Nursing care
Adenosine: what to check before you give it
Written and reviewed by Dana Whitfield, RN, MSN · 4 min read · Updated September 2026
Short answer
Adenosine is given as a rapid IV push through a large vein, immediately followed by a saline flush, because its half-life is under ten seconds. A brief period of asystole or bradycardia after the push is expected, not a sign of harm, and the patient should be warned about it beforehand.
Mechanism, simply
Adenosine slows conduction through the AV node by activating A1 receptors, briefly blocking the re-entry circuit that sustains supraventricular tachycardia. It does this for seconds, not minutes, because it is taken up by red blood cells and metabolised almost as fast as it enters the bloodstream.
That short half-life is the whole point of the drug. It interrupts the arrhythmia just long enough for the sinus node to reassert control, then clears before it can cause any lasting effect on rhythm or blood pressure.
Indications you will see on the ward
Adenosine is first-line for terminating stable paroxysmal supraventricular tachycardia (PSVT) once vagal manoeuvres have failed. It is also used diagnostically: in a wide-complex or irregular tachycardia of uncertain origin, the brief AV block it produces can unmask the underlying atrial rhythm on the monitor.
It is not used for atrial fibrillation, atrial flutter, or ventricular tachycardia, and it will not convert those rhythms. Expect it ordered in the emergency department or on telemetry, with a defibrillator at the bedside as a precaution.
Assessment before administration
Confirm a working large-bore IV, ideally in the antecubital fossa, with continuous ECG and blood pressure monitoring already running. Ask about asthma or COPD, since adenosine can provoke bronchospasm, and check for second- or third-degree heart block or sick sinus syndrome without a pacemaker, both contraindications.
Have two syringes ready: one loaded with the adenosine dose, one with a 20 mL saline flush, connected via a three-way stopcock or two ports close to the insertion site. The push has to be pushed fast through a large vein with an immediate flush, because the half-life is under ten seconds — any delay between drug and flush lets it break down before it reaches the heart.
Toxicity and the antidote
There is no antidote, and none is needed. Because adenosine clears in seconds, adverse effects are self-limiting; the standard response to prolonged asystole or symptomatic bradycardia is supportive care and time, not a reversal agent.
If effects persist beyond what is expected, treat it as a separate clinical event rather than adenosine toxicity, and reassess the rhythm and the patient's haemodynamic status directly.
Interactions that matter
Dipyridamole blocks adenosine's cellular uptake and potentiates its effect substantially, so doses are typically reduced when a patient is on it. Theophylline and caffeine are adenosine receptor antagonists and can blunt or block the intended response, so ask about recent caffeine intake if the drug seems ineffective.
Carbamazepine has been associated with a higher degree of heart block after adenosine. None of these interactions change the administration technique, but they change what dose is ordered and what response to expect.
What the patient must be told
Warn the patient before you push the drug that they may feel a sense of impending doom, chest tightness, flushing, or a few seconds where it feels like their heart has stopped. This is expected and it passes within moments; saying so beforehand prevents panic during the brief asystole that follows.
Tell them the monitor will show a pause on purpose, and that staff are watching it closely. Once the rhythm settles, reassure them the sensation is over and unlikely to recur unless the arrhythmia returns.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our cardiovascular practice questions are the closest set to what this page covers.
Common questions
Why does adenosine have to be pushed so fast?
Because its half-life is under ten seconds, a slow push allows the drug to be metabolised before it reaches the AV node in an effective concentration. Fast administration through a large vein close to the heart, followed immediately by a flush, is what gets a therapeutic dose there intact.
Is the asystole after adenosine dangerous?
A brief pause of a few seconds is the expected pharmacological effect, not a complication. Staff monitor the rhythm continuously and the sinus node typically resumes on its own; a defibrillator is kept nearby as routine precaution rather than because it is usually needed.
Can adenosine be given through a peripheral line?
Yes, a large peripheral IV, most often in the antecubital fossa, is standard, provided the flush can be given immediately afterward. A central line is not required for adenosine, unlike some other cardiac drugs.
Why might a repeat dose of adenosine fail to work?
Recent caffeine or theophylline intake can antagonise adenosine's effect at the receptor level, and the arrhythmia may simply not be one adenosine terminates, such as atrial fibrillation or ventricular tachycardia. Reassess the rhythm strip before assuming a technique error.
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