Understanding Adenosine (Adenocard)

So, recently, I was involved in a conversation, where the topic of Adenosine administration came up. It seems like there is a misunderstanding regarding its use and mechanism of action. Although this is not our classic ECG interpretation topic, I believe its worth talking about for a bit.

adenosine (1)

Adenosine, a Class V antiarrhythmic from the Vaughan Williams Classification, is an Endogenous Neucloside, meaning, already present in the body. In the EMS system, Adenosine is known for the treatment of Supraventricular Tachycardias (SVT), however, the reality is that, Adenosine is responsible for many actions in the body at a cellular level, depending on which receptor it binds to. During excessive reentry tachycardias (SVT), Adenosine, in simple terms, is given to slow down the overall ventricular rate.


  •  Adenosine binds to A1, one of multiple Adenosine receptors, which in the SA Node, it blocks L-type Calcium Channels and reduces Calcium influx, which may lead to a decreased firing rate, known as Negative Chronotropic Effect
  • Same channels at the AV Node, decrease conductivity , known as Negative Dromotropic Effect, down to the ventricles. This is what we want to do during tachyarrhythmias, especially with reentry capabilities, to slow down the ventricular rate

However, at higher or infused doses, such as during Cardiac Stress Test, Adenosine is given often as 60 mg over 4 minutes, not the typical administration for a reentry SVT right?

When infused slowly, Adenosine may bind to A2 receptors which in the heart and vasculature, can decrease Cyclic Adenosine Monophosphate (cAMP)

What is cAMP?

cAMP is a second messenger used to send signals from the cell membrane to intracellular areas to release chemicals like Calcium or break down proteins. Since Calcium is required for contraction and constriction, this leads to vasodilation. Physiologic changes in response to reduced blood pressure from vasodilation lead to increase heart rate to compensate for it. Understanding this details can help recognize complications that can happen when administrating Adenosine like AV blocks, short Asystole or other problems.

Other Adenosine receptors like Purinergic Receptors, for example, P1 receptors, lead to smooth muscle relaxation in the GI tracts.

Bottom line, Adenosine has many purposes in the body, therefore, it does not “die” or “dissapears” fast, but rather, it is used rapidly by the body, which is why it should be pushed fast, and as closed to the heart as possible, in order to reach the targeted areas during a reentry tachycardia, or “SVT”.


  • Joan says:

    Thanks for the great explanation!! Good stuff!

  • Erik says:

    Great explanation!

  • Sue Usry says:

    Have used this medication on patients many times with great results. I had success with the first dose of 6mg except twice and when the patient got to the ER it didn’t work for them either so they used 2 other medications that did.

  • Paul Peirce says:

    What I would like to know, is if you cannot get a Left AC, how effective is it to administer Adenosine via Humeral IO?
    I was told by tthe Medical Director that if it is your only option, just do it, but this still doesn’t address the question of proximity versus rate of absorption.

    • J edsell says:

      I would assume it would work pretty well. As long as you have good placement of the IO, the flow rate is definitely good enough. You can look up youtube videos of medications being given through the humeral head and testing its absorption rate. Everything i have seen it is on par with IVP.

  • Joppe says:

    Adenosine is also used to measure FFR in the cathlab to achieve maximum vasodilation in the vessels in the Heart.

  • Venkatesh says:

    Sir,adenosine is potassium channel opener ??

    • Ivan Rios says:

      BHello Venkatesh, Adenosine does not work on potassium channels. Adenosine recudes intracellular calcium by inhibiting cAMP.

  • Paul says:

    You don’t have to give adenosine through a line in the AC. While it is preferable to do so, I’ve given it through hand lines, and even a line or two more distal than that with fair success considering the locations of the lines. I would not advocate putting in an IO “just to give adenosine.”

  • Doug says:

    That is a great and concise explanation of adenosine – thank you very much! My question is about administration: if the issue surrounding the rapid administration of adenosine is that it is so rapidly metabolized, then it would seem to me that it is not ‘breaking down’ in the IV line but rather in the patient’s body; then is it truly that important whether I use an anticubital vein vs a hand vein? The distance between the two sites is likely less than 50 cm. If I’m rapidly infusing the drug with a bolus, does it really matter? In my experience, it has worked either way (when I cannot find a good AC vein). Thoughts?

    • Ivan Rios says:

      You could use the hand, and it can work. The only issue maybe unpredictable amount reaching the heart. But definitely can work through the hand.

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