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Phenoxybenzamine

Prescription
Alpha-adrenergic blocker (irreversible, non-selective)
Last reviewed 19 Apr 2026 · PetCare.AI Editorial Team
Species
Dog, Cat
Brands
2 available
Interactions
1 documented
Formulations
1

Mechanism of action

Irreversibly blocks alpha-1 and alpha-2 adrenergic receptors, relaxing smooth muscle in the urethral sphincter and prostate

At a glance

Class
Alpha-adrenergic blocker (irreversible, non-selective)
Schedule
Prescription
Storage
Store below 25°C, protect from light

Dosing

🐕

Dog

Functional urethral obstruction / Urethral sphincter hypertonus
Dose
0.25–0.5 mg/kg
Route
PO
Frequency
BID to TID
Max dose
20 mg/dose; 40 mg/day
Duration: Short- to medium-term; onset 24–48h
🐈

Cat

Feline urethral obstruction (post-unblocking) / Urethral spasm
Dose
0.25–0.5 mg/kg
Route
PO
Frequency
BID
Max dose
5 mg/dose; 10 mg/day
Duration: 5–14 days post-catheter removal
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

💊

Capsule — 1

Strength
10mg
Available in India

Storage

Store below 25°C, protect from light

Safety

Absolute contraindications — do not use

  • Hypotension

Use with caution

  • Cardiac disease
    May cause reflex tachycardia

Adverse effects

Common
Hypotension
Tachycardia
Miosis
Nasal congestion
Serious
Severe hypotension
Syncope

Monitoring parameters

Blood pressureHeart rateUrination pattern
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 →

Interactions

Major — 1

Acepromazine
major
Both are alpha-adrenergic blockers; combined use may cause severe refractory hypotension
Management: Avoid concurrent use. If sedation needed, use alternative sedative (trazodone, gabapentin).
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 →

Brands

International

Dibenzyline
Concordia

India

Fenoxene
Samarth Pharma

FAQs

Frequently asked questions

›What is Phenoxybenzamine?
Phenoxybenzamine is a alpha-adrenergic blocker (irreversible, non-selective) used in pets. Irreversibly blocks alpha-1 and alpha-2 adrenergic receptors, relaxing smooth muscle in the urethral sphincter and prostate
›What is Phenoxybenzamine used for in pets?
Phenoxybenzamine is used in veterinary medicine for: Functional urethral obstruction / Urethral sphincter hypertonus; Feline urethral obstruction (post-unblocking) / Urethral spasm.
›What is the Phenoxybenzamine dose for dogs?
For dogs, Phenoxybenzamine is typically dosed as follows — Functional urethral obstruction / Urethral sphincter hypertonus: 0.25–0.5 mg/kg PO BID to TID. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.
›What is the Phenoxybenzamine dose for cats?
For cats, Phenoxybenzamine is typically dosed as follows — Feline urethral obstruction (post-unblocking) / Urethral spasm: 0.25–0.5 mg/kg PO BID. Always consult your veterinarian for a dose tailored to your pet's weight, age, and condition.
›What are the side effects of Phenoxybenzamine?
Common: Hypotension, Tachycardia, Miosis, Nasal congestion. Serious (call your vet immediately): Severe hypotension, Syncope.
›Does Phenoxybenzamine need a prescription?
Yes. Phenoxybenzamine is a prescription medication and should only be administered under veterinary supervision.
›When should Phenoxybenzamine not be used?
Do not use Phenoxybenzamine if: Hypotension.
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 →

References

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
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