2.5 - Drugs for Glaucoma Flashcards
Which structure produces aqueous humour? Where does it secrete it into?
The ciliary body secretes aqueous humor into the posterior chamber of the eye
What are the two paths of outflow of aqueous humor?
Main outflow:
Trabecular/conventional - circulates iris, and flows out of pupil into anterior chamber
Nonconventional
uveoscleral - leaves the anterior chamber by diffusing through intercellular spaces among ciliary muscle fibers.
Healthy intraocular pressure (IOP) is a result of what?
The equilibrium between aqueous humor production and outflow (or absorption)
If aqueous humor outflow from the anterior chamber is impeded, what will happen?
Back pressure will develop, and intraocular pressure (IOP) will rise.
What is glaucoma?
Visual field loss secondary to optic nerve damage caused by increased intraocular pressure (IOP).
–> 2nd leading cause of blindness in older North Americans
What are the two kinds of glaucoma?
Primary open angle glaucoma (POAG)
–> Increased resistance to outflow through trabecular meshwork
Angle-Closure Glaucoma
–> A closed angle between the iris and lens obstructs trabecular outflow pathway (medical emergency)
What are the risk factors for primary open-angle glaucoma (POAG)?
Increased age, being of African descent, high IOP, family history
How can drugs reduce IOP?
Improve aqueous humor outflow OR reduce aqueous humor production
What are the first line monotherapy drugs for primary open angle glaucoma?
Prostaglandin F2alpha analogs
What are some second line adjunctive therapy for primary open angle glaucoma?
–> Beta blockers
–> Alpha 2 agonists
–> Carbonic anhydrase inhibitors
–> PSNS agents (Cholinergic agonists)
What percent of topical glaucoma medications might reach systemic circulation and cause adverse effects?
~10%
What kind of drugs are latanoprost, travoprost, and bimatoprost?
Prostaglandin F2alpha analogs
How do prostaglandins F2alpha analogs such as latanoprost, travoprost, and bimatoprost work?
They lower IOP in glaucoma or ocular HTN by facilitating aqueous humor outflow (mostly uveoscleral outflow)
How do beta blockers and prostaglandin F2alpha analogs compare for glaucoma treatment?
the analogs are just as effective as beta blockers, with fewer adverse effects.
What are the adverse effects of prostaglandin F2alpha analogs?
–> Darkening of pigmentation of iris and eyelid
–> Thickening/lengthening of the eyelashes
What beta blockers are used to treat glaucoma?
Timolol & levobunolol (non-selective)
Betaxolol (B1 selective)
Why do beta blockers help with glaucoma?
Lowers IOP by decreasing production of aqueous humor in the ciliary body (mostly through B2 antagonism)
What are some systemic adverse effects to beta blockers for glaucoma?
Same as other beta blockers
What kinds of drugs are brimonidine and apraclonidine?
A2 agonists used to treat glaucoma
How do A2 agonists like brimonidine and apraclonidine treat glaucoma?
Lowers IOP by reducing ocular vasoconstriction, which reduces aqueous humor production in the ciliary body (and may improve aqueous humor outflow)
What are the adverse effects of A2 agonists that treat glaucoma, such as brimonidine and apraclonidine?
–> Lowers blood pressure
–> Dizziness
–> Decreased HR
–> Lethargy
–> Fatigue + drowsiness
–> Dry mouth/nose
–> Anxiety
–> Sleep disturbances
What kinds of drugs are brinzolamide and dorzolamide?
Carbonic anhydrase inhibitor
How do carbonic anhydrase inhibitors such as brinzolamide and dorzolamide work to treat glaucoma?
Inhibits enzyme carbonic anhydrase that facilitates this reaction necessary to aqueous humor production:
CO2 + H2O –> HCO3- + H+
Therefore, reduces IOP by decreasing production of aqueous humor in ciliary body
What are some adverse effects of carbonic anhydrase inhibitors used to treat glaucoma, such as brinzolamide, dorzolamide?
–> Ocular stinging
–> Bitter taste
–> Allergic reaction in 10-15% of pts
How does angle-closure glaucoma present?
Usually unilateral
–> Red eye, hazy cornea, dilated pupil, dull pain
What are some risk factors for angle closure glaucoma?
–> Age
–> Female
–> Being of east Asian or Inuit descent
How would you treat angle-closure glaucoma?
With a cholinergic agonist (Pilocarpine or carbachol), or indirectly through an AChE inhibitor (echothiophate)
Why might a cholinergic agonist work to treat angle-closure glaucoma?
Contraction of the ciliary muscle improves trabecular outflow (but focuses the lens for accommodation)
What are some side effects for parasympathomimetics (such as pilocarpine or echothiophate) used for glaucoma?
–> excessive PSNS effects
–> Possible cataracts with long-term sue
