Wk 15 - Beta Adrenergic Antagonists

Question 1

Beta Blocker MOA

Answer 1

These are sympatholytic drugs, so they block B-2 receptors on the ciliary processes
Stimulation of those receptors by NE increases aqueous production, so blocking them decreases aqueous production
• IOP is reduced by ~25%

o How do alpha agonists, which are sympathomimetic, and beta blockers, which are sympatholytic, BOTH decrease aqueous production?
o Remember that alpha-2 receptors are pre-synaptic and stimulating them has an inhibitory effect so less NE is released
• There is less NE to stimulate the beta-2 receptors
o Beta-2 receptors are post-synaptic and they are stimulated by NE

Question 2

Beta Receptor Overview

Answer 2

Most ophthalmic beta blockers are nonselective, so they affect beta-1 and beta-2 receptors

Beta-1 receptors are located in the heart
o Beta blockers decrease cardiac contractility
- Always take pulse and BP before prescribing

Beta-2 receptors are located in the lung, liver, and eye
o Beta blockers inhibit bronchodilation
• Do not give to patients with COPD or asthma
o Beta blockers can mask symptoms of hypoglycemia
• Caution in diabetics?

Question 3

Beta Blocker Ocular Clinical Uses

Answer 3

• Treatment of POAG
• Prophylactic prevention of IOP elevation following laser trabeculoplasty, capsulotomy, or iridotomy
• Treatment of steroid IOP response
• Treatment of some secondary glaucomas

Question 4

Beta Blocker Effectiveness

Answer 4

Very effective blunting usual AM rise in IOP
o Usually dosed qmornings
o Not very effective overnight

10-20% of patients do not respond to beta blockers
o Determine drug’s effectiveness in a patient using monocular trial
o Use drug in one eye only, follow up in ~1 month to compare IOPs
o Not super scientific, but gets the job done
o There is some systemic crossover, so dosing in one eye only may still affect the other eye’s IOP slightly

Expect slightly less IOP reduction in patients already taking an oral beta blocker
o They were getting some reduction already from the systemic med

Question 5

Beta Blocker Dosing

Answer 5

Beta blockers were originally dose BID

Timolol XE gel and Istalol were developed to have increased contact time or better corneal penetration for qday dosing

New research shows that any formulation can be effective when dosed qday in the AM

Common practice
o Start patient on a PGA (first choice) or a beta blocker qday
o If moving from PGA qday therapy to BID
• Rx PGA PM and beta blocker AM

Question 6

Beta Blocker Side Effects

Answer 6

Ocular side effects
•	Mild stinging and burning
•	Redness
•	Rare allergy
•	Corneal hypoaesthesia

Systemic side effects
• Bradycardia and hypotension
-This is why you take baseline pulse and BP before prescribing
-May make young, active patients feel tired
• Fatigue
• Bronchospasm
• Nausea, alopecia, urticaria
• Depression, impotence, hypoglycemia??? - These side effects have been reported but have been challenged recently

Question 7

Beta Blocker Contraindications

Answer 7

• COPD or asthma
• Sinus bradycardia
• Congestive heart failure
• Myasthenia gravis
• Normal tension or congenital glaucoma
• Depression? Diabetes? - Despite recent challenges, you should still probably pick something else

Question 8

Timolol Maleate (Timoptic, Ocudose, Timoptic XE, Istalol)

Answer 8

Timoptic 0.25% and 0.5%
o Gold standard for IOP reduction
o Available in two concentrations
• Melton and Thomas suggest using 0.25% (blue cap) for fair-skinned patients and 0.5% (yellow cap) for darker-skinned patients
o Generic available
• Both generic and brand name are pretty inexpensive
• There can be inconsistency between generic brands
• Try switching to brand name if your patient has fluctuating IOP and you rule out compliance as the causative factor

Ocudose PF 0.25% and 0.5%
o Preservative-free, unit dose timoptic

Timoptic XE gel 0.5%
o Developed with qday dosing indication
o Gel increases contact time

Istalol 0.5%
o Contains potassium sorbate to increase lipophilicity and corneal penetration
o Also developed with qday dosing indication

Question 9

Timolol Hemihydrate 0.25% and 0.5% (Betimol)

Answer 9

• Brand name only
• Cheaper than timolol maleate
• Comparable efficacy to maleate

Question 10

Betaxolol 0.25% susp (Betoptic)

Answer 10

Beta-1 selective
o Less IOP lowering effect than timolol
o Fewer respiratory side effects
• WAS the best choice for asthma/COPD before PGAs, now you should pick a PGA over betaxolol for those patients

Possible better prevention of visual field loss than timolol
o Thought to be from calcium channel-blocking effects and reduced vasoconstriction in the eye
o May be a good choice to pair with a PGA

Dosing: BID when used as monotherapy

Question 11

Carteolol 1% (Ocupress)

Answer 11

Not widely used

Non-selective beta blocker, with intrinsic sympathomimetic activity
• Less effective than timolol

Crosses blood-brain barrier less than timolol
o Reduced depression?

Less negative effect on cholesterol

Question 12

Cosopt (dorzolamide/timolol maleate)

Answer 12

•	Beta blocker + CAI
•	Reduces IOP 27%
•	Dosing: BID
o	As effective as dosing the two meds separately, with better compliance
•	Cosopt PF
o	Preservative free, unit dose

Question 13

Combigan (0.2% brimonidine/0.5% timolol)

Answer 13

Beta blocker + alpha agonist
o Uses original 0.2% Alphagan concentration before it was reduced to 0.1%

Dosing: BID
o Slightly less effective than dosing the two meds separately, but better compliance

Fewer allergy issues than Alphagan
o Possibly due to vasoconstriction caused by timolol?