Propranolol Hydrochloride

Beta-adrenergic receptor antagonist (non-selective beta-blocker) Antihypertensive, antiarrhythmic, antianginal

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog PO 0.2-1 mg/kg (up to 2 mg/kg for refractory arrhythmias) q8h Duration: Variable; often long-term for chronic conditions
Notes: Start at low end and titrate to effect. Monitor heart rate and blood pressure. For behavioral use, doses of 0.5-2 mg/kg q12h have been used.
Cat PO 2.5-5 mg/cat (approximately 0.2-1 mg/kg) q8h Duration: Variable; often long-term
Notes: Titrate based on heart rate and clinical response. Use with caution in cats with asthma or bronchospastic disease.
Horse PO 0.5-1 mg/kg q8h Duration: Variable; often for arrhythmia management
Notes: Bioavailability is low; may need higher doses. Monitor ECG and blood pressure.
Cattle PO 0.5-1 mg/kg q12h Duration: Variable
Notes: Not commonly used; limited data. Use with caution in cattle with respiratory disease.
Small Ruminants (sheep/goats) PO 0.5-1 mg/kg q12h Duration: Variable
Notes: Limited data; use with caution.
Rabbit PO 0.5-1 mg/kg q8-12h Duration: Variable
Notes: Use with caution; rabbits are sensitive to beta-blockers.
Birds/Poultry PO 0.5-2 mg/kg q8-12h Duration: Variable
Notes: Limited data; use with caution.

Clinical Indications & Species Uses

General Indications
  • Management of tachyarrhythmias
  • Control of heart rate in hypertrophic cardiomyopathy
  • Systemic hypertension
  • Adjunct in hyperthyroidism
  • Prevention of migraine (off-label in animals)
Dog (Canine)
  • Hypertension (systemic and portal)
  • Tachyarrhythmias (e.g., supraventricular tachycardia, atrial fibrillation)
  • Hypertrophic cardiomyopathy (adjunctive therapy)
  • Tetralogy of Fallot (to reduce infundibular spasm)
  • Pheochromocytoma (preoperative management)
  • Hyperthyroidism (adjunctive to control tachycardia)
  • Behavioral disorders (e.g., anxiety, aggression) - off-label
Cat (Feline)
  • Hypertrophic cardiomyopathy (to reduce heart rate and outflow obstruction)
  • Tachyarrhythmias (e.g., supraventricular tachycardia)
  • Hypertension (adjunctive therapy)
  • Hyperthyroidism (adjunctive to control tachycardia)
  • Anxiety-related disorders (off-label)
Horse (Equine)
  • Tachyarrhythmias (e.g., atrial fibrillation, ventricular tachycardia)
  • Hypertension (e.g., associated with laminitis)
  • Exercise-induced pulmonary hemorrhage (prophylaxis - controversial)
  • Anxiety/behavioral issues (off-label)
Cattle (Bovine)
  • Tachyarrhythmias (e.g., traumatic pericarditis, myocarditis)
  • Hypertension (rarely used)
  • Milk fever (adjunctive therapy - experimental)
Small Ruminants (Sheep / Goat)
  • Tachyarrhythmias (rarely used)
  • Hypertension (rarely used)
Rabbit & Small Mammals
  • Cardiac disease (e.g., hypertrophic cardiomyopathy, arrhythmias)
  • Hypertension (rarely used)
Avian & Poultry
  • Tachyarrhythmias (rarely used)
  • Hypertension (rarely used)
Exotic & Other Species
  • Reptiles: cardiac arrhythmias (rarely used)
  • Small mammals (ferrets, guinea pigs): cardiac disease (off-label)

Pharmacology & Mechanism of Action

Drug Class: Beta-adrenergic receptor antagonist (non-selective beta-blocker) | Pharmacological Group: Antihypertensive, antiarrhythmic, antianginal

Mechanism of Action: Propranolol is a competitive, non-selective beta-adrenergic receptor antagonist that blocks both beta-1 and beta-2 receptors. By blocking beta-1 receptors in the heart, it reduces heart rate, myocardial contractility, and cardiac output, thereby decreasing myocardial oxygen demand. Beta-2 blockade leads to bronchoconstriction, peripheral vasoconstriction, and inhibition of glycogenolysis. It also has membrane-stabilizing (quinidine-like) effects at high doses, contributing to its antiarrhythmic properties. Central nervous system effects include reduction of sympathetic outflow, which may contribute to its antihypertensive action.

Pharmacodynamics: Propranolol produces a dose-dependent decrease in heart rate and contractility, leading to reduced cardiac output and blood pressure. It suppresses sinus node automaticity, slows atrioventricular conduction, and increases the refractory period of the AV node. It also reduces renin release from the juxtaglomerular apparatus, decreasing angiotensin II and aldosterone levels. In the eye, it reduces aqueous humor production, lowering intraocular pressure. Beta-2 blockade can cause bronchoconstriction and mask signs of hypoglycemia (tachycardia, tremors) in diabetic animals.

⚡ Pharmacokinetics Summary

Absorption: Propranolol is well absorbed after oral administration in most species, but undergoes extensive first-pass hepatic metabolism, resulting in variable systemic bioavailability. In dogs, oral bioavailability is approximately 30-40% due to first-pass effect. In horses, absorption is rapid but bioavailability is low (around 10-20%).
Distribution: Propranolol is highly lipophilic and distributes widely throughout the body, including the brain, heart, lungs, and kidneys. It crosses the placenta and is excreted in milk. Volume of distribution is large (about 4-6 L/kg in dogs).
Metabolism: Extensively metabolized in the liver via oxidation, glucuronidation, and ring hydroxylation. Major metabolites include 4-hydroxypropranolol, which has some beta-blocking activity. Hepatic metabolism is saturable, leading to non-linear kinetics at higher doses.
Excretion: Metabolites are primarily excreted in urine (about 90%), with the remainder in feces. Less than 1% of the parent drug is excreted unchanged in urine. In animals with hepatic impairment, clearance is reduced.
Half-Life: Dog: 1-2 hours; Cat: 2-4 hours; Horse: 1-2 hours; Cattle: 2-3 hours (estimated); Rabbit: 1-2 hours (estimated).
Bioavailability: Oral bioavailability is low and variable due to first-pass metabolism: Dog ~30-40%, Cat ~50-60% (estimated), Horse ~10-20%, Cattle ~20-30% (estimated).
Protein Binding: Propranolol is approximately 90-95% bound to plasma proteins in dogs and cats, primarily to albumin and alpha-1-acid glycoprotein.

Available Formulations & Strengths

Oral Tablet 10 mg, 20 mg, 40 mg, 60 mg, 80 mg (PO)
Oral Extended-Release Capsule 60 mg, 80 mg, 120 mg, 160 mg (PO)
Oral Solution 4 mg/mL, 8 mg/mL (PO)
Injectable Solution 1 mg/mL (for IV use) (IV)

Contraindications & Clinical Warnings

Contraindications:
  • Known hypersensitivity to propranolol or other beta-blockers
  • Severe bradycardia or heart block (second- or third-degree AV block)
  • Cardiogenic shock or decompensated heart failure
  • Severe bronchospastic disease (e.g., asthma, COPD)
  • Sick sinus syndrome
  • Uncontrolled congestive heart failure (unless specifically indicated for HCM with careful monitoring)
  • Concurrent use of MAO inhibitors (except with extreme caution)
  • In animals with pheochromocytoma, do not use alone; must combine with an alpha-blocker (e.g., phenoxybenzamine) to avoid unopposed alpha-mediated vasoconstriction
Warnings & Clinical Precautions:
  • Use with caution in animals with diabetes mellitus; beta-blockade may mask signs of hypoglycemia (tachycardia, tremors) and impair glucose recovery.
  • Use with caution in animals with hepatic impairment; dose reduction may be necessary.
  • Use with caution in animals with renal impairment; monitor renal function.
  • Do not discontinue abruptly; taper dose over 1-2 weeks to avoid rebound tachycardia, hypertension, or exacerbation of angina.
  • In animals with hyperthyroidism, beta-blockers may mask signs of thyrotoxicosis; monitor thyroid status.
  • Use with caution in animals with peripheral vascular disease (e.g., Raynaud's phenomenon) as beta-blockade can exacerbate vasoconstriction.
  • In horses, use with caution in those with respiratory disease; beta-2 blockade can cause bronchoconstriction.
  • In cats, use with caution in those with asthma or chronic bronchitis.
  • May cause bradycardia and hypotension; monitor heart rate and blood pressure regularly.
  • In lactating animals, propranolol is excreted in milk; use with caution in nursing mothers.
  • In food animals, observe withdrawal times; extra-label use requires veterinary oversight.

Adverse Effects & Reactions

Common:

  • Bradycardia
  • Hypotension
  • Lethargy or fatigue
  • Gastrointestinal disturbances (vomiting, diarrhea)
  • Bronchoconstriction (especially in animals with respiratory disease)
  • Masking of hypoglycemia signs

Serious / Severe:

  • Severe bradycardia or AV block
  • Congestive heart failure (precipitated or worsened)
  • Bronchospasm (severe)
  • Hypoglycemia (especially in neonates or diabetic animals)
  • Peripheral vasoconstriction (cold extremities, cyanosis)
  • Mental depression or behavioral changes

Rare:

  • Hepatotoxicity (elevated liver enzymes)
  • Blood dyscrasias (thrombocytopenia, agranulocytosis)
  • Alopecia
  • Ocular effects (dry eyes, blurred vision)
  • Peyronie's disease (in humans; not reported in animals)

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Calcium channel blockers (e.g., diltiazem, verapamil) Additive negative chronotropic and inotropic effects; risk of severe bradycardia, AV block, and heart failure. High
Digoxin Additive bradycardia and AV conduction delay; increased risk of digoxin toxicity due to reduced renal clearance. Moderate
Antiarrhythmics (e.g., amiodarone, lidocaine) Additive cardiac depression; increased risk of bradycardia and arrhythmias. Moderate
Sympathomimetics (e.g., epinephrine, norepinephrine) Unopposed alpha-adrenergic effects leading to severe hypertension and bradycardia. High
NSAIDs (e.g., indomethacin) Reduced antihypertensive effect due to inhibition of prostaglandin synthesis. Mild
Phenobarbital or other hepatic enzyme inducers Increased metabolism of propranolol, reducing its efficacy. Moderate
Cimetidine Decreased hepatic metabolism of propranolol, increasing its plasma levels and risk of toxicity. Moderate
Insulin or oral hypoglycemics Beta-blockade may mask hypoglycemia symptoms and impair glucose recovery; may enhance hypoglycemic effect. Moderate
Alpha-2 agonists (e.g., xylazine, dexmedetomidine) Additive bradycardia and hypotension; risk of severe cardiovascular depression. High

Overdose & Toxicity Management

Signs of Toxicity:

  • Severe bradycardia
  • Hypotension
  • Cardiac arrest
  • Bronchospasm
  • Hypoglycemia
  • Seizures (in severe cases)
  • Depression of central nervous system
  • Pulmonary edema (in severe cases)

Emergency Treatment Protocol: Treatment is symptomatic and supportive. Induce emesis if recent oral ingestion and animal is conscious. Administer activated charcoal to reduce absorption. For bradycardia and hypotension, administer atropine (0.04 mg/kg IV) and fluids. If unresponsive, consider glucagon (50-150 mcg/kg IV bolus followed by continuous rate infusion) which has positive inotropic and chronotropic effects independent of beta-receptors. For severe bronchospasm, use bronchodilators (e.g., albuterol, aminophylline). For hypoglycemia, administer dextrose. In severe cases, consider temporary cardiac pacing. Monitor ECG, blood pressure, and blood glucose closely.

Food Animal Withdrawal Times

🥩 Meat: 7 days🥛 Milk: 3 days

Withdrawal times are not officially established for propranolol in food animals. The values provided are conservative estimates based on pharmacokinetic data and should be used as a guide. Always consult with a veterinary pharmacologist and adhere to local regulations. Extra-label use in food animals requires a valid veterinary-client-patient relationship and extended withdrawal times.

Storage, Handling & Regulatory Information

Storage Temperature: Store at controlled room temperature 20-25°C (68-77°F); excursions permitted between 15-30°C (59-86°F).

Light Sensitivity: Light-sensitive — protect from direct exposure.

Handling & Special Conditions: Protect from light and moisture. Keep in a tightly closed container. Do not freeze oral solution.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Not FDA-approved for veterinary use; approved for human use. However, it is commonly used in veterinary medicine as an extra-label drug.

Extra-Label (Off-Label) Use: Propranolol is not FDA-approved for use in animals; it is used extra-label under the Animal Medicinal Drug Use Clarification Act (AMDUCA). Extra-label use requires a valid veterinary-client-patient relationship, and for food animals, a withdrawal time must be established. Propranolol is not listed as a prohibited drug in food animals, but its use must be carefully managed to avoid violative residues.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Propranolol is a non-selective beta-blocker used in veterinary medicine primarily for the management of tachyarrhythmias, hypertrophic cardiomyopathy (especially in cats), and systemic hypertension. It is also used as an adjunct in hyperthyroidism and pheochromocytoma. Due to its non-selective beta-blockade, it can cause bronchoconstriction and mask hypoglycemia, so it should be used with caution in animals with respiratory disease or diabetes. Dosing must be individualized, starting at the low end of the dose range and titrating based on heart rate and clinical response. Abrupt discontinuation should be avoided to prevent rebound effects. In food animals, extra-label use requires careful attention to withdrawal times. Propranolol is available in various oral formulations and an injectable solution for IV use. Monitoring of heart rate, blood pressure, and clinical signs is essential during therapy. For animals with concurrent conditions, consider alternative beta-blockers (e.g., atenolol, metoprolol) that are more cardioselective.

References & Literature

  • 📚 Plumb's Veterinary Drug Handbook
  • 📚 Papich Veterinary Pharmacology and Therapeutics
  • 📚 Compendium of Veterinary Products (CVP)