Adenosine: Effect in Supraventricular Tachycardia
Adenosine is an endogenous purine nucleoside used in emergency medicine and cardiology as a highly effective antiarrhythmic agent (brand names Adrekar, Adenoscan, and generics). In Germany, adenosine is the first-line agent for acute conversion of paroxysmal supraventricular tachycardias. It is also used as a pharmacological stress test in nuclear medicine stress myocardial perfusion imaging when physical exertion is not possible.
Characteristic of adenosine is its extremely short duration of action. The half-life is only a few seconds because the substance is rapidly taken up by erythrocytes and endothelial cells and enzymatically degraded. This property is clinically a major advantage because unwanted effects disappear quickly, yet the application requires careful preparation with defibrillation readiness, resuscitation team, and continuous ECG monitoring. Adenosine is not suitable for self-administration or outpatient oral therapy.
Mechanism of Action
Adenosine binds primarily to A1 receptors in the atrium and AV node. Activation of these Gi coupled receptors leads to hyperpolarisation of the cell membrane through opening of potassium channels and inhibition of adenylyl cyclase. In the AV node, this results in a short-term blockade of impulse conduction lasting several seconds. Reentry tachycardias that traverse the AV node (for example, AV nodal reentry tachycardia and AV reentry tachycardia in accessory pathway), are interrupted this way.
At A2A receptors of the vessel wall, adenosine acts as a vasodilator, explaining the effect in myocardial perfusion testing. During adenosine infusion, healthy coronary arteries dilate significantly, while stenotic areas respond limitedly, allowing comparison between perfused and underperfused areas. In the central nervous system, adenosine has an inhibitory effect on neuronal activity, which is antagonised by caffeine and theophylline.
Adenosine is converted within cells by adenosine deaminase to inosine and by adenosine kinase to AMP. The effective half-life is less than ten seconds, which is why the substance must be administered as a rapid bolus through a three-way stopcock near the heart and immediately flushed with saline.
Applications
- Acute supraventricular tachycardia including AV nodal reentry tachycardia and AV reentry tachycardia for diagnostic unmasking and conversion
- Differential diagnostic support in tachycardias with wide QRS complex, because adenosine provides clues about underlying mechanisms through brief AV blockade
- Pharmacological stress myocardial perfusion imaging or stress MRI when physical exertion is not possible
- Diagnostic tests in suspected accessory pathways or specific supraventricular tachycardia mechanisms
Adenosine is not suitable for rate control in atrial fibrillation or conversion of unstable ventricular tachyarrhythmia. In haemodynamically unstable tachycardias, electrical cardioversion is the treatment of choice. In Wolff Parkinson White syndrome with atrial fibrillation, adenosine is dangerous because it can paradoxically increase ventricular rate.
Dosage and Administration
Standard dose adults: 6 mg as a rapid intravenous bolus over 1 to 2 seconds, preferably through a large-bore access near the heart, followed by 10 ml saline flush.
If no conversion after 1 to 2 minutes: 12 mg bolus, if necessary repeated after a further 1 to 2 minutes with 12 mg.
Paediatric: 0.1 mg per kg body weight as bolus, if necessary increase to 0.2 mg per kg, maximum 12 mg per single dose.
Pharmacological stress test: Infusion at 140 µg per kg per minute over six minutes under ECG monitoring. Variant protocol with shortened infusion possible.
Administration: Continuous ECG, blood pressure, pulse oximetry, immediate defibrillation readiness. Patient counselling regarding typical, often unpleasant symptoms such as chest pressure, warmth sensation, brief dyspnoea. These effects are desired and part of the mechanism of action, usually resolving within seconds.
Renal insufficiency and hepatic insufficiency: No dose adjustment required because adenosine is metabolised within cells.
Side Effects
Very common (short-term): Chest pressure, warmth sensation, flushing, brief dyspnoea, dizziness, transient AV blockade with asystole for a few seconds, headache.
Common: Nausea, transient hypotension, conduction disturbances, atrial or ventricular ectopic beats.
Occasional to rare: Bronchospasm, especially in asthma or COPD, prolonged AV blockade, sinus node dysfunction, new atrial fibrillation episodes, very rarely sustained bradycardia or asystole.
In patients with Wolff Parkinson White syndrome and atrial fibrillation: Adenosine can favour conduction over the accessory pathway and lead to rapid ventricular rates with risk of ventricular fibrillation. Adenosine is contraindicated here.
In patients with asthma: Bronchospasm possible, therefore caution and readiness with bronchodilators.
Interactions
- Caffeine and theophylline: Antagonists at adenosine receptors, significantly reduced effect. Before pharmacological stress tests, patients should avoid caffeine for 24 hours and theophylline for 12 to 24 hours.
- Dipyridamole: Inhibits cellular uptake of adenosine and significantly enhances its effect. Bolus doses must be reduced or the substance cannot be used at all.
- Carbamazepine: Can prolong AV blockade under adenosine, higher caution.
- Digoxin and verapamil: Theoretically additive bradycardia and AV blockade, clinically rarely relevant with short adenosine effect.
- Beta blockers and calcium antagonists: No direct pharmacological interaction, but concomitant medication can influence sinus node and AV node function.
- Sublingual tablets or inhalants with sympathomimetics: No direct interaction, clinical observation advisable.
Special Notes
Pregnancy: Adenosine can be used in vital supraventricular tachycardia, ideally in hospital setting. Breastfeeding: Not clinically relevant due to very short half-life.
Children: Established in paediatric emergency medicine.
Before use: Continuous ECG, intravenous access, defibrillator and emergency equipment ready, patient counselling about short-term symptoms.
Before pharmacological stress tests: Abstinence from caffeine, theophylline, dipyridamole according to protocol, ask about asthma history, consider appropriate alternative stress (dobutamine) in asthma.
Vagal manoeuvres before adenosine: In stable supraventricular tachycardia, carotid sinus massage or Valsalva manoeuvre are first options, often successful and without medication. If these fail, adenosine is the next choice.
Patient communication: Patients should know that the short duration of action is sometimes very unpleasant (chest pressure, dizziness, dyspnoea), but passes within seconds. This counselling reduces anxiety and stress.
Driving fitness: Not affected by acute use, restored after brief observation period.
You might also be interested in
- Verapamil, Calcium antagonist in supraventricular tachycardia
- Diltiazem, another rate control option
- Amiodarone, broad-spectrum antiarrhythmic
- Propranolol, Beta blocker in cardiac indications
- Noradrenaline, Vasopressor in acute medicine
Frequently Asked Questions
Why is adenosine so short-acting?
Adenosine is rapidly degraded within cells by adenosine deaminase and adenosine kinase, the half-life is less than ten seconds. This is clinically advantageous because unwanted effects disappear quickly. At the same time, the short duration of action requires very rapid bolus administration directly at the heart.
Why can't I drink coffee before a stress test?
Caffeine blocks adenosine receptors and reduces the effect of the test. Abstinence of 24 hours before pharmacological stress myocardial perfusion imaging is therefore standard, as is avoidance of theophylline-containing medications. Patients usually receive written instructions.
Is asystole after adenosine dangerous?
Brief asystole lasting a few seconds is part of the mechanism of action and generally harmless. It ends by itself as soon as the active substance is metabolised. In very rare cases, prolonged bradycardia can occur, which is why defibrillation and emergency team are on standby.
What to do if bronchospasm occurs with adenosine?
Adenosine can trigger bronchospasm in asthma. Before use, a history of asthma is obtained. When dyspnoea occurs, a beta 2 agonist such as salbutamol is kept ready. The effect is usually short-lived because adenosine is rapidly metabolised.
Sources
- Gelbe Liste, Adenosine Active Ingredient Profile
- BfArM, Federal Institute for Drugs and Medical Devices
- AWMF, Guidelines on Supraventricular Tachycardia
- European Society of Cardiology, Cardiology Guidelines
Legal Notice and Disclaimer
The information provided on this page is for general information purposes only and does not constitute medical advice, diagnosis or treatment recommendation. It does not replace the advice of a licensed physician or pharmacist. The use of adenosine is exclusively by trained medical personnel in appropriate settings with emergency equipment. All information is based on published specialist information and recognised scientific sources at the time of creation, the current specialist information from the manufacturer always taking precedence. Sanoliste assumes no liability for completeness, timeliness or accuracy of the information presented. In case of medical emergency, call emergency number 112.