Propranolol
Propranolol Hydrochloride
Also known as: Inderal LA · InnoPran XL · Syprol · AY-64043 · ICI-45520 · NSC-91523 · propranololi hydrochloridum · Propranolol hydrochloride
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Audited v13 dosing evidence
Structured calculator evidenceHypertrophic cardiomyopathy (extra-label)
Verified clinician required
- q12-24h
NA
Governing clinical context (6)
- NOTE: Because of a high first-pass effect after oral dosing, IV dosages are ≈10% of oral dosages. Do not confuse the dosages.
- ■ This medicine can be given with or without food.
- ■ When starting this medicine, your veterinarian may start with a low dose and gradually increase it over time to see how your animal reacts to it. Do not administer more than your veterinarian prescribes.
- ■ Do not suddenly stop giving propranolol to your animal as it can make your animal’s condition worse.
- ■ Your veterinarian will need to monitor your animal closely while it is receiving this medicine. Do not miss these important follow-up visits.
- All propranolol preparations should be stored at room temperature (15°C-30°C [59°F-86°F]) and protected from light. Propranolol solutions will decompose rapidly at alkaline pH.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Propranolol is a non-selective beta-adrenergic antagonist (beta-blocker) used primarily in veterinary medicine for its antiarrhythmic properties. It is classified as a Class II antiarrhythmic agent.
- Primary Uses: Management of supraventricular and ventricular tachyarrhythmias (e.g., APCs, VPCs, atrial fibrillation), hypertrophic cardiomyopathy (HCM), and systemic hypertension.
- Endocrine Uses: Frequently used to control the cardiovascular and neuromuscular signs of sympathetic overstimulation in feline hyperthyroidism and pheochromocytoma.
- Behavioral Uses: Occasionally used off-label for situational anxiety or loud-noise phobias in dogs.
Clinical Pearl: Because propranolol is non-selective, it blocks both cardiac and pulmonary receptors. It should be used with extreme caution or avoided in patients with feline asthma or other bronchospastic airway diseases.
Mechanism of action
Propranolol acts via competitive blockade of both $\beta_1$ and $\beta_2$ adrenergic receptors.
- $\beta_1$ Blockade (Cardiac): $\rightarrow$ Decreases sinus heart rate (negative chronotropy) $\rightarrow$ Depresses AV node conduction (negative dromotropy) $\rightarrow$ Decreases myocardial contractility (negative inotropy) $\rightarrow$ Ultimately reduces cardiac output and myocardial oxygen demand.
- $\beta_2$ Blockade (Pulmonary/Vascular): $\rightarrow$ Can cause bronchoconstriction and peripheral vasoconstriction.
- Additional Effects: Possesses membrane-stabilizing (quinidine-like) effects at higher doses, which alters the cardiac action potential. It lacks intrinsic sympathomimetic activity (ISA) and inhibits glycogenolysis.
Safety & warnings
Contraindications
- Overt heart failure
- Hypersensitivity to beta-blockers
- Greater than 1st degree heart block
- Sinus bradycardia
- Congestive heart failure (unless secondary to a tachyarrhythmia responsive to beta-blockers)
- Bronchospastic lung disease (e.g., feline asthma)
- Bradyarrhythmias
- Acute or decompensated congestive heart failure
- Concurrent administration with alpha-adrenergic agonists (e.g., adrenaline)
Adverse effects
- Bradycardia
- Lethargy and depression
- Impaired AV conduction
- Congestive heart failure (CHF) or worsening of heart failure
- Hypotension
- Syncope
- Diarrhea
- Hypoglycemia
- Bronchoconstriction
- AV block
- Myocardial depression
- Hypoglycaemia
- Bronchospasm
- Diarrhoea
- Peripheral vasoconstriction
Precautions
Use with Caution:
- Patients with significant renal or hepatic insufficiency.
- Patients with sinus node dysfunction.
- Labile diabetic patients (can cause or mask clinical signs of hypoglycemia).
- Digitalized or digitalis-intoxicated patients (severe bradycardia may result).
- May mask clinical signs of thyrotoxicosis.
- Withdrawal: If discontinuing the drug after chronic use, gradual withdrawal is recommended to prevent exacerbation of clinical signs.
Drug interactions
May reduce oral propranolol absorption; separate doses by at least one hour
Additive myocardial depression may occur
May negate cardiac effects of beta-blockers
Concurrent use should be done with caution due to additive negative inotropic effects, particularly in patients with cardiomyopathy or CHF
May decrease the metabolism of propranolol and increase blood levels
May increase risk for hypotension
Unopposed alpha effects of epinephrine may lead to rapid increases in blood pressure and decrease in heart rate
May decrease propranolol metabolism; complete heart block reported in one human
Propranolol may prolong the hypoglycemic effects of insulin therapy
Clearance may be impaired by propranolol
Propranolol doses may need to be decreased when initiating therapy
May increase the metabolism of propranolol
May increase risk for hypotension
May have additive effects with propranolol
Effects may be enhanced with propranolol therapy
May have their actions blocked by propranolol
Effects of theophylline (bronchodilation) may be blocked by propranolol
May decrease the effects of beta blocking agents
Enhanced hypotensive effect
Enhanced hypotensive effect
Enhanced hypotensive effect
Increased risk of bradycardia, severe hypotension, heart failure, and AV block
Potentiates bradycardia
May necessitate a decrease in propranolol dose when initiating therapy
Reduces propranolol absorption
Enhances the effects of the muscle relaxants
Hepatic enzyme induction increases the rate of metabolism of propranolol
Propranolol may enhance the hypoglycaemic effect of insulin
Concurrent use is contraindicated; risk of severe hypertension and bradycardia
Monitoring
- ECG (Electrocardiogram)
- Signs of toxicity (bradycardia, hypotension, lethargy)
- Blood pressure (especially if administering IV)
- Heart rate and rhythm (ECG)
- Signs of congestive heart failure (e.g., respiratory rate/effort)
- Blood glucose (especially in diabetic patients receiving insulin)
Pharmacokinetics
Half-life
Absorption
Well absorbed after oral administration, but undergoes a rapid first-pass effect through the liver, reducing systemic bioavailability to approximately 2-27% in dogs. Hyperthyroid cats may have increased bioavailability compared to normal cats.
Distribution
Highly lipid soluble and readily crosses the blood-brain barrier. Apparent volume of distribution is 3.3-11 L/kg in dogs. Crosses the placenta and enters milk at very low levels. Approximately 90% bound to plasma proteins in humans.
Metabolism
Principally metabolized by the liver. An active metabolite, 4-hydroxypropranolol, has been identified after oral administration.
Elimination
Less than 1% of a dose is excreted unchanged into the urine.
Overdose
Clinical Signs: The most predominant expected signs are hypotension and bradycardia. Other possible effects include CNS depression (ranging from depressed consciousness to seizures), bronchospasm, hypoglycemia, hyperkalemia, respiratory depression, pulmonary edema, AV block, or asystole.
Treatment:
- Decontamination: If recent oral ingestion, consider emptying the gut and administering activated charcoal.
- Monitoring: Monitor ECG, blood glucose, potassium, and blood pressure.
- Cardiovascular Support: Use IV fluids and pressor agents for hypotension. Treat bradycardia with atropine; if atropine fails, cautiously administer isoproterenol. A transvenous pacemaker may be necessary.
- Heart Failure: Treat with digoxin, diuretics, oxygen, and IV aminophylline if necessary.
- Antidotal Therapy: Glucagon (5-10 mg IV; human dose) may increase heart rate and blood pressure, reducing the cardiodepressant effects of propranolol.
- Seizures: Generally respond to IV diazepam.
Available products
Formulations
- Oral Tablets
- Extended/Sustained-Release Capsules
- Injection
- 1 mg/ml injectable solution
- 10 mg tablet
- 40 mg tablet
- 80 mg tablet
- 160 mg tablet
- 5 mg/5 ml oral solution
- 10 mg/5 ml oral solution
- 40 mg/5 ml oral solution
- 50 mg/5 ml oral solution
Human-labeled
- Propranolol HCl Oral Tablets: 10 mg, 20 mg, 40 mg, 60 mg & 80 mg
- Propranolol HCl Extended/Sustained-Release Capsules: 60 mg, 80 mg, 120 mg & 160 mg (Inderal LA, InnoPran XL)
- Propranolol for Injection: 1 mg/mL in 1 mL amps or vials (Inderal)
- Propranolol Oral Solution: 4 mg/mL & 8 mg/mL in 500 mL
- Syprol oral solution
- Propranolol tablets (10 mg, 40 mg, 80 mg, 160 mg)
- Propranolol injection (1 mg/ml)
Regulatory status
Available as POM (Prescription Only Medicine)
Available as POM-V or POM (human generics like Syprol used under the cascade)
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store all propranolol preparations at room temperature (15-30°C) and protect from light. Propranolol solutions will decompose rapidly at alkaline pH.
Client information
- Consistency is Key: To be effective, your pet must receive all doses exactly as prescribed by your veterinarian. Do not abruptly stop this medication without consulting your vet, as it can cause a dangerous rebound effect on the heart.
- What to Watch For: Contact your veterinarian immediately if your pet becomes unusually lethargic, tires easily during exercise, begins wheezing, develops shortness of breath or a cough, or shows a sudden change in behavior or attitude.
- Missed Doses: If you miss a dose, give it as soon as you remember, but never give two doses at once.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.