Exam 3 Pharm Material: Ocular Hypotensive Drugs/Ocular Hyperosmotic Drugs Flashcards
What is the general path of aqueous production and outflow?
Aqueous is produced by the ciliary epithelium and is secreted into the posterior chamber. The aqueous flows through the pupil into the anterior chamber and follows the convection current towards the trabecular meshwork. The trabecular meshwork accounts for 80-90% of outflow through the conventional pathway that travels through the TM into Schlemm’s canal and then to the episcleral venous plexus. The other 10-20% of aqueous outflow occurs through uveoscleral outflow.
How does the autonomic system impact aqueous production and outflow?
Production: Sympathetic innervation of the CB alpha receptors decreases production. Innervation of beta receptors on the CB increases production.
Outflow: Parasympathetic innervation of M3 receptors on the iris sphincter and causes contraction. This contraction will cause miosis and stretch the TM, increasing outflow. Parasympathetic innervation of M2 receptors of the longitudinal muscle of the CB causes contraction. This contraction will pull on the scleral spur, increasing outflow.
Production: Sympathetic ONLY
Outflow: Parasympathetic ONLY
What are the different hypotensive drug classes? What are their cap colors?
Cholinergic Agonists/Miotics: Dark Green Beta-Blockers: Yellow: 0.5% Light Blue: 0.25% Alpha Adrenergic Agonists: Purple Prostaglandin Analogs: Turquoise Carbonic Anhydrase Inhibitors: Orange Rho-Kinase Inhibitors: White?
What is the MOA of cholinergic agonists?
Bind to the M3 receptors of the iris sphincter muscle causing miosis. Miosis will stretch the TM increasing outflow.
What are the direct-acting cholinergic agonists? What does direct-acting mean?
Isopto carpine/Pilocarpine
Pilopine HS/Pilocarpine HCL (gel)
Direct-acting means they act on the receptors themselves and stimulate the receptor.
What are cholinergic agonists particularly useful for?
Narrow/closed-angle glaucoma. Miosis pulls the peripheral iris away from the angle increasing outflow.
What are some side effects of cholinergic agonists?
Headache, blurred vision, narrowing angle, retinal detachment
Blurred vision can occur due to less light being let in due to miotic pupil.
Angle narrowing can occur because as the ciliary body muscles contracts the iris is pushed forward and causes angle-closure.
Retinal detachment can occur due to increased tension on the peripheral retina due to the ciliary body contraction
What is the indirect cholinergic agonist? What is the side effect that is unique to this drug?
Phospholine Iodide/Echothiophate. It is clinically indicated for accommodative esotropia.
Echothiophate can cause the same side effects as pilocarpine/pilocarpine HCL but it also can cause iris cysts. These cysts can cause a pupillary block.
When does maximum IOP decrease occur with cholinergic agonists?
2 hours
What is the MOA of a beta-blocker?
Blocks beta 2 receptors and beta 1 receptors reducing aqueous production.
(Betoptic/Betaxelol is selective for beta 1 receptors, this makes betaxolol cardioselective)
What are the true contraindications of the nonselective beta-blockers? (3)
Atrioventricular Block
Sinus bradycardia
Obstructive pulmonary disease
What phenomenon are beta-blockers known for?
Short term escape and long term drift
Short term escape: Sudden sharp increase in IOP after several weeks of treatment.
Long term drift: Receptor tolerance develops after months or years of use.
When do beta-blockers have little to no effect?
At night, usually dosed in the morning
What are the different beta-blockers? (7)
Betagan/Levobunolol hydrochloride
Betimol/timolol hemihydrate
Betoptic-S/betaxolol hydrochloride (Beta-1 Selective)
Istalol/Timolol maleate
Optipranolol/metipranolol (not used often)
Timoptic/Timolol maleate
Timoptic XE/Timolol maleate gel-forming solution
How much do beta-blockers reduce IOP by (%)?
20-30% reduction
Only 15-20% with Betoptic-S
How much do cholinergic agonists reduce IOP by (%)?
Echothiophate & Pilocarpine: 15-25%
Pilocarpine HCL: 20-30%
What are the common dosages for beta-blockers?
QD-BID, but most effective if QD in morning
What are the common dosages for cholinergic agonists?
QD-BID for echothiophate
BID-QID for pilocarpine
What is the MOA of Carbonic Anhydrase Inhibitors?
Inhibit carbonic anhydrase in the ciliary processes to decrease bicarbonate. This decreases sodium and fluid movement decreasing aqueous production.
What are the different CAI’s?
Brinzolamide/Azopt
Dorzolamide/Trusopt
Aetazolamide/Diamox
Methazolamide/Naptazane
What are the side effects of beta-blockers? (5)
Bronchospasm Hypotension Bradycardia Depression Lethargy
What are contraindications for TOPICAL CAI use?
Sulfa allergy Compromised cornea (Fuch's/Transplant)
What are the contraindications for ORAL CAI use?
Liver disease
Pregnancy
Kidney disease (or stones)
Sulfa Allergy
What specific isoenzyme do CAI’s inhibit?
Isoenzyme CA-II
What is the dosage of a CAI if used as monotherapy? What is the dosage of a CAI if used in adjunct with a BB or PGA?
Monotherapy: TID
Adjunct: BID
Which topical CAI will be more likely to cause blurred vision? Which topical CAI will be more likely to sting upon instillation?
Blurred Vision: Azopt/Brinzolamide (Suspension)
Stinging: Trusopt/Dorzolamide (5.6 pH)
What are oral CAI’s used for?
Fast IOP reduction. Examples include acute angle closure or pupillary block glaucoma.
What is the adverse effect of oral CAI’s? (Not contraindications)
Transient myopia
What is the MOA of alpha 2 adrenergic agonists?
Bind to alpha 2 receptors on the ciliary body, decreasing Na/K+ ATPase and reducing aqueous humor production.
Brimonidine also increases uveoscleral outflow but NOT apraclonidine.
What are the different alpha 2 adrenergic agonists?
Alphagan P/Brimonidine
Iopidine/Apraclonidine
By how much do CAI’s reduce IOP (%)?
15-20%
By how much do alpha 2 adrenergic agonists reduce IOP (%)?
Up to 25-26% (Brimonidine 26%, Apraclonidine 25%)
What are the side effects of alpha 2 adrenergic agonists?
Dry mouth
Follicular conjunctivitis (patients may report increased discomfort when putting drops in as time goes on)
Mydriasis
ALLERGY (Apraclonidine > Brimonidine)
What are the contraindications for using alpha 2 adrenergic agonists to treat glaucoma?
- Children under 6 or weighing less than 20kg (increased systemic the side effects like lethargy, hypotension, bradycardia, etc)
- Patients using monoamine oxidase inhibitors for depression
- Patients with severe cardiac disease
What are some precautions when prescribing alpha 2 adrenergic agonists for glaucoma treatment?
Concurrent depression
Reynaud phenomenon
Orthostatic hypotension