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Nervous System: Unit III > Ocular Pharmacology > Flashcards

Flashcards in Ocular Pharmacology Deck (18)
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1

Pharmacokinetics of topical ocular administration

  • primary systemic absorption via nasolacrimal drainage
    • nasal mucosa avoids first-pass metabolims ==> systemic side-effects
  • secondary systemic absorption via corneal absorption ==> aqueous humour and trabecular pathway
    • drugs must remain @ front of the eyeto be absorbed through the cornea
  • drugs can be prepared as suspensions or gels for prolonged action

2

Factors impacting rate/extent of absorption into ocular structures

  • time drug remains in cul-de-sac and precorneal tear film
  • elimination by nasolacrimal drainage
  • drug binding to tear proteins
  • drug metabolism by tear and tissue enzymes
  • diffusion across cornea and conjunctiva

3

Anatomical drug targets @ eye

  • iris
  • cornea
  • ciliary body = location of aqueous humour production
  • canal of schlemm
  • trabecular meshwork

4

General characteristics of glaucoma

  • increase in intraocular pressure
  • must decrease IOP via decrease production of aqueous humor and increase outflow.
  • Normal = 10-15, >20 is bad.
  • Types:
    • narrow angle
    • open angle 
    • closed angle

5

Tx strategies for narrow angle glaucoma

  • avoid dilation ==>
  • no α-1 agonists
  • no muscarinic antagonists.

6

Risk factors/characteristics/tx strategy for open angle glaucoma

  • ciliary body β2 stimulation causes increase in aqueous humour production -
  • Risk factors: increased IOP - prophylactic reduction of IOP reduces incidence of glaucoma
    • ↑ IOP
    • + family history
    • African american
    • possibly myopia
  • Leading/most preventable cause of blindness
  • Treatment: go after outflow in this case, reduce IOP
    • Give tropical drops

7

Pathophysiology/tx strategy for closed angle glaucoma

  • Pathophysiology = mechanical blockage of the trabecular meshwork by the peripheral iris.
    • Blockage occurs intermittently and results in extreme fluctuations in IOP that may need to be treated as an emergency to avoid visual loss.
  • Emergent eye problem
  • Initial treatment is rapid reduction of IOP- pilocarpine
  • Systemic medications are acetazolamide and mannitol
  • Definitive treatment
    • Laser peripheral iridotomy
    • Avoid decongestants and anticholinergic agents while awaiting surgery

8

Latanoprost: MOA, role in glaucoma

  • MOA
    • prostaglandin analog 
    • Increases uveoscleral outflow
  • Role in glaucoma
    • First-line/initial treatment of open angle glaucoma
    • Increase outflow

9

Latanoprost (Xalatana): Use-limiting SE/contraindication

  • Brown discoloration of iris
  • Eyelash lengthening
  • Ocular irritation
  • Few systemic effects

 

10

Pilocarpine (Ocursert): MOA; role in glaucoma

  • MOA = cholinergic agonist
  • Role
    • Less commonly used today
    • Emergently decrease IOP in closed angle glaucoma

11

Pilocarpine (Ocusert): use-limiting SE/contraindication

  • Ciliary spasm ⇒ HA,
  • Myopia
  • Dim Vision

12

Brimonidine (Alphagan): MOA; role in glaucoma

  • MOA
    • α2 adrenergic agonist ⇒ ↓  production, ↑ outflow
    • α2 is coupled to Gi ==> less aqueous humor
    • increases uveoscleral outflow
  • Role
  • 2nd line along with β  blockers and CAI’s in open angle glaucoma

 

13

Brimonidine (Alphagan): use-limiting SE/contraindication

  • Red eye and ocular irritation
  • Neonates: CNS depression, hypotension, somnolence and apnea

 

14

Timolol (Timoptic): MOA; role in glaucoma

  • MOA
    • β adrenergic antagonist ⇒ ↓  production of aqueous humor
    • Can also decrease ocular blood flow, which decreases ultrafiltration required for production
  • Role
    • 2nd line treatment in open angle glaucoma if IOP still not in target range

15

Timolol (Timoptic): use-limiting SE/contraindication

  • Depression, fatigue, bradycardia, respiraory depression
  • AVOID in patients with asthma, bradycardia, COPD

16

Dorzolamide (Trusopt): MOA; role in glaucoma

  • MOA
    • carbonic anhydrase inhibitor ⇒ ↓  production
  • Role
    • 2nd/3rd line treatment If not tolerant to β-blocker in open angle glaucoma

17

Dorzolamide (Trusopt): use-limiting SE/contraindication

  • Topical administration greatly decreases systemic effects:
    • fatigue
    • depression
    • paresthesias
    • renal stones

18