Lecture 11 - Phenylephrine Flashcards
What receptors causes mydriatic, anti-glaucoma, vasoconstrictor/decongestant effects?
- mydriatic (a1 agonist)
- anti-glaucoma (a1, a2, b2 agonists)
- vasoconstrictors - a1 agonists
Describe applications of Norepinephrine
clinical usage (if any), what receptors it activated, impact on blood vessels
- little clinical use (gets used up quickly)
- a1, a2 and b1 receptors
- good systemic vasocontriction
Describe applications of Epinephrine (prototyical adrenergic agonist)
(clinical usage (if any), what receptors it activated, impact on blood vessels)
- potent vasoconstrictor
- weak mydriatic
- decreases IOP - antiglaucoma (open angle)
- a and b receptors may play role
Describe Phenylepinephrine
drug name, what receptors it activated, cyclopegia effects?, effect on drug with dark irides
- Neo-Synephrine
- mainly a1 agonist
- no cycloplegia effects, has active light reflex
- sympathetic tone decreases with age
- drug effect decreases with dark irides
- increased effect with local anesthetics
What are some clinical uses of Phenylephrine
- counteracts miosis
- treats ptosis from sympathetic denervation
- diagnosis Horners (not very reliable)
- breaks posterior synechia
- treat miotic cysts from Ach-esterase inhibitors
What is contraindicated for Phenylephrine?
Thryroid, Heart, Blood Pressure
- Thyrotoxicosis (sudden release of thryoid hormone responds to phenylephrine and drastically increases blood pressure)
- Coronary artery disease
- Hypertension
What drugs have interactions with Phenylephrine?
Select 4
- Tricyclic anti-depressants
- MAO inhibitors
- Guanethidine
- reserpine
What are the CNS toxicities of phenylephrine?
Pick 2
- CNS stimulation
- headaches
What are the cardiovascular toxicities of phenylephrine?
think how SNS agonist affects blood pressure
- hypertension
- subarachnoid hemorrhage
- ventricular arrhythmias
- tachycardia
- reflex bradycardia
- blanching of skin
What are the ocular toxicities of phenylephrine?
think how SNS agonist affects eyes
- transient pain and excess lacrimation
- keratitis
- liberation of iris pigment (floaters, patient with dark irides)
- post-dilation miosis in older patients (constriction of iris)
- rebound congestion
- conjuctival hypoxia (vasoconstriction)
- angle closure
Which drug class is not contraindicated for Phenylephrine?
A. Tricyclic antidepressants B. MOA inhibitors C. Guanethidine D. Reserpine E. All of the above
E. All of the above
A. Tricyclic antidepressants
B. MOA inhibitors
C. Guanethidine
D. Reserpine
Which is NOT a cardiovascular toxicity of phenylephrine?
A. Hypotension B. Reflex Bradycardia C. Blanching of Skin D. Subarachnoid Hemorrhage E. Ventricular arrhythmias
A. Hypotension
Which is NOT a ocular toxicity of phenylephrine?
A. Excess lacrimation from pain B. Conjuntival Hypoxia C. Blurry vision D. Keratitis E. Angle closure
C. Blurry vision
