Adenosine

Emergency & Prehospital

• Stable regular narrow-complex tachycardia (SVT): the first drug after vagal maneuvers. It converts AV nodal re-entrant (AVNRT) and AV re-entrant (AVRT) tachycardia, including AVRT in Wolff-Parkinson-White (WPW) syndrome.
• Stable wide-QRS tachycardia that is regular and monomorphic: it may be considered to treat the rhythm, or to clarify it when the cause is unclear. No conversion? Manage it as VT.
• Pediatric SVT: the first-line drug when IV/IO access is readily available. In the stable infant or child, vagal maneuvers come first.

ED / ICU / Transport

• Diagnostic AV block: it slows the ventricular rate so flutter waves or atrial fibrillation show. It does not convert them. Some focal atrial tachycardias terminate. Others only slow and keep going with AV block.
• Unstable regular narrow-complex SVT: it may be tried while synchronized cardioversion is prepared. It never delays the cardioversion.

Other Uses

• Pharmacologic stress imaging: a continuous infusion alongside myocardial perfusion imaging in patients who cannot exercise. Separate 20 mL and 30 mL vials.

2025 AHA/PALS sets the doses below. The FDA label is noted wherever it differs.

Available Forms

• Rapid-bolus vials (SVT): 3 mg/mL in 2 mL (6 mg) and 4 mL (12 mg) single-dose vials, preservative-free, in sodium chloride. EMS and transport carry this form.
• Stress-imaging vials (infusion only): 3 mg/mL in 20 mL (60 mg) and 30 mL (90 mg). Same concentration. Far larger total dose. Keep them out of resuscitation stock.

Adult Dosing

Pediatric Dosing

See weight-based dosing.

Preparation & Administration

• Dilution: No diluent. Give the 3 mg/mL solution undiluted.
• Push rate: rapid bolus over 1–2 seconds. A slow push gets metabolized before it reaches the heart.
• Flush: follow at once with a rapid NS flush, using two syringes on one port or a stopcock.
• Site: large proximal vein (antecubital). On a running line, inject at the port closest to the patient.
• IO: PALS 2025 recommends adenosine for pediatric SVT when IV or IO access is readily available. Push and flush it as you would for IV. Differs from FDA label: the label is IV only (peripheral bolus). Adults have no guideline or label IO dose. PALS 2025 endorses IO for pediatric SVT only.
• Before the push: strip recording, pads on, resuscitation equipment ready. Warn the patient about seconds of chest pressure, dyspnea and flushing.

Contraindications

• Second- or third-degree AV block without a functioning pacemaker
• Sinus node disease (sick sinus syndrome, symptomatic bradycardia) without a functioning pacemaker
• Known hypersensitivity to adenosine
• Asthma or active bronchospasm: contraindicated. Adenosine can cause severe bronchospasm in asthma (2025 AHA Part 9). Need rate control instead? IV diltiazem or verapamil is Class 2a for stable regular narrow-complex tachycardia. Unstable: synchronized cardioversion. Differs from FDA label: the bolus label says to avoid it in bronchospasm or asthma.
• Hemodynamically unstable, irregularly irregular (e.g., pre-excited AF) or polymorphic wide-QRS tachycardia: AHA 2025 Class 3: Harm (a guideline recommendation, not an FDA label contraindication)

Precautions

• Known WPW or accessory pathway: adenosine can trigger AF that conducts fast down the pathway. Have a defibrillator ready.
• Digoxin, with or without verapamil: VF after adenosine has been reported, but it is rare.
• COPD without bronchospasm: use caution. Stop for respiratory distress.

Hold / Reassess If

• High-grade AV block or a prolonged pause after a dose: give no further doses
• Wheeze or falling SpO₂: stop; treat bronchospasm
• Hypotension, altered mentation or shock with the tachycardia still present: synchronized cardioversion (if it follows conversion or a pause: supportive care/ACLS)
• Pause reveals flutter, AF or sinus tachycardia: stop; treat that rhythm
• No transient effect (no slowing, no flushing): fix the technique before escalating

Common

• Facial flushing (18%)
• Dyspnea (12%) and chest pressure (7%)
• Nausea (3%), headache (2%), lightheadedness (2%)
• Sense of dread or impending doom
• New rhythms at conversion in 55% (PACs, PVCs, brief AF, sinus bradycardia, AV block), usually lasting seconds

Serious / Life-Threatening

Overdose & Toxicity Management

• Course: The half-life is under 10 seconds. That is why most effects stop on their own within seconds (ESC 2019: about 20–30 s).
• Treat the effect: ACLS for asystole, block or VF. Bronchodilators for bronchospasm.
• Antagonist: Theophylline and aminophylline block adenosine receptors. The label says larger doses may be needed, or adenosine may not work, in their presence. No antagonist dose is listed here, so get poison center or specialist advice (pediatric dose not established). Not for adenosine-related seizures.

Clinically Significant Interactions

IV Compatibility

• Diluent: none; give undiluted, followed by an NS flush.
• Line: push alone at the port closest to the patient; do not mix with other drugs in the syringe.
• Verify with an institutional compatibility resource.

• Pediatrics: Used from the newborn period through adolescence. Controlled pediatric trials are lacking, though. PALS 2025 recommends it for SVT when IV or IO access is readily available. SVT that is unresponsive to vagal maneuvers and adenosine needs expert consultation. With cardiopulmonary compromise that persists despite vagal maneuvers, adenosine and synchronized cardioversion, and no expert available: IV procainamide, amiodarone or sotalol may be considered (PALS 2025, weak recommendation). See the Pediatric Dosing table.
• Neonates: Same per-kg doses. The label maximum is 0.3 mg/kg per dose, and never more than 12 mg. Involve pediatric cardiology early.
• Pregnancy: There are no animal or human studies. It is an endogenous nucleoside, so no fetal effects would be anticipated. The label still advises use only if clearly needed. ESC 2019: after vagal maneuvers, adenosine is the first-line drug in the second and third trimesters. First-trimester data are sparse. Use standard doses. Unstable: electrical cardioversion, then check the fetal heart rate.
• Lactation: Unknown whether it enters milk. A half-life under 10 seconds makes infant exposure unlikely.
• Older Adults: Higher risk of severe bradycardia or AV block, from nodal disease and interacting drugs. Same doses.
• Renal Impairment: Nothing to adjust. Adenosine does not depend on renal function.
• Hepatic Impairment: Nothing to adjust. Adenosine does not depend on hepatic function.
• Obesity / Dosing Weight: Adult doses are fixed. Children are dosed by actual weight, with adult caps. Anyone 50 kg or more gets adult doses.
• Heart Transplant Recipients: AHA 2025 warns that adenosine may have profound effects after heart transplant, and through a central line. 1 mg IV may be enough to end the tachycardia. Many protocols start at 3 mg, the traditional ACLS reduction. ESC 2019 takes a different view. It notes more recent evidence supporting adenosine in this group, with no particular cautions. Start with 1 mg, per the 2025 AHA text. Differs from FDA label: the label gives no reduced dose for transplant or central-line use.

• Scope: Paramedic, RN and critical-care transport per local protocol. It varies by state and agency protocol.
• Storage & Stability: 20–25°C (68–77°F). Never refrigerate it, because crystals can form. Warm crystallized vials to room temperature until clear. Never give a cloudy solution. Protect kits from vehicle cold.
• Carried Concentration: 3 mg/mL, 6 mg/2 mL and 12 mg/4 mL vials. Keep the 60 mg or 90 mg stress-imaging vials out of drug boxes.
• Technique in Transport: prepare both syringes first, use the most proximal port, and save strips before and after each dose.
• Handoff Essentials: pre-dose rhythm and 12-lead, time and dose of each push, response (conversion, unmasked rhythm, no effect), recurrence, and any vagal maneuvers or cardioversion.

Mechanism of Action

• A1 receptors in the SA and AV nodes: AV nodal conduction slows and the sinus node is depressed. That interrupts re-entry that uses the AV node, and SVT terminates.
• Transient AV block: The ventricular response slows in flutter and AF. That unmasks the atrial rhythm without converting it. Some focal atrial tachycardias terminate. Others continue with AV block.
• A2 receptors in vascular smooth muscle: vessels dilate, which causes flushing. A brief BP fall can come at higher or infused doses.
• Antagonists and potentiators: Methylxanthines compete at the receptor. Dipyridamole blocks cellular uptake. Atropine has no effect.

Pharmacokinetics

• Half-life: under 10 seconds in whole blood.
• Metabolism: it is cleared by uptake into red cells and vascular endothelium. Adenosine kinase phosphorylates it, or it is deaminated to inosine. No hepatic or renal step.
• Elimination: Inosine ends up as hypoxanthine, xanthine and uric acid.
• Efficacy: in US trials, 60% converted within a minute of 6 mg and 92% after 12 mg.

Generic Name

Adenosine (adenosine injection, USP)

Brand Names

Adenocard (SVT bolus) and Adenoscan (stress infusion) were the original brands; current US supply is generic

Pharmacologic Class

Endogenous purine nucleoside; adenosine receptor agonist

Therapeutic Class

Antiarrhythmic (AV nodal blocker); pharmacologic stress agent

Controlled Substance

Not controlled

ISMP High-Alert

Yes, by class: ISMP lists IV antiarrhythmics (examples given: lidocaine, amiodarone); adenosine is not named individually

Look-Alike / Sound-Alike

None commonly reported; do not confuse the 2 mL and 4 mL bolus vials with 20 mL and 30 mL stress-imaging vials