Focus on Pharm: Adenosine

Adenosine is one of the scariest, and most amazing, drugs I’ve ever administered as a nurse. In this article, you’ll learn the key things to know using the Straight A Nursing DRRUGS framework.

D: Drug Class

Adenosine is in the therapeutic class of Class V antiarrhythmics, which is a miscellaneous group of antiarrhythmics that don’t fit in with a traditional class. To refresh your memory:

• Class I: sodium channel blockers
• Class II: beta blockers
• Class III: potassium channel blockers
• Class IV: calcium channel blockers
• Class V: miscellaneous antiarrhythmics including adenosine and digoxin

Adenosine has a very rapid onset of action and a very short half life of only 10 seconds.

R: Routes of administration

Adenosine is available as an IV medication only. It is given as a rapid IV push because it’s half life is so short…only about ten seconds.

When given as a rapid IV push, adenosine causes asystole for about 7 seconds before conduction resumes. 

R: Regular dose range

When following standard guidelines, such as those outlined in ACLS, adenosine is given as 6 mg for the first dose and, if needed, followed up by a second dose of 12 mg 1 to 2 minutes later. If still ineffective, a third and final dose of 12 mg may be given. 

Smaller doses of 3 mg for the initial dose and 6 mg for subsequent doses may be utilized in some cases. If the adult patient is the recipient of a cardiac transplant the denervated post transplant heart has an AV node that is 3 to 5 times more sensitive to adenosine, necessitating a lower dose. 

Additionally, studies show that because a central line gets the medication into circulation much faster, smaller doses are currently recommended and the standard dose can cause prolonged bradycardia and more severe side effects.

A lower dose may also be utilized for patients taking carbamazepine or dipyridamole. Concurrent use with the anticonvulsant medication carbamazepine can increase the risk of the patient going into a progressive heart block. Concurrent use with dipyridamole (an antiplatelet agent and vasodilator), increases the effects of adenosine.

When administered to induce stress in a cardiac stress test, adenosine is weight based and given as a steady infusion for six minutes instead of given as a rapid IV push.

U: Uses of Adenosine

Adenosine is utilized as both a diagnostic agent and as a therapeutic one. Therapeutically, it is used to treat supraventricular tachycardia (SVT), which is a very fast narrow complex rhythm above 150 bpm. 

Adenosine exerts its action via purinergic adenosine receptors, which are located throughout the body, including the tissue of the cardiac AV node. Adenosine acts on receptors in the AV node which significantly slows cardiac conduction. It does this by driving potassium out of the cell, and inhibiting the influx of calcium into the cell. This disrupts the resting membrane potential of the cell and leads to a longer time needed for depolarization and slower conduction, bringing the patient out of SVT.

Adenosine may also be utilized diagnostically. Because narrow complex tachycardias are difficult to analyze due to the high rate, adenosine may be used to slow the heart rate enough that the underlying arrhythmia can be identified. 

Another very common diagnostic use of adenosine is in a cardiac stress test which evaluates myocardial perfusion in individuals with coronary artery disease. Some patients will run on a treadmill to induce cardiac stress, while others will require pharmacologically induced stress. In addition to its ability to slow conduction at the AV node, adenosine also causes vasodilation. When given in a cardiac stress test, adenosine causes stress on the heart by dilating the vessels leading to something called “coronary steal.” In coronary steal, blood flow is essentially “stolen” from more narrow arteries in the heart and diverted to other blood vessels, which further intensifies ischemia from those areas of the heart.

An off-label use for adenosine is to aid in the clipping of cerebral aneurysms. The brief period of asystole and hypotension that occur with adenosine administration decompresses the aneurysm sac making it easier for the surgeon to visualize and treat.

This study discusses the use of inhaled adenosine to reduce inflammation and the onset of cytokin storm in COVID-19 patients. The study in question showed a six-day reduction in length of stay.

G: Guidelines

Administration – If adenosine is refrigerated or cold, it may have crystals which dissolve once the medication is at room temperature (only clear solution should be administered). When given for SVT, adenosine is given as a rapid IV push over 1-2 seconds via a peripheral IV (choose one that’s closest to the trunk if you have multiple options). Flush with a rapid bolus of 20 ml saline to ensure the medication reaches systemic circulation quickly. If given too slowly, the effect could be vasodilation with increased heart rate.

When given for diagnostic testing with a cardiac stress test, the medication is given as a weight-based infusion over 6 minutes.

Safety considerations – Adenosine is contraindicated in 2nd or 3rd degree AV block and sick sinus syndrome (unless the patient has a pacemaker in place). It should also be avoided in myocardial ischemia and infarction unless being used as a diagnostic tool. It is also not to be used in those who are breastfeeding and should be used cautiously in pregnancy as its safety is not established. Because adenosine can cause bronchospasm in some patients, it is used cautiously or not at all in individuals with asthma or COPD. And, as with all medications, it is avoided in patients who have a hypersensitivity reaction.

Adenosine is not utilized for atrial fibrillation, atrial flutter or ventricular tachycardia. In fact, using adenosine with a polymorphic or irregular wide-complex tachycardia can cause ventricular fibrillation and cardiac arrest. And in cases of a wide complex tachycardia where the underlying rhythm is atrial fibrillation, using adenosine can cause cardiac arrest.

If the patient receiving adenosine has Wolf-Parkinson-White syndrome, it is recommended that a defibrillator be at the bedside in cases of rapid deterioration. 

Because adenosine can cause significant hypotension, the risk for this is higher in patients who have hypovolemia, valve stenosis, pericardial effusion, pericarditis and autonomic neuropathy.

Assessment – All patients receiving adenosine will be on continuous cardiac monitoring. Watch for transient arrhythmias after the initial period of asystole. These usually only last a few seconds and typically include PVCs, PACs, sinus bradycardia, skipped beats, heart blocks and sinus tachycardia. It is also standard practice to measure blood pressure before, during and after therapy. Monitor respiratory status as well and note that adenosine can cause bronchospasm in patients with a history of asthma.

Drug-drug interactions – In addition to carbamazepine and dipyridamole as mentioned above, adenosine interacts with theophylline, caffeine and digoxin. Its effects are decreased by theophylline and caffeine, while concurrent use with digoxin increases the risk for ventricular fibrillation.

S: Side Effects of Adenosine

Some adverse effects of adenosine are typically short-lived due to the medications very short duration of action. These include nausea, sweating, nervousness, flushing, lightheadedness and even a feeling of impending doom. I’ve heard patients state they feel like they’ve been kicked in the chest.

Note that adenosine can cause more serious cardiac-related effects such as onset of a new cardiac arrhythmia including AV block, atrial fibrillation, ventricular tachycardia, prolonged asystole, cardiac ischemia and premature contractions.

The most common adverse effects are arrhythmia, facial flushing and shortness of breath.

I hope this quick overview of adenosine helps you understand it better. For more pharmacology lessons, click here.

You can review adenosine again on the go in episode 271 of the Straight A Nursing podcast. Tune in wherever you get your podcast fix, or straight from the website here.

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REFERENCES:

Caracciolo, M., Correale, P., Mangano, C., Foti, G., Falcone, C., Macheda, S., Cuzzola, M., Conte, M., Falzea, A. C., Iuliano, E., Morabito, A., Caraglia, M., Polimeni, N., Ferrarelli, A., Labate, D., Tescione, M., Di Renzo, L., Chiricolo, G., Romano, L., & De Lorenzo, A. (2021). Efficacy and Effect of Inhaled Adenosine Treatment in Hospitalized COVID-19 Patients. Frontiers in Immunology, 12. https://www.frontiersin.org/articles/10.3389/fimmu.2021.613070

Davis’s Drug Gide. (n.d.). Adenosine (Adenocard, Adenoscan). https://www.drugguide.com/ddo/view/Davis-Drug-Guide/51015/all/adenosine?refer=true

Desai, V. R., Rosas, A. L., & Britz, G. W. (2017). Adenosine to facilitate the clipping of cerebral aneurysms: Literature review. Stroke and Vascular Neurology, 2(4), 204–209. https://doi.org/10.1136/svn-2017-000082

King, G. S., Goyal, A., Grigorova, Y., & Hashmi, M. F. (2022). Antiarrhythmic Medications. In StatPearls. StatPearls Publishing. http://www.ncbi.nlm.nih.gov/books/NBK482322/

Kohli, P. (n.d.). Coronary Steal Syndrome: Causes, Symptoms, Treatment. https://www.healthline.com/health/heart/all-about-coronary-steal-syndrome

Singh, S., & McKintosh, R. (2022). Adenosine. In StatPearls. StatPearls Publishing. http://www.ncbi.nlm.nih.gov/books/NBK519049/

University of Maryland. (n.d.). UMEM Educational Pearls. https://umem.org/educational_pearls/1523/