Isoproterenol
Isoproterenol hydrochloride
Also known as: Isuprel · Imuprel · Isolin · Lenoprel · Norisodrine Aerotrol · Proterenal · Saventrine · Vapo-iso · Isoprenaline hydrochloride · Isopropylarterenol hydrochloride · Isopropylnoradrenaline hydrochloride
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Sinoatrial arrest, sinus bradycardia, complete AV block | 0.4 mg in 250 mL D5W drip slowly to effect | IV | to effect | — | 🌎 NA |
| Sinoatrial arrest, sinus bradycardia, complete AV block | Isuprel Glossets 5-10 mg | sublingual or rectal | q4-6h | — | 🌎 NA |
| Sinoatrial arrest, sinus bradycardia, complete AV block | 0.04-0.08 micrograms/kg/min | IV | CRI | — | 🌎 NA |
| Sinoatrial arrest, sinus bradycardia, complete AV block | 0.1-0.2 mg | IM, SC | q4h | — | 🌎 NA |
| Sinoatrial arrest, sinus bradycardia, complete AV block | 0.4 mg in 250 mL D5W slowly | IV | slowly | — | 🌎 NA |
| Adjunctive treatment for bradycardia associated with calcium channel blocker overdose | Mix 0.4 mg in 250 mL of D5W and give via slow IV drip to effect. | IV | to effect | — | 🌎 NA |
- Sinoatrial arrest, sinus bradycardia, complete AV block: Infusion
- Adjunctive treatment for bradycardia associated with calcium channel blocker overdose: Alternative to atropine
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Sinoatrial arrest, sinus bradycardia, complete AV block | 0.4 mg in 250 mL D5W drip slowly to effect | IV | to effect | — | 🌎 NA |
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Short-term bronchodilatation | Dilute 0.2 mg in 50 mL of saline and administer 0.4 micrograms/kg as an IV infusion, monitor heart rate continuously and discontinue when heart rate doubles. | IV | once | Effects may only last for an hour | 🌎 NA |
- Short-term bronchodilatation: ARCI UCGFS Class 2 Drug
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Isoproterenol is a potent, non-selective beta-adrenergic agonist used primarily in emergency veterinary medicine.
Key clinical features include:
- Cardiac Support: Used to treat severe bradyarrhythmias, such as complete AV block or sinoatrial arrest, by increasing heart rate and contractility.
- Bronchodilation: Historically used for acute bronchial constriction, though largely replaced by more selective $\beta_2$ agonists (like terbutaline or albuterol) to avoid cardiac side effects.
- Shock/Heart Failure: Occasionally used as adjunctive therapy, but its use is limited due to its strong arrhythmogenic potential and tendency to cause tachycardia.
Clinical Pearl: Because of its profound cardiostimulatory properties and the availability of safer, more targeted therapies (e.g., pacemakers for AV block, selective bronchodilators for asthma), isoproterenol is now infrequently used. It has a very short duration of action, meaning adverse effects dissipate quickly once the infusion is stopped.
Mechanism of action
Isoproterenol is a synthetic sympathomimetic amine that acts as a potent, non-selective agonist at both $\beta_1$ and $\beta_2$ adrenergic receptors, with virtually no $\alpha$-adrenergic activity.
Mechanism Pathway: Drug binds to $\beta_1$ and $\beta_2$ receptors → activates Gs-proteins → stimulates adenylyl cyclase → increases intracellular cyclic-AMP (cAMP) → activates Protein Kinase A (PKA).
- Cardiac Effects ($\beta_1$): Increased cAMP leads to increased intracellular calcium influx → positive inotropy (increased contractility) and positive chronotropy (increased heart rate and pacemaker discharge rate).
- Smooth Muscle Effects ($\beta_2$): Increased cAMP inhibits myosin light-chain kinase (MLCK) → relaxation of bronchial smooth muscle (bronchodilation) and peripheral vasculature (vasodilation).
- Immunologic Effects: Inhibits the antigen-mediated release of histamine and slow-releasing substance of anaphylaxis (SRS-A).
Safety & warnings
Contraindications
- Tachycardias or AV block caused by cardiac glycoside (digoxin) intoxication
- Ventricular arrhythmias that do not require increased inotropic activity
Adverse effects
- Tachycardia
- Ventricular arrhythmias (highly arrhythmogenic)
- Anxiety and excitability
- Tremors
- Headache
- Weakness
- Vomiting
Precautions
Warning: Isoproterenol is highly arrhythmogenic (more so than dopamine or dobutamine). Use with extreme caution.
- Disease States: Use with caution in patients with coronary insufficiency, hyperthyroidism, renal disease, hypertension, or diabetes.
- Shock: Isoproterenol is not a substitute for adequate fluid replacement in shock.
- Pregnancy: FDA Category C. Animal studies show adverse fetal effects. Use cautiously as a last resort when benefits clearly outweigh risks.
- Lactation: Rapidly deactivated in the gut, so it is unlikely to pose much risk to nursing offspring.
Drug interactions
Increased risk of developing arrhythmias. Propranolol may be administered should these occur.
May antagonize isoproterenol's cardiac, bronchodilating, and vasodilating effects. Can be used to treat isoproterenol-induced tachycardia, but use with caution in bronchospastic disease.
Increased risk of arrhythmias.
Hypertension may result if used concurrently.
Should not be administered concurrently as increased toxicity may result.
May increase the risk for theophylline toxicity.
Monitoring
- Cardiac rate and rhythm (ECG continuous monitoring highly recommended)
- Respiratory rate and auscultation (especially during anaphylaxis)
- Blood pressure
- Blood gases (if indicated and possible)
- Urine flow (if possible)
Pharmacokinetics
Absorption
Rapidly inactivated by the GI tract. Sublingual administration is not reliably absorbed (effects may take up to 30 minutes). IV administration results in immediate effects, but only persists for a few minutes after discontinuation.
Distribution
Unknown if distributed into milk. Pharmacologic actions are ended primarily through tissue uptake.
Metabolism
Metabolized in the liver and other tissues by catechol-O-methyltransferase (COMT) to a weakly active metabolite.
Elimination
Primarily cleared via tissue uptake and enzymatic metabolism (COMT).
Overdose
High doses may cause an initial hypertension, followed by hypotension, as well as severe tachycardias and other arrhythmias.
Treatment:
- Halt or reduce the drug infusion (effects dissipate rapidly due to short half-life).
- Provide supportive care.
- If tachycardias persist, a beta-blocker could be considered for treatment, provided the patient does not have a bronchospastic disease.
Available products
Formulations
- Injection
- Sublingual tablets (historical)
- Rectal suppositories (historical)
Human-labeled
- Isoproterenol HCl for Injection: 1:5000 solution (0.2 mg/mL) 5 mL & 10 mL vials
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store in tight, light-resistant containers. Stable indefinitely at room temperature. Salts will darken with time upon exposure to air, light, or heat. Solutions may become pink or brownish-pink if exposed to air, alkalies, or metals. Do not use solutions that are discolored or contain a precipitate. If mixed with other drugs/fluids resulting in a pH > 6, use immediately.
Client information
Important Information for Pet Owners
- Emergency Use Only: Isoproterenol is a potent, fast-acting emergency medication. It is only administered by trained veterinary professionals in a hospital setting where your pet's heart rate and blood pressure can be continuously monitored.
- Purpose: It is typically used as a life-saving measure to treat dangerously slow heart rates (heart block) or, rarely, severe asthma crises.
- Rapid Action: The drug works immediately but wears off within minutes once the IV drip is stopped. This allows the veterinarian to precisely control the effects.
- Side Effects: Because it strongly stimulates the heart, it can cause a rapid heart rate, anxiety, or tremors. The veterinary team will monitor closely for these and adjust the dose instantly if needed.
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.