Antiarrhythmic
Adenosine (Adenocard)
Also called Adenocard
Indications
- Conversion of regular narrow-complex SVT that runs through the AV node (AVNRT, AVRT) to sinus rhythm
- Unstable regular narrow-complex tachycardia while cardioversion is readied (ACLS)
- Stable, regular, monomorphic wide-complex tachycardia (ACLS; off-label)
- Diagnosis: brief AV block unmasks flutter waves or an atrial tachycardia (off-label)
- Pharmacologic stress for myocardial perfusion imaging (infusion product)
Dosing
| Where | Dose |
|---|---|
| Rhythm control | Adenosine: 6 mg rapid push with 20 mL flush, then 12 mg; use 3 mg through a central line or with dipyridamole or carbamazepine |
On the quick cards
Mechanism of action
Adenosine, an endogenous purine nucleoside, binds Gi-coupled A1 receptors in the SA node, AV node and atria. The freed βγ subunits open the GIRK potassium channel (IKAdo, the same channel acetylcholine opens), hyperpolarizing nodal cells, while adenylyl cyclase inhibition lowers cAMP and with it ICaL and If. A few seconds of AV-node block follow, breaking reentry circuits that run through the node. Older lists leave it outside the Vaughan Williams classes; the modernized scheme (Lei 2018) puts it in class II as a G-protein signaling modulator.
Pharmacology
- Cardiovascular (A1): seconds of sinus slowing and AV block, often a pause or brief asystole; shorter atrial refractoriness can trigger AF
- Cardiovascular (A2A): coronary and systemic vasodilation, the basis of stress imaging; flushing in 18% (label)
- Respiratory: dyspnea in 12% (label); bronchospasm in asthma through A2B and A3 receptors
- Diagnostic: ends AV-nodal reentry but only briefly slows the ventricular rate in flutter, AF or atrial tachycardia
- Other: chest pressure (7%) and a sense of doom; effects fade within about a minute
Pharmacokinetics
| Onset | Seconds; most responders convert within 1 min (label) |
|---|---|
| Duration | Under 1–2 min, so SVT can recur |
| Half-life | Under 10 s in whole blood (label) |
| Distribution | Taken up within seconds by red cells and endothelium through nucleoside transporters, which dipyridamole blocks |
| Metabolism | Adenosine kinase to AMP, or adenosine deaminase to inosine and on to uric acid (label) |
| Elimination | No liver or kidney role, so unchanged in hepatic or renal failure (label) |
| Routes | IV push over 1–2 s into a large proximal vein with an immediate saline flush; IO in children |
Chemistry
- A purine nucleoside (C₁₀H₁₃N₅O₄, MW 267.24): adenine joined to D-ribose by a β-N9 glycosidic bond, identical to the body's own adenosine
- A single natural stereoisomer; water soluble and uncharged at pH 7.4 (pKa 3.6 and 12.4, PubChem), so it enters cells through transporters, not by diffusion
- Supplied as 3 mg/mL in 0.9% NaCl without preservative, pH 4.5–7.5 (label)
- Do not refrigerate: it crystallizes, and warming to room temperature redissolves the crystals (label)
Adverse effects and cautions
In the one-pagers
- Rhythm GallerySinus, atrial and junctional: SVT: regular, narrow, fast (here about 180), P waves hidden. Stable: vagal maneuver, then adenosine 6 mg rapid push and flush, then 12 mg. Unstable: synchronized cardioversion.
- ACLS Algorithms in BriefTachycardia with a pulse: Usually 150/min or more. Unstable because of the rhythm (not, say, sepsis)? Synchronized cardioversion, sedated when feasible; if regular and narrow, adenosine may be tried while preparing.
- Pediatric Assessment and EmergenciesPALS: arrest, bradycardia, tachycardia and IO access: Adenosine (SVT): 0.1 mg/kg rapid (max 6 mg), then 0.2 mg/kg (max 12 mg)
- ED Triage and ESIDecision point A: lifesaving intervention now: Medications: Naloxone, dextrose, epinephrine, atropine, adenosine, dopamine: Aspirin, IV nitroglycerin, antibiotics, heparin, analgesics
- Heart FailureAdvanced HF: shock bridge, MCS, transplant and palliative care: A peak VO₂ ≤12 mL/kg/min on a β-blocker supports transplant listing (ISHLT 2016), and median survival after transplant is about 12.5 years (ISHLT registry, 2002–2009 era). The denervated heart rests at 90–110 bpm, does not respond to atropine (use isoproterenol, epinephrine or pacing), needs a reduced adenosine dose, and develops allo
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In the algorithms
Other antiarrhythmic drugs
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Sources
- FDA label: Adenosine injection (2024)
- FDA label: Adenosine for perfusion imaging, Mylan (2022)
- Lei 2018, 2025 update (classification)
- PubChem: adenosine
For education and exam preparation only. Follow your institution’s protocols. Typical adult values for study. Follow the order, the label and your institution's protocols.