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BHS 254.2
Notetaker: Melissa Milbrandt
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Date: 2/8/2016
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Phenylephrine continued
o No cycloplegia or blockade of active light reflex because there is no effect on muscarinic
receptors: need to add Tropicamide to get these effects
o Increased effect with LA due to better absorption
o Sympathetic tone varies in different people, is decreased in older people
o Decreased effect in dark irides
o Even 1/8% can rarely cause angle closure
o Counteracts miotics, can be used in 2.5% for examining open angle glaucoma patient on
miotics
o Horner’s syndrome
 Sympathetic denervation somewhere along the pathway from the CNS to the
eye, prevents information from CNS from getting to effector cells in the eye
 Three characteristic signs: ptosis, miosis, facial anhydrosis
 Phenylephrine will treat ptosis from Horner’s
 Diagnosis: effector cells are supersensitive to sympathetic stimulation –
adrenergic agonists cause exaggerated response
 Only accurate in 71% of eyes with Horner’s
o 10% dose after local anesthetic can be used to break posterior synechiae
o 2.5% can be used to treat miotic cysts from Acetylcholinesterase Inhibitor
o Toxicities
 Contraindications: thyrotoxicosis, coronary artery disease, hypertension
(especially with 10% solution, but still caution with 2.5%)
 Drug interactions: tricyclic antidepressants, MAO inhibitors, guanethidine,
reserpine
 These already enhance action of NE or adrenergic agonists on their own,
Phenylephrine will add to it
 Systemic effects
 CNS stimulation, headache
 CV effects: hypertension, subarachnoid hemorrhage, ventricular
arrhythmias, tachycardia, reflex bradycardia, blanching of the skin (due
to vasoconstriction)
 Local and ocular effects
 Transient pain
 Excessive lacrimation
 Keratitis
 Liberation of iris pigment (floaters, especially with older patients with
dark irides)
 Post-dilation miosis (especially in older patients)
 Rebound congestion (rebound hyperemia) due to conjunctival hypoxia
from vasoconstriction
 Angle closure
Apraclonidine (Iopidine) 0.5%, 1.0%
o Alpha agonist, some selective for alpha-2
BHS 254.2
Notetaker: Melissa Milbrandt
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Date: 2/8/2016
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Main mechanism: stimulates alpha-2 post-synaptic receptors, inhibits adenylate cyclase,
decrease cAMP, decrease aqueous humor production in ciliary body
Secondary mechanism: increase uveoscleral outflow, but not through remodeling
1% is approved for use with argon laser trabeculoplasty, argon laser iridotomy, and
Nd:YAG posterior capsulotomy to bring down increased IOP right after these procedures
o 0.5% can be used for long term use reduce IOP in primary open angle glaucoma (POAG)
 There is some alpha-1 stimulation, so cannot be used in patients with narrow
angles because of the risk of angle closure with mydriasis
o Diagnosis of Horner’s syndrome
 Alpha agonist – not as reliable in direct acting mechanisms
 1% can dilate Horner’s eye more completely than non-Horner’s eye because the
dilator muscle is super sensitive to stimulation
o Adverse effects
 Allergic reactions in 20-50% - hyperemia, increased lacrimation, etc. but it is
more of an irritation response to the drug itself than an immunologic response
 Some alpha-1 stimulation, leading to mydriasis, lid retraction, and conjunctival
blanching
 Systemic effects: dry mouth, fatigue, lethargy, headache, symptoms of head
cold
Brimonidine
o Available in 0.15% or 0.2% or as Alphagan P in 0.1% and 0.15% (P = purite)
o Highly selective alpha-2 adrenergic receptor agonist, most patients do not see any apha1 effects
o Decreased concentration results in fewer side effects while keeping the beneficial
effects
o Antiglaucoma treatment
o MOA
 Decrease aqueous production
 Increase uveoscleral outflow (but probably not due to remodeling)
 May be neuroprotective (inhibit excitotoxicity) in glaucoma patients, method is
not clear
BHS 254.2
Notetaker: Melissa Milbrandt
Clicker Questions
Date: 2/8/2016
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BHS 254.2
Notetaker: Melissa Milbrandt
Date: 2/8/2016
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BHS 254.2
Notetaker: Melissa Milbrandt
Date: 2/8/2016
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