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Phenylephrine

Prescription

Selective Alpha-1 Adrenergic Agonist / Vasopressor

Last reviewed 21 Apr 2026 · PetCare.AI Editorial Team

Species

Dog, Cat

Brands

1 available

Interactions

2 documented

Formulations

Mechanism of action

Pure alpha-1 adrenergic agonist causing peripheral arteriolar vasoconstriction and venous constriction, raising blood pressure via increased SVR. No beta-adrenergic activity — causes reflex bradycardia from baroreceptor activation.

At a glance

Class

Selective Alpha-1 Adrenergic Agonist / Vasopressor

Schedule

Prescription

Storage

Store at room temperature, protect from light

Dosing

🐕

Dog

Used for vasodilatory hypotension (anesthesia-associated, septic shock after flu

Dose

1–3 mcg/kg

Route

IV CRI, Topical (nasal)

Frequency

CRI or bolus as needed

🐈

Cat

Used for anesthetic hypotension in cats

Dose

0.5–3 mcg/kg

Route

IV CRI, Topical

Frequency

CRI

Educational reference only

This information is provided for educational purposes and is not a substitute for professional veterinary advice, diagnosis, or treatment. Always consult a qualified veterinarian before administering any medication to your pet. Find a vet near you →

Formulations

💊

Other — 2

Strength

—

Strength

—

Storage

Store at room temperature, protect from light

Safety

Monitoring parameters

Blood pressure continuouslyHeart rateECGUrine output (renal perfusion)

Educational reference only

Interactions

Major — 1

Acepromazine

major

Acepromazine blocks alpha-1 receptors. Phenylephrine acts primarily on alpha-1 receptors. Acepromazine directly antagonizes phenylephrine's vasopressor effect.

Management: Phenylephrine will be less effective in acepromazine-sedated patients. Higher doses of phenylephrine or alternative vasopressor (vasopressin — V1 receptor, not alpha-1) may be needed.

Moderate — 1

Propranolol

moderate

Phenylephrine (pure alpha-1 agonist) causes vasoconstriction and reflex bradycardia. Propranolol blocks compensatory tachycardia, potentially worsening bradycardia.

Management: Monitor heart rate and blood pressure. The combination predictably causes hypertension + bradycardia.

Educational reference only

Brands

Other markets

Neo-Synephrine

FAQs

Frequently asked questions

›What is Phenylephrine?

Phenylephrine is a selective alpha-1 adrenergic agonist / vasopressor used in pets. Pure alpha-1 adrenergic agonist causing peripheral arteriolar vasoconstriction and venous constriction, raising blood pressure via increased SVR. No beta-adrenergic activity — causes reflex bradycardia from baroreceptor activation.

›What is Phenylephrine used for in pets?

Phenylephrine is used in veterinary medicine for: Used for vasodilatory hypotension (anesthesia-associated, septic shock after flu; Used for anesthetic hypotension in cats.

›What is the Phenylephrine dose for dogs?

For dogs, Phenylephrine is typically dosed as follows — Used for vasodilatory hypotension (anesthesia-associated, septic shock after flu: 1–3 mcg/kg IV CRI/Topical (nasal) CRI or bolus as needed. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.

›What is the Phenylephrine dose for cats?

For cats, Phenylephrine is typically dosed as follows — Used for anesthetic hypotension in cats: 0.5–3 mcg/kg IV CRI/Topical CRI. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.

›Does Phenylephrine need a prescription?

Yes. Phenylephrine is a prescription medication and should only be administered under veterinary supervision.

Educational reference only

References

The PetCare.AI drug reference is built from 13 authoritative sources cited across 580 drug monographs.

Textbooks & handbooks — 5

Plumb's Veterinary Drug Handbook
Withrow & MacEwen's Small Animal Clinical Oncology
Merck Veterinary Manual
NRC Nutrient Requirements of Dogs and Cats
Veterinary Pharmacology and Therapeutics (Riviere & Papich)

Clinical guidelines & consensus — 4

ASPCA Animal Poison Control Center Guidelines
AAHA Diabetes Management Guidelines
ASPCA Poison Control Guidelines
RECOVER CPR Guidelines

Journals & peer-reviewed studies — 2

EPIC Study (J Vet Intern Med 2016)
JVIM FAT CAT Study

Regulatory & approvals — 1

CDSCO Veterinary Drug Approval Registry (1969–2026)

Databases — 1

Washington State University VCPL MDR1 Database