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Bedside Snapshot
  • Core dose: 6 mg rapid IV push → 12 mg → 12 mg (if needed); reduce to 3 mg if given via central line
  • Onset/duration: Immediate onset (within seconds); half-life <10 seconds; effects last <1 minute
  • Key danger: Causes brief asystole (expected, 3–15 seconds); absolutely avoid in wide-complex tachycardia of unknown origin; can trigger severe bronchospasm in asthma/COPD
  • Special: Must give as rapid IV push over 1–3 seconds followed immediately by 20 mL saline flush; use large proximal vein (antecubital preferred); warn patient of flushing, chest pressure, and dyspnea; record continuous rhythm strip
Brand & Generic Names
  • Generic Name: Adenosine
  • Brand Names: Adenocard, Adenoscan
Medication Class

Antiarrhythmic (unclassified), endogenous nucleoside

Pharmacology

Mechanism of Action:

  • Slows conduction through the AV node by activating adenosine A1 receptors
  • Interrupts reentry pathways through the AV node, terminating supraventricular tachycardias (SVT)
  • Causes transient AV nodal block, allowing restoration of normal sinus rhythm
  • Does not affect atrial or ventricular tissue directly

Pharmacokinetics:

  • Onset: Immediate (within seconds)
  • Duration: Less than 10 seconds (half-life <10 sec)
  • Metabolism: Rapidly metabolized by adenosine deaminase in red blood cells and vascular endothelium
  • Elimination: Metabolites excreted renally
Indications
  • Primary indication: First-line treatment for stable, narrow-complex supraventricular tachycardia (SVT) in hemodynamically stable patients
  • Paroxysmal supraventricular tachycardia (PSVT)
  • AV nodal reentrant tachycardia (AVNRT)
  • AV reentrant tachycardia (AVRT) associated with Wolff-Parkinson-White (WPW) syndrome when narrow-complex
  • Diagnostic tool to differentiate SVT from ventricular tachycardia (VT) by temporarily slowing conduction
Conditions Treated
  • Supraventricular tachycardia (SVT)
  • Paroxysmal supraventricular tachycardia (PSVT)
  • AV nodal reentrant tachycardia (AVNRT)
  • AV reentrant tachycardia (AVRT)
  • Wolff-Parkinson-White syndrome (narrow-complex tachycardia only)
Dosing & Administration

Available Forms:

  • Injectable solution: 3 mg/mL in 2 mL and 4 mL vials (6 mg and 12 mg)

Dosing:

Patient Population Initial Dose Second Dose (if needed) Third Dose (if needed)
Adults 6 mg rapid IV push 12 mg rapid IV push 12 mg rapid IV push
Pediatrics 0.1 mg/kg (max 6 mg) rapid IV push 0.2 mg/kg (max 12 mg) rapid IV push 0.2 mg/kg (max 12 mg) rapid IV push
Administration Technique: Administer as rapid IV/IO push over 1-3 seconds followed immediately by 20 mL saline flush. Use large proximal vein (antecubital) for best results. Elevate arm after administration.
Contraindications

Absolute Contraindications:

  • Second- or third-degree AV block (unless patient has a functioning pacemaker)
  • Sick sinus syndrome (unless patient has a functioning pacemaker)
  • Known hypersensitivity to adenosine
  • Atrial fibrillation or atrial flutter with accessory pathway (e.g., WPW with wide-complex tachycardia)
  • Bronchospastic lung disease (e.g., asthma, COPD with active bronchospasm) - relative contraindication
Warning: Do not use adenosine for wide-complex tachycardia of uncertain origin. This may be ventricular tachycardia, and adenosine will not convert it. Use amiodarone or cardioversion instead.

Precautions:

  • Use with caution in patients on dipyridamole (Persantine) or carbamazepine - smaller doses may be needed
  • Patients on theophylline or caffeine may require higher doses
  • May cause transient severe bradycardia, asystole, or other dysrhythmias
Adverse Effects

Common (usually brief, lasting <1 minute):

  • Facial flushing (very common, almost universal)
  • Dyspnea or sense of chest tightness
  • Transient bradycardia or asystole (typically 3-5 seconds, can be up to 15 seconds)
  • Chest discomfort or pressure
  • Headache
  • Lightheadedness or dizziness
  • Nausea
  • Metallic taste

Serious (rare):

  • Prolonged asystole (rarely >15 seconds)
  • Ventricular fibrillation or ventricular tachycardia
  • Atrial fibrillation (transient)
  • Bronchospasm (especially in patients with asthma or COPD)
  • Severe hypotension
  • Seizures (very rare)
Patient Communication: Warn the patient before administration that they will feel flushing, chest pressure, and dyspnea for a few seconds. This significantly reduces anxiety.
Clinical Pearls
The "Push-Flush-Push" Technique: Adenosine has an extremely short half-life (<10 seconds). To maximize effectiveness, use the largest, most proximal IV site available (antecubital preferred). Push adenosine rapidly over 1-3 seconds, immediately follow with 20 mL saline flush pushed just as rapidly, and elevate the extremity. This ensures the medication reaches the heart before it's metabolized.
Expect Brief Asystole: Adenosine will often cause 3-15 seconds of asystole on the monitor. This is expected and therapeutic. Warn your patient, prepare your team, and have resuscitation equipment ready. The pause is what allows the sinus node to "reset" and restore normal rhythm.
Capture the Rhythm: Always print or record a continuous rhythm strip during adenosine administration. If the SVT doesn't convert, the brief pause may reveal underlying atrial activity (flutter waves, fibrillation) that can aid in diagnosis.
Drug Interactions: Theophylline and caffeine antagonize adenosine's effects (may need higher doses). Dipyridamole and carbamazepine potentiate adenosine's effects (use smaller doses, consider 3 mg initial dose).
Wide vs. Narrow: Adenosine is only indicated for narrow-complex tachycardias. If you have wide-complex tachycardia of uncertain origin, assume it's ventricular tachycardia and use amiodarone or cardioversion instead.
Success Rate: Adenosine successfully converts 90-95% of reentrant SVTs (AVNRT, AVRT). If it doesn't work after 3 doses, the rhythm is likely something else (atrial flutter, atrial fibrillation, or VT).
Asthma/COPD Caution: Use extreme caution or avoid in patients with active bronchospasm. Adenosine can trigger severe, life-threatening bronchospasm in asthmatics. If you must use it, have epinephrine and albuterol ready.
Central Line Dosing: If administered via central line, reduce initial dose to 3 mg for adults due to faster delivery to the heart.
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