Pharmacology Flashcards
What is required from topical drugs applied to the eye?
they need to act on the surface
they need to penetrate the cornea
What type of drugs are good for corneal penetration?
LMW drugs
How many layers are there in the cornea and what are they?
5 layers epithelium Bowman's layer (membrane) Stroma Descent's membrane Endothelium
what is the epithelium in terms of hydro/lipo philic/phobic?
lipophilic
hydrophobic
what is the stroma? in terms of hydro/lipo philic/phobic?
hydrophilic
lipophobic
which layer do lipid soluble drugs penetrate?
the epithelium
which layer do water soluble drugs penetrate?
the stroma
what type of drugs penetrate the cornea easily?
drugs that have both lipophilic and hydrophilic properties
Give an example of a drug that has both lipophilic and hydrophilic properties and penetrates the cornea easily?
chloramphenicol
what can reduced the hydrophobic nature of the epithelium?
ocular surface inflammation
which layer of the tear film may impede drug penetration
the lipid layer
which layer of the cornea limits hydrophilic drugs?
epithelium
which layer of the cornea limits hydrophobic drugs?
stroma
what properties must topical steroids (for the eye) have?
hydrophobic and hydrophilic capability
What is the affect of the addition of alcohol or acetate to a topical steroid?
makes it more hydrophobic
what is the affect of the addition of phosphate to a topical steroid?
makes it more hydrophilic
is prednisolone acetate hydrophilic or hydrophobic?
hydrophobic
does prednisolone acetate have good penetration an uninflamed cornea?
yes
When is prednisolone acetate used?
post-operatively
Is prednisolone phosphate hydrophilic or hydrophobic?
Hydrophilic
Does prednisilone phosphate have good penetration of the uninflamed cornea?
no
when is prednisolone acetate used?
Used for cornea disease or when want low dose steroids
What preservative can be added to a drug to enhance corneal penetration?
How does it work?
Benzalkonium
disrupts the lipid layer of the tear film
What drug is used to lower IOP in glaucoma?
Bimatoprost 0.03%
where can drugs applied topically at the eye be systemically absorbed?
at the nasopharynx
What are other routs of administration of drugs a the eye? (not topical)
subconjunctival
subtenons
What are the 2 types of ocular injections?
intravitreal
intracameral
What are some anti-inflammatory agents?
steroids
topical NSAIDs
Anti-histamines
mast cell stabilisers
What is the action of steroids?
suppress inflammation, allergy and immune responses
In what eye conditions are topical steroids indicated?
post op cataracts
uveitis
to prevent corneal graft rejections
What are some local side effects of topical steroids in the eye?
cataract
glaucoma
exacerbation of viral infection
What are some systemic side effects of steroids?
Gastric ulceration Immunosuppression Osteoporosis Weight gain Diabetes Neuropsychiatric effects
What are the different strengths of topical steroids?
FML
Predsol
Betamathasone
Dexamethasone/ prednisolone
When would anti-histamines and mast cell stabilisers be used?
in hay fever / allergic conjunctivitis
When would NSAIDs be used?
pain relief post refractive laser
What is the only modifiable risk factor in glaucoma?
raised intra-ocular pressure
What drugs are used to treat glaucoma?
Prostanoids - latanoprost (xalatan) beta blockers (timolol) carbonic anhydrase inhibitors Alpha2 adrenergic agonist Parasympathomimetic
What is the mechanism of action of prostanoids?
increase aqueous outflow
What is the mechanism of action of beta blockers?
reduce aqueous production
When are beta-blocker contraindicated?
COPD / ashma / heart block
what is the name of a commonly used topical Carbonic anhydrase inhibitor
Dorzolamide - trusopt
what is the name of a commonly used oral Carbonic anhydrase inhibitor
acetazolamide - diamox
what is the action of Parasympathomimetic drugs and give an example
pilocarpine
improve aqueous outflow and constrict pupil
what is the advantage of Intravitreal drug administration?
Delivers effective concentration of drug at target site instantly
What is the problem with Intravitreal drug administration
many drugs are toxic to the retina
When is Intravitreal drug administration used?
antibiotics in endophthalmitis
Used to deliver intra-ocular steroids
Anti-VEGF
How does topical anaesthetic applied to the eye work?
Blocks sodium channels and impedes nerve conduction
When is local anaesthetic used in ophthalmology?
1) FB removal
2) Tonometry (IOP measurement)
3) corneal scraping
4) comfort
What is the most comply used diagnostic dye?
fluorescein
What is fluorescein used for?
shows corneal abrasions
tonometry
diagnosing nasolacrimal duct obstruction
angiography
What are some examples of mydriatics?
tropic amide
cyclopentolate
what is the effect of mydriatics and how do they work?
cause pupil dilation by blocking parasympathetic supply to iris
What are the side effects of mydriatic drugs?
blurring
AACG
What are some examples of Sympathomimetics and what do they do?
phenylephrine, atropine
Acts on sympathetic system
Causes pupil to dilate
what drug is comply associated with Optic Neuropathy
Ethambutol - The TB drugs
What drug is associated with maculopathy?
Maculopathy - treats malaria
