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BHS 254.2 Notetaker: Melissa Milbrandt Date: 2/8/2016 Page1 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 o o o Date: 2/8/2016 Page2 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 Page3 BHS 254.2 Notetaker: Melissa Milbrandt Date: 2/8/2016 Page4 BHS 254.2 Notetaker: Melissa Milbrandt Date: 2/8/2016 Page5