Isoproterenol (Isuprel)

ED / ICU / Transport

• Symptomatic bradycardia or AV block refractory to atropine: sinus node dysfunction or second- or third-degree AV block with hypotension or poor perfusion. Use it in patients at low likelihood of coronary ischemia. It is a bridge to transcutaneous or transvenous pacing. That use is off-label under current PLR-format labels. Some older-format labels, including Hospira's Isuprel, still list heart block and Adams-Stokes attacks.
• Recurrent pause-dependent torsades de pointes: acquired long QT with bradycardia or pauses, recurring despite IV magnesium. The drug raises the rate and shortens the QT. Use it with expert input, as an alternative or bridge to overdrive pacing (off-label).
• Electrical storm in Brugada syndrome, idiopathic VF or early repolarization syndrome: Specialists direct this. The goal is suppressing recurrent VF (off-label).
• Shock with low cardiac output or distributive shock: The FDA label covers improving hemodynamics. Few clinicians reach for it now, because it lowers diastolic and mean pressure.
• Bronchospasm during anesthesia: The FDA label covers an IV bolus.

Other Uses

• Beta-blocker overdose with refractory bradycardia: Adjunct only, with toxicology input. The 2025 AHA Guidelines for CPR and ECC, Part 10, lists vasopressors (COR 1) and high-dose insulin for hypotension refractory to vasopressors (COR 1). Glucagon is COR 2a. VA-ECMO for cardiogenic shock refractory to drugs is COR 2a. Calcium is COR 2b. Lipid emulsion has uncertain usefulness (COR 2b) (off-label).
• Electrophysiology (EP) lab and diagnostic testing: Used for provoking arrhythmias during an EP study and for testing the level of AV block. Follow the lab's own protocol (off-label).

Doses vary by protocol; follow local protocols and medical direction.

Available Forms

• Injection: 0.2 mg/mL (200 mcg/mL) in 1 mL (0.2 mg) and 5 mL (1 mg) single-dose vials or ampuls (Isuprel and generics). Must be diluted before use. Some products contain sodium metabisulfite

Adult Dosing

Dosing weight: Adult doses don't use weight. They're written in mcg/min.

Pediatric Dosing

Continuous Infusion

Preparation & Administration

• Infusion dilution (label): 5 mL (1 mg) in 500 mL D5W = 2 mcg/mL. At that strength, 10 mcg/min runs at 300 mL/hr and 20 mcg/min at 600 mL/hr. The label also notes that concentrations up to 10 times stronger have been used when volume must be limited.
• Bolus dilution (label): 1 mL (0.2 mg) diluted to 10 mL with 0.9% NaCl or D5W = 20 mcg/mL.
• Use and inspection: use diluted solution immediately. Do not use if pinkish, darker than slightly yellow, or with a precipitate.
• Pump: infusion pump only, with the drug library set to the actual concentration; no free flow.
• Line: dedicated line or lumen so flushes do not bolus the drug.

Contraindications

• Tachycardia or tachyarrhythmias (label).
• Ventricular arrhythmias (label), except as specialist therapy for recurrent pause-dependent torsades (acquired long QT) or for electrical storm in Brugada syndrome, early repolarization syndrome or idiopathic VF.
• Angina pectoris (label) and acute coronary syndrome, per the 2022 ESC guideline.
• Congenital long QT syndrome, per the 2022 ESC guideline. Adrenergic stimulation can trigger torsades.
• Tachycardia or heart block from digitalis toxicity (older labels): treat with digoxin immune fab instead.

Precautions

• Coronary artery disease or cardiomyopathy: Arrhythmias and ischemia become more likely.
• Hypovolemia: Replace volume first. Vasodilation can drop the pressure.
• Organic AV node disease: Older labels report that heart block or Adams-Stokes attacks can paradoxically worsen. Have pacing ready.
• Sulfite sensitivity: Some products contain sodium metabisulfite. That doesn't rule out emergency use.
• Potent inhaled anesthetics such as halothane: avoid the combination (arrhythmias).

Hold / Reassess If

• Heart rate above the goal set by the prescriber (shock dosing per label: consider reducing or pausing above 110/min): reduce the rate.
• Heart rate above 130/min, new or increasing PVCs, or VT: reduce or stop; ventricular arrhythmia risk rises at these rates.
• Chest pain or new ST changes: reduce or stop; 12-lead ECG.
• MAP or diastolic pressure below goal: reduce, give volume, or switch to epinephrine (stop isoproterenol first; do not run both together).
• No rate response at the top of the range: pace rather than escalate.

Common

Nobody has established how often these happen. The labels only list voluntary reports.

• Tachycardia and palpitations
• Nervousness, mild tremor, weakness, headache, dizziness, blurred vision
• Flushing, sweating, pallor
• Nausea
• Blood pressure changes: vasodilation usually drops the diastolic and mean pressure. The systolic may rise or stay the same. Both hypotension and hypertension have been reported.

Serious / Life-Threatening

Overdose & Toxicity Management

• Signs: tachycardia or other arrhythmias, palpitations, angina, hypotension or hypertension.
• Immediate: Reduce the rate or stop until the patient is stable. The effect fades within minutes. Monitor blood pressure, pulse, respirations and ECG.
• Antidote: There isn't one. Treat arrhythmias per ACLS/PALS. Dialyzability is unknown.

Clinically Significant Interactions

IV Compatibility

• Diluents (label): D5W for infusion; 0.9% NaCl or D5W for bolus dilution.
• Dedicated line or lumen: no boluses or flushes through the isoproterenol line.
• Discard any solution that is pink, darker than slightly yellow or has a precipitate.
• Verify with an institutional compatibility resource.

• Pediatrics: Not established. Specialists only (see the Pediatric Dosing table). IV use in refractory asthma has caused deaths, and the risk climbs with acidosis, hypoxemia, corticosteroids or methylxanthines. If it's used, the label calls for continuous vital signs, frequent ECGs and daily CK-MB.
• Pregnancy: Decades of published use show no drug-associated risk of major birth defects or miscarriage. Untreated shock or bradycardia endangers mother and fetus, so don't withhold indicated therapy. Avoid it during the second stage of labor, since it may inhibit contractions and delay delivery. The label also says to avoid it in obstetrics when maternal blood pressure is above 130/80 mmHg. It warns of uterine vasoconstriction, reduced uterine blood flow, uterine atony with hemorrhage and fetal anoxia.
• Lactation: There are no data on transfer into human milk. The short half-life makes infant exposure likely very low.
• Older Adults: They may respond less to β stimulation (label). Start at the low end of the range and watch for ischemia. It isn't on the AGS Beers Criteria.
• Renal Impairment: No specific adjustment has been established. Titrate to effect.
• Hepatic Impairment: No specific adjustment has been established. Titrate to effect.
• Obesity / Dosing Weight: Adult doses are in mcg/min, not weight-based. Pediatric mcg/kg/min dosing has no labeled guidance. Pick one institutional dosing weight and document it.
• Heart Transplant Recipients: Atropine should not be used for sinus bradycardia without reinnervation (2018 ACC/AHA/HRS: harm). The transplant team uses aminophylline or theophylline, a direct β-agonist or pacing.

• Scope: Critical-care transport (CCT), RN and Paramedic crews usually keep running an infusion the sending facility started. That varies by state and agency protocol.
• Storage & Stability: Current US labels for Isuprel and generics say 20–25°C (68–77°F), protected from light in the carton. Check yours. The label says to use diluted solution immediately, so follow the sending pharmacy's beyond-use date on any bag that travels.
• Carried Concentration: Mixes run from the label's 2 mcg/mL up to 10 times stronger, which is used when volume must be limited. Confirm the mcg/mL on the bag and in the pump library before you leave.
• Infusions in Transport: Give it a dedicated pump channel and line. Carry enough volume for the trip, since dilute mixes run at high mL/hr. Pads go on the patient and the pacer stays ready, because this is a bridge.
• Handoff Essentials: indication, current rate in mcg/min, concentration, last titration and heart-rate goal, rhythm and blood pressure response, pacing status, latest K⁺ and Mg²⁺, and magnesium given for torsades.

Mechanism of Action

• Synthetic catecholamine, nonselective β₁ and β₂ agonist. Its α affinity is very low.
• β₁ (heart): The sinus rate speeds up, AV conduction speeds up and contractility rises. Cardiac output goes up. The QT shortens.
• β₂ (vessels, airways): Skeletal muscle, renal and mesenteric beds dilate, and bronchial smooth muscle relaxes. SVR drops. Diastolic pressure falls, and mean pressure usually does too.
• Net effect: Rate and output rise. So does myocardial oxygen demand, while coronary perfusion pressure falls.

Pharmacokinetics

• Half-life: about 2 min (plasma).
• Metabolism: Catechol-O-methyltransferase (COMT) breaks it down in the liver and other tissues. It's a poor monoamine oxidase (MAO) substrate, with less neuronal uptake than epinephrine. The action runs slightly longer but stays brief.
• Elimination: dialyzability unknown.
• Tolerance: Continued use can build tolerance to the smooth-muscle effects.

Generic Name

Isoproterenol hydrochloride (international name: isoprenaline)

Brand Names

Isuprel; multiple generic vials

Pharmacologic Class

Synthetic catecholamine; nonselective β-adrenergic agonist

Therapeutic Class

Chronotrope and inotrope; bronchodilator (anesthesia)

Controlled Substance

Not controlled

ISMP High-Alert

Yes: ISMP high-alert medication (adrenergic agonists, IV; inotropic medications, IV)

Look-Alike / Sound-Alike

None on the ISMP confused drug names list