Ophthalmic drugs Flashcards
for a subconjunctival injection what volume of drug is usually injected and what gauge needle is used?
0.2-0.5ml with 25-27 gauge needle
what are the 2 possible routes of movement for drugs through the corneal epithelium?
transcellular and paracellular
what route do lipophilic drugs take through the corneal epithelium?
transcellular
what route do hydrophilic drugs take through the corneal epithelium?
paracellular
what are the 3 possible routes for a drug after permeation of the conjunctiva?
laterally movement into the corneal stroma
posteriorly across the sclera
absorbed into systemic circulation
is the sclera more or less permeable than the cornea and why? It is more permeable to hydrophilic or lipophilic molecules?
10 x more permeable because it has no epithelium
more permeable to hydrophilic molecules
name 3 substances used to modify osmolarity of a drug
sodium chloride, boric acid, dextrose
what pH is generally well tolerated for topical ocular drugs?
4.5-9
give 2 ways to improve the corneal penetration of a drug
prodrugs (more lipophilic prodrug crosses epithelium and transforms into active drug egg, red acetate, latanoprost/travoprost) penetration enhancers (EDTA, benzalkonium chloride)
are penicillins bactericidal or bacteristatic? what is there MOA?
bactericidal,
inhibit bacterial cell wall synthesis
name a first generation cephalosporin and a second generation cephalosporin
first: cephalexin
second: cefuroxime
name 5 antibiotic groups that affect bacterial protein synethesis
ahminoglycosides, tetracyclines, macrolides, lincosamides, chloramphenicol
name 2 amino glycoside antibiotics
2 from:
neomycin, gentamicin, tobramycin, kanamycin and amikacin
true or false: ahminoglycosides have poor gram negative activity and are mainly affected against staph aureus
false:
They have excellent gram-negative activity although neomycin is generally inactive against Pseudomonas aeruginosa. Their gram-positive activity is limited primarily to Staphylococcus aureus and they are inactive against anaerobes
are tetracyclines bactericidal or bacteriostatic?
bacteriostatic
give an example of a macrolide antibiotic
one from:
erythromycin, azithromycin and clarithromycin
what’s the more frequently used lincosamide antibiotic?
clindamycin
is chloramphenicol bactericidal or bacteriostatic?
bacteriostatic
true or false: chloramphenicol is useful for prophylaxis following intraocular surgery?
true:
owing to excellent corneal penetration (due to high lipophilicity of the drug)
give 2 examples of antibiotic groups that alter folic acid synthesis. Are they bactericidal or bacteriostatic?
sulphonamides and trimethoprim
both bacteriostatic
what is a possible risk of using TMS?
side effects of KCS
what is the MOA for fluoroquinolone? are they bacteriostatic or bactericidal?
inhibit bacterial DNA synthesis
bactericidal
true or false: enrofloxacin has good gram negative and gram positive activity
truew
what generation fluoroquinolone is ofloxacin?
second
what are the 3 anti-fungal classes most relevant to veterinary ophthalmology?
polyenes, pyrimidines, azoles
how what is the MOA for polyenes? are they fungicidal or fungistatic?
bind to ergosterol in the fungal cell membrane causing leakage of cell contents
fungicidal at high concentrations
give 2 examples of polyene anti fungals
two from
amphotericin B, natamycin and nystatin
are pyrimidines fungicidal or fungistatic?
fungistatic
what is the MOA of azoles? and what classes are they divided into?
inhibit ergosterol synthesis.
imidazole and triazoles
is ketoconazole a imidazole or triazole?
imidazole
give 3 examples of triazoles
fluconazole, itraconazole, voriconazole
In the absence of an authorised product for a specific indication in the dog in the UK, which of the following products should you consider prescribing first under the Cascade?
a. A veterinary medicinal product authorised for use in the dog but for a different indication
b. A medicinal product authorised for the same indication in man
c. A veterinary medicinal product authorised for use in another country
d. A medicinal product prepared extemporaneously by a pharmacist
a. A veterinary medicinal product authorised for use in the dog but for a different indication
Which of the following statements regarding the topical ophthalmic application of drugs is TRUE?
Select one:
a. Solutions tend to have longer corneal retention times than ointments
b. The systemic route is usually preferred for treatment of ocular surface disease
c. Topically applied drugs usually achieve therapeutic concentrations in the posterior segment of the eye
d. In order to penetrate the intact cornea the agent must have lipophilic and hydrophilic properties
d. In order to penetrate the intact cornea the agent must have lipophilic and hydrophilic properties
Which of the following antibacterial agents is bacteriostatic? Select one: a. Cephalexin b. Gentamycin c. Chloramphenicol d. Bacitracin
c. Chloramphenicol
Put the following in decreasing order of in vitro efficacy against FHV-1 are:
Select one:
Acyclovir, ganciclovir, trifluorothymidine, cidofovir
Trifluorothymidine > ganciclovir > cidofovir > acyclovir
Which of the following topical ophthalmic corticosteroids is the most potent? Select one: a. Prednisolone acetate 1% b. Betamethasone sodium phosphate 0.1% c. Prednisolone sodium phosphate 0.1% d. Fluoromethalone 0.1%
a. Prednisolone acetate 1%
Which of the following antibacterial agents is commonly used as prophylaxis against ocular surface infection in dogs? Select one: a. Polymyxin B b. Gentamycin c. Chloramphenicol d. Doxycycline
c. Chloramphenicol
The main ocular side effect associated with topical ophthalmic use of corticosteroids in dogs is Select one: a. Corneal oedema b. Ocular hypertension c. Cataract formation d. Lipid keratopathy
d. Lipid keratopathy
Which of the following statements regarding ciclosporin is FALSE?
Select one:
a. Ciclosporin improves clinical signs in KCS through suppression of immune-mediated destruction of lacrimal tissue
b. Ciclosporin has excellent corneal penetration when applied topically, and thus may be used to treat intraocular immune-mediated disease
c. Ciclosporin is authorised for the treatment of canine KCS and chronic superficial keratitis as a 0.2% eye ointment
d. Ciclosporin is a calcineurin inhibit
b. Ciclosporin has excellent corneal penetration when applied topically, and thus may be used to treat intraocular immune-mediated disease
Which of the following statements regarding mydriatic agents is TRUE?
Select one:
a. Mydriatics which do not induce cycloplegia are usually associated with an increase in IOP
b. Mydriasis is achieved by blockade of sympathetic-mediated iris muscle activity
c. Epinephrine has good corneal penetration and can be used topically to induce mydriasis
d. Mydriatics should be used in caution in patients with lens instability
d. Mydriatics should be used in caution in patients with lens instability
Place these ocular hypotensive agents in the appropriate drug group Timolol Latanoprost Mannitol Dorzolamide Brinzolamide
Timolol - b blocker
Latanoprost - PG analogue
Mannitol - hyper osmotic agent
Dorzolamide and brinzolamide - carbonic anhydrase inhibitors
true or false: only mydriatics which block the parasympathetic system can effect cycloplegia
true
Name two parasiticides licensed for treatment of lungworm (Angiostrongylus vasorum) infection in dogs
two from:
fenbendazole
moxidectin
milbemycin praziquantel
Does topical ciclosporin have good or bad corneal penetration? Why?
bad - it is lipophilic
What is the normal rate of tear film turnover?
1ul/min
Which enzyme is responsible for the degradation of cell membranes to release arachidonic acid?
phospholipase 2
What are the ocular effects of prostaglandin release within the anterior segment of the eye?
disruption of BAB miosis cell and protein exudation conjunctival hyperaemia hypotony
Which factors influence bioavailability of topically applied corticosteroids?
- Antiinflammatory potency of the base steroid
- Concentration of the base steroid in the formulation
- Type of formulation (solution, suspension or ointment)
- Solubility characteristics of the base steroid
- Patient factors (e.g. presence/absence of intact corneal epithelium)
Arrange these corticosteroids in order of increasing potency: prednisolone, dexamethasone, hydrocortisone, triamcinolone
hydrocortisone < prednisolone < triamcinolone < dexamethasone
Which has better corneal penetration – 1% prednisolone phosphate or 1% prednisolone acetate? Why?
acetate
more lipophilic
Give two examples of direct-acting cholinergic agonists which may be used as ocular hypotensive agents.
pilocarpine
carbachol
What are the postulated mechanisms of action of topical beta blockers in reducing IOP?
- Blockade of the β-receptors of the ciliary body epithelium results in reduced activation of adenylate cyclase which leads to a reduction in cAMP formation and ultimately in AH formation
- Inhibition of Na+/K+-ATPase activity leading to a reduction in AH formation
- They may exert a vasoactive effect and increase AH outflow
Which layer(s) does(do) carbomer 980 (polyacrylic acid) mimic?
aqueous and mucin
Name 2 ophthalmic uses of mitomycin C
to suppress formation of fibrous tissue around glaucoma implant devices
to reduce corneal scarring when used in eye drop formulation.
What is the duration of mydriasis caused by topical 1%
tropicamide in the dog?
6-12 hours
What is the duration range of mydriasis caused by topical 1% atropine in the normal canine eye?
96-120 hours
what is the average volume of an eye drop?
50ul
give 3 disadvantages of ointments
Toxic to anterior segment (contraindicated in corneal and scleral perforations)
Blurring of vision
more difficult to apply and achieve accurate dosing
give 4 disadvantages of solutions/suspensions
Short contact time necessitates frequent application
Drainage via nasolacrimal appaats is signiant it potential for systemic absorption
Quickly diluted in irritated eyes by excess tear production
Negligible lubricant effect
give 2 examples of collagenases
matrix metalloproteinases
serine protease
name 3 types of cell that can release collagenases
neutrophils
bacteria (esp pseudomonas and b haemolytic strep)
keratocytes
name 2 anti-collagenases found in serum
alpha2-macroglobulin
alpha2-antitrypsin
what 3 components of serum help with epithelial growth, migration and differentiation?
epithelial growth factor
platelet-derived growth factor
vitamin A
what dosage of TPA is associated with intraocular toxicity in the dog and cat?
> 50ug
