View source for Phenylephrine

==General==
*Type: [[Vasopressors]]
*Dosage Forms: Commonly 50 mg per 5 mL (10 mg/mL)
*Common Trade Names: Neosynephrine
*Onset of action: About 1 minute
*Duration of action: 10-20 minutes

==Adult Dosing==
===Hypotension===
*Start 100-200 mcg/min then taper down
**40-60 mcg/min works for most

*"[[Push dose pressors|Push dose]]"
**Inject 1 mL (10 mg) into 100 mL NS Bag = 100 mcg/mL
**Draw this into a syringe, with a concentration of 100mcg/mL
**Administer 0.5-2 mL (50-200 mcg) every 2-5 minutes

===Low Flow [[Priapism]]===
*Dilute phenylephrine 1mg in 9mL NS for final concentration of 100mcg/mL 
**For 500 mcg/ml, take 0.5 ml of 10mg/ml phenylephrine, and dilute in 9.5 cc NS
*Inject base of penis with 29-Ga needle (after blood aspiration to confirm position) 
**100-500 mcg every 3-5min (max 1000 mcg) until resolution or 1 hour

==Pediatric Dosing==
*Hypotension/Shock
**IV Bolus: 5-20mcg/kg q10-15min prn, 1st dose should not exceed 500mcg with a max dose of 1000mcg
**IV Infusion: 0.1-0.5mcg/kg/min, titrate to desired BP
*Nasal Congestion (OTC)
**4-<6yrs: 2.5mg q4hr prn for <7 days
**6-<12yrs: 5mg q4hr prn for <7 days

==Special Populations==
*[[Drug Ratings in Pregnancy|Pregnancy Rating]]: C
*Lactation: infant risk cannot be ruled out
*Renal Dosing
**Adult
**Pediatric
*Hepatic Dosing
**Adult
**Pediatric

==Contraindications==
*Allergy to class/drug
*Severe [[hypertension]]
*[[Ventricular tachycardia]]
*[[Closed angle glaucoma]]
*Caution if:
**[[Heart failure]] or [[cardiogenic shock]] (cardiac output may decrease with increased SVR)
**[[Spinal cord injury]] or other autonomic dysfunction (may experience exaggerated increase in blood pressure)
**[[Hyperthyroidism]]

==Adverse Reactions==
*Baroreceptor-mediated reflex bradycardia, particularly in patients with preexisting cardiac dysfunction or severe CAD
*If extravasates use phentolamine

===Serious===
*[[Bradycardia]]
*[[Pulmonary edema]]
*[[Metabolic acidosis]]
*Decreased renal perfusion
*Extravasation

===Common===
*[[Hypertension]]
*[[Anxiety]]
*[[Headache]]
*Rebound congestion, sneezing
*[[Nausea]], gastric irritation

==Pharmacology==
*Half-life: 2.5 hours
*Metabolism: extensively in intestinal wall, moderately in liver
*Excretion: Urinary
*Mechanism of Action: selective α<sub>1</sub> agonist causes vasoconstriction
===Primary Receptor===
*α<sub>1</sub>
===Relative Effects===
*↑SVR
*↓HR (reflex bradycardia)

==Notes==
*Use with caution in patients with spinal cord injury-related bradycardia 
*Useful for treatment of vasodilatory shock when norepinephrine or [[dopamine]] have precipitated tachyarrhythmias
*In patients with ↓LV function, unopposed α<sub>1</sub> may lead to decreased CO or myocardial ischemia
**However clinical trials do not support these effects when used in clinically appropriate dose range
*Commonly used as an alternative to norepinephrine in the setting of [[atrial fibrillation]] with rapid ventricular response (associated with lower heart rate after initiation of vasopressor) <ref>Law AC, Bosch NA, Peterson D, Walkey AJ. Comparison of Heart Rate After Phenylephrine vs Norepinephrine Initiation in Patients With Septic Shock and Atrial Fibrillation. Chest. 2022;162(4):796-803. doi:10.1016/j.chest.2022.04.147</ref>
===Indication===

*Neurogenic Shock
*Second line agent for septic shock

==See Also==
*http://www.atsjournals.org/doi/abs/10.1164/rccm.201006-0972CI?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%3dpubmed#readcube-epdf

==References==
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[[Category:Pharmacology]] [[Category:Critical Care]]