducing the rate of aqueous humour production

    Inhibits formation of bicarbonate ions in the ciliary body epithelium

    Used to control glaucoma

    May be better tolerated than Dorzolomide as it has a pH of 7.5

    Effective in dogs and cats

    Ineffective in normal cats

    Contraindicated in severe hepatic or renal impairment

    q8-12h
  25. Dorzolomide
    Trusopt 2%, Cosopt (2%+ 0.5% timolol)

    Carbonic anhydrase inhibitor

    Reduces IOP by decreasing aqueous humour production

    Inhibits the formation of bicarbonate ions within the ciliary body epithelium

    Used to control glaucoma in dogs and cats

    pH 5.6 - not tolerated as well as brinzolomide

    Effective in dogs and cats

    Causes miosis and therefore not to be used in concurrent uveitis / lens luxation

    Contraindicated in hepatic or renal impairment

    Can cause local irritation and blepharitis

    • Dogs q8h
    • Cats q 12h
    • Birds q12h
  26. Glycerol
    Glycerin(e) Glycerol 50% solution

    Lowers intraocular pressure by reducing aqueous humour production and improving aqueous humour outflow (secondary to reducing vitreous humour volume)

    Used in management of acute glaucoma

    Superceded by topical agents

    Maximal reduction in IOP 1 hour after administration.

    Will last for 10hours

    Induces less diuresis than mannitol

    Contraindicated in diabetes, dehydration and renal dysfunction

    Dogs and Cats: 1-2g/kg PO single dose
  27. Latanoprost
    Xalatan 0.005%

    Agonist for prostaglandin-F receptors

    Reduces IOP by increasing uveoscleral outflow

    Management of canine primary glaucoma

    Can have a profound effect on IOP in the dog

    Less predictable effect in cats

    Often used in conjunction with carbonic anhydrase inhibitors

    Miosis in dogs and cats, mild irritation of conjunctivae

    (Increased iridal pigmentation in humans - not seen in dogs)

    Contraindicated with uveitis and anterior lens luxation

    1 drop per eye given in the evening
  28. Pilocarpine
    Most common concentration is 1%

    Direct acting parasympathomimetic that stimulates cholinergic receptors

    Lowers IOP by causing ciliary body muscle contraction, miosis and improved humour outflow

    Used in the management of glaucoma

    Use has been superceded by CAIs and prostaglandin analogues

    Oral dosing increases lacrimation and can be used in neurogenic KCS

    Produces miosis in 10-15min for 6-8hrs

    Potentially toxic in the cat

    Avoid in uveitis and anterior lens luxation

    Can cause conjunctival hyperaemia (vasodilation) and local irritation from low pH

    (Signs of systemic toxicity: hypersalivation, V+, D+, cardiac arrhythmias

    1 drop 1% per 10kg PO q12h with food
  29. Timolol maleate
    Timolol, Timoptol, [CoSopt (combined with dorzolamide)]

    Topical non-selective beta blocker

    Decreases aqueous humour production via beta-adrenoreceptor blockade in the ciliary body

    Used in the management of glaucoma

    Can be used in combination with CAIs (may be more effective than either drug alone)

    Miosis, therefore do not use with uveitis and anterior lens luxation

    Systemic absorption ma occur from topical use resulting in bradycardia and lower BP

    Avoid in uncontrolled heart failure and asthma

    Can cause local irritation

    • Dogs q8-12h
    • Cats q12h
  30. Travoprost
    Travatan 0.004% solution

    Agonist for prostaglandin F receptors

    Reduces IOP by increasing uveoscleral outflow

    May have a profound effect on IOP

    Used in the management of primary glaucoma

    Can be used in acute conditions

    No published data for use in cats

    Often used in combination with CAIs

    • Comparable activity to latanoprost
    • Contraindicated in uveitis and anterior lens luxation due to marked miosis

    Conjunctival hyperaemia and mild irritation may develop

    (Increased iridal pigmentation seen in humans- not in dogs)

    1 drop per eye in evenings
  31. Cyclopentolate
    Cyclopentolate hydrochloride, Mydrilate

    Inhibits acetylcholine in the iris sphincter and ciliary body muscles

    Causes mydriasis and cycloplegia

    Mainly used pre-operatively for intraocular surgery

    Prolonged action 60 hours

    Rarely used in veterinary medicine

    Contraindicated in glaucoma and lens luxation

    May cause salivation in cats and chemosis in dogs
  32. Phenylepherine
    Ophthalmic 2.5% solution, Injectable 1% solution

    Alpha-1 selective adrenergic agonist

    Directly stimulates alpha-adrenergic receptors in the iris dilator musculature

    Causes vasoconstriction and mydriasis (not cycloplegic)

    Can be used to differentiate superficial conjunctival vessels from deeper episcleral vessels

    Used to diagnose Horners syndrome

    Slow onset for mydriasis - 2hours
  33. Tropicamide
    Tropicamide, Mydriacyl 0.5% or 1%

    Inhibits acetylcholine at the iris sphincter and ciliary body muscles

    Causes mydriasis and cycloplegia

    More potent mydriatic than cycloplegic and therefore less effective than atropine in relieving ciliary body muscle spasm

    Synthetic

    Rapid onset 20-30min

    Short duration 4-12h

    Avoid in glaucoma and use carefully in lens luxation

    May cause salivation in cats (less than atropine)
  34. Diclofenac
    Voltarol Ophtha 0.1% solution

    NSAID COX inhibitor that produces local anti-inflammatory effects



    Used to control pain and inflammation

    Used in cataract surgery to prevent intraoperative miosis

    Used to tx axonal miosis caused by ulcerative keratitis

    Can often be used when corticosteroids are contrindicated

    Can delay epithelial healing in ulcerative keratitis

    Has been associated with an increased risk of keratomalacia in humans (not reported in vet med)

    Potentially can increase IOP

    As with other NSAIDs it may cause local irritation

    q30min for 2hours pre-cataract op.
  35. Flubiprofen
    Ocufen 0.3% solution

    Inhibits prostaglandin synthesis

    NSAID COX inhibitor that produces local anti-inflammatory effects



    Used to control pain and inflammation

    Used in cataract surgery to prevent intraoperative miosis

    Used to tx axonal miosis caused by ulcerative keratitis

    Can often be used when corticosteroids are contrindicated

    Can delay epithelial healing in ulcerative keratitis

    Has been associated with an increased risk of keratomalacia in humans (not reported in vet med)

    Potentially can increase IOP

    As with other NSAIDs it may cause local irritation

    q 6-12h
  36. Ketorolac
    Acular 0.5%

    NSAID COX inhibitor that produces local anti-inflammatory effects



    Used to control pain and inflammation

    Used in cataract surgery to prevent intraoperative miosis

    Used to tx axonal miosis caused by ulcerative keratitis

    Can often be used when corticosteroids are contrindicated

    Can delay epithelial healing in ulcerative keratitis

    Has been associated with an increased risk of keratomalacia in humans (not reported in vet med)

    Potentially can increase IOP

    As with other NSAIDs it may cause local irritation

    q 6-24h
  37. Carbomer 980
    Viscotears, Lubrithal 0.2% gel

    Mucomimetic

    Replaces both aqueous and mucn components of the tear film

    Longer corneal contact time than aqueous tear substitutes

    Used in the management of KCS

    q4-6h
  38. Hyaluronate
    Vislube 0.18% solution

    Viscoelastic fluid (Sodium hyaluronate available in different formulations for intraocular surgery)

    Mucomimetic properties

    Longer corneal contact time than aqueous tear substitutes

    Used in the management of KCS

    q4-6h
  39. Hypromellose
    Hypromellose, Isopto, Tears Naturale. 0.3%,0.5%, 1% solutions

    Lacromimetic

    Cellulose based tear substitute

    Improves ocular surface lubrication

    Used in KCS

    Can be used as a vehicle v=base for compounding other drugs

    q1h
  40. Polyvinyl alcohol
    Liquifilm Tears, Sno Tears 1.4%

    Lacromimetic

    Synthetic resin tear substitute

    Used to lubricate eyes in KCS

    More adherent and less viscous than hypromellose

    q1h
  41. Proxymetacaine
    0.5% solution

    Local anaesthetic action

    Reversible blockade of Na+ channel, preventing propagation of the action potential along the nerve fibre

    Sensory nerve fibres are blocked before motor nerve fibres

    Rapid action 10 seconds

    Lasts for 20-55min depending on species

    Serial application increases duration and depth of anaesthesia

    Block reflex tear production and therefore STT1 should be performed before application

    Store in the refrigerator

    Conjunctival hyperaemia common

    Toxic to corneal epithelium and will delay ulcer healing
  42. Tetracaine
    0.5%, 1% solution

    Local anaesthetic action

    Proxymetacaine is used in preference to tetracaine

    Reversible blockade of Na+ channel, preventing propagation of the action potential along the nerve fibre

    Sensory nerve fibres are blocked before motor nerve fibres

    Serial application increases duration and depth of anaesthesia

    Block reflex tear production and therefore STT1 should be performed before application

    Store in the refrigerator

    Often causes marked conjunctival irritation, chemosis and pain on application.

    Toxic to corneal epithelium and will delay ulcer healing
  43. Tacrolimus (FK 506)
    Protopic 0.03%, 0.1% creams

    T lymphocyte inhibition

    Used in cases of KCS than are non responsive to ciclosporin

    Long-term effects and adverse effects are unknown

    Wear gloves when handling

    q12h

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