Adenosin Macure: Uses, Dosage & Side Effects
An endogenous nucleoside antiarrhythmic agent used for the rapid conversion of paroxysmal supraventricular tachycardia (SVT) to normal sinus rhythm
Adenosin Macure (adenosine 5 mg/ml) is an injectable antiarrhythmic medication used primarily in emergency and hospital settings for the rapid termination of paroxysmal supraventricular tachycardia (PSVT). Adenosine is an endogenous nucleoside – a substance naturally produced in every cell of the body – that exerts powerful effects on the heart's electrical conduction system. When administered as a rapid intravenous bolus, it temporarily slows or blocks conduction through the atrioventricular (AV) node, interrupting the re-entrant circuits responsible for most forms of SVT. With an ultra-short half-life of less than 10 seconds, adenosine's effects are brief and self-limiting, making it remarkably safe when used under appropriate medical supervision with continuous ECG monitoring.
Quick Facts: Adenosin Macure
Key Takeaways
- Adenosin Macure contains adenosine, a naturally occurring nucleoside that acts on the AV node to rapidly terminate paroxysmal supraventricular tachycardia (PSVT), typically within 10–30 seconds of administration.
- It must be given as a rapid intravenous bolus (over 1–2 seconds) followed by a saline flush, under continuous ECG monitoring in a healthcare setting equipped for cardiac resuscitation.
- The ultra-short half-life of less than 10 seconds means side effects (facial flushing, chest discomfort, dyspnea) are almost always transient and resolve within 1–2 minutes.
- Caffeine and theophylline are competitive antagonists at adenosine receptors and can reduce or abolish its effect; dipyridamole markedly potentiates adenosine and requires significant dose reduction.
- Adenosine is contraindicated in patients with second- or third-degree AV block (without pacemaker), sick sinus syndrome, long QT syndrome, severe hypotension, decompensated heart failure, and severe asthma or COPD due to bronchospasm risk.
What Is Adenosin Macure and What Is It Used For?
Adenosin Macure contains adenosine, an endogenous purine nucleoside that plays fundamental roles throughout the human body. In every cell, adenosine is produced as a metabolic byproduct of adenosine triphosphate (ATP) breakdown and participates in numerous physiological processes, including energy metabolism, signal transduction, and neurotransmission. However, it is adenosine's specific effects on the heart's electrical conduction system that make it invaluable as a pharmacological agent in cardiology and emergency medicine.
The primary therapeutic application of Adenosin Macure is the rapid termination of paroxysmal supraventricular tachycardia (PSVT). PSVT is a group of arrhythmias characterized by episodes of abnormally fast heart rate (typically 150–250 beats per minute) that originate above the ventricles. The most common forms of PSVT are atrioventricular nodal re-entrant tachycardia (AVNRT) and atrioventricular re-entrant tachycardia (AVRT), including tachycardias associated with accessory pathways such as those seen in Wolff-Parkinson-White (WPW) syndrome. Both AVNRT and AVRT depend on the AV node as a critical limb of their re-entrant circuit, making them susceptible to termination by adenosine.
When adenosine is administered as a rapid intravenous bolus, it binds to specific adenosine A1 receptors located on the cell membranes of AV nodal myocytes. Activation of these receptors triggers a cascade of intracellular events: the G-protein-coupled receptor activates an inward rectifier potassium channel (IKAdo), causing potassium efflux and membrane hyperpolarization. Simultaneously, adenosine inhibits the slow inward calcium current (ICa,L) through L-type calcium channels and reduces the hyperpolarization-activated pacemaker current (If). The combined effect of increased potassium conductance and decreased calcium conductance profoundly slows conduction velocity and increases the refractory period of the AV node. This transient AV block interrupts the re-entrant circuit that sustains PSVT, allowing the heart to reset to normal sinus rhythm.
Beyond its primary antiarrhythmic application, Adenosin Macure is used in several other clinical scenarios. In the diagnostic evaluation of tachyarrhythmias, adenosine is administered to patients presenting with regular narrow-complex or broad-complex tachycardias of uncertain mechanism. By transiently blocking AV conduction, adenosine can unmask the underlying atrial activity (such as flutter waves in atrial flutter or P-waves in atrial tachycardia), helping clinicians identify the precise arrhythmia mechanism. This diagnostic use is particularly valuable in the emergency department where rapid differentiation of arrhythmia types guides treatment decisions.
Adenosine is also widely used in pharmacological myocardial perfusion imaging (cardiac stress testing) through its vasodilatory properties. When infused at a controlled rate (typically 140 micrograms/kg/min over 6 minutes), adenosine acts on A2A receptors in coronary arteries to produce coronary vasodilatation. Normal coronary arteries dilate significantly, increasing blood flow, while stenotic arteries cannot dilate proportionally. This differential flow response creates a detectable perfusion defect on imaging (such as single-photon emission computed tomography, SPECT, or positron emission tomography, PET), allowing non-invasive identification of coronary artery disease. However, this cardiac stress testing use requires a different administration protocol and dose than the antiarrhythmic use.
Adenosine must be injected as a rapid intravenous bolus (over 1–2 seconds) as close to the heart as possible, immediately followed by a rapid saline flush. This is because adenosine has an extraordinarily short half-life of less than 10 seconds – it is rapidly taken up by red blood cells and vascular endothelial cells and deaminated to inosine by the enzyme adenosine deaminase. If injected too slowly, the drug is metabolized before reaching the heart in sufficient concentration to produce AV nodal block.
What Should You Know Before Receiving Adenosin Macure?
Contraindications
There are absolute clinical situations in which Adenosin Macure must not be used. Understanding these contraindications is critical because adenosine is typically administered in acute, time-pressured settings where rapid decision-making is essential.
- Second- or third-degree AV block: Adenosine works by transiently blocking AV conduction. In patients who already have significant AV conduction disease (without a functioning pacemaker), adenosine can cause prolonged, potentially dangerous AV block or asystole.
- Sick sinus syndrome: Patients with sinus node dysfunction may experience prolonged sinus arrest or severe bradycardia after adenosine, unless a functional pacemaker is in place.
- Long QT syndrome: Adenosine can prolong the QT interval and may trigger polymorphic ventricular tachycardia (torsades de pointes) in patients with congenital or acquired long QT syndrome.
- Severe asthma or COPD: Adenosine can cause life-threatening bronchospasm by activating adenosine A2B receptors on bronchial smooth muscle and stimulating mast cell mediator release. It should be avoided in patients with asthma, severe COPD, or a history of bronchospastic lung disease.
- Severe hypotension: Adenosine causes vasodilation and can further lower blood pressure. In patients with systolic blood pressure below 90 mmHg, it may precipitate cardiovascular collapse.
- Decompensated heart failure: In patients with severe, decompensated heart failure, adenosine's negative chronotropic and dromotropic effects can further compromise cardiac output.
- Hypersensitivity: Do not use in patients with known allergy to adenosine or any excipient in the formulation.
Warnings and Precautions
Adenosine must only be administered in a setting where continuous electrocardiographic (ECG) monitoring is available and full resuscitation equipment is immediately accessible. Transient arrhythmias – including brief asystole, AV block, atrial fibrillation, and ventricular ectopy – commonly occur during and immediately after administration. While these are usually self-limiting, healthcare professionals must be prepared to intervene if prolonged or hemodynamically significant arrhythmias develop.
Before and during treatment with Adenosin Macure, the following precautions should be observed:
- Atrial fibrillation/flutter with accessory pathways: In patients with known or suspected pre-excitation syndromes (e.g., WPW syndrome) who present with atrial fibrillation or flutter, adenosine should be used with extreme caution. While adenosine is safe for terminating orthodromic AVRT in WPW, transient AV block can paradoxically enhance conduction through the accessory pathway in atrial fibrillation, potentially accelerating the ventricular rate to dangerous levels.
- Heart transplant recipients: Patients who have undergone cardiac transplantation may exhibit enhanced sensitivity to adenosine due to denervation supersensitivity. Significantly reduced doses should be used, and the initial dose should be no more than 3 mg (1 mg in some protocols).
- Unstable angina or recent myocardial infarction: Adenosine's vasodilatory effects can alter coronary blood flow distribution (coronary steal phenomenon) and should be used cautiously in patients with active ischemia.
- Autonomic neuropathy: Patients with autonomic dysfunction may have an exaggerated hemodynamic response to adenosine.
- Seizure disorders: Rare cases of seizure activity have been reported in association with adenosine administration, particularly in patients with a history of epilepsy.
- Stenotic valvular heart disease: In patients with significant aortic or mitral stenosis, adenosine-induced hypotension may be poorly tolerated.
- Pericarditis or pericardial effusion: These conditions can be associated with atrial arrhythmias, and adenosine may not be the most appropriate first-line treatment.
Pregnancy and Breastfeeding
Adenosine is generally considered one of the safer antiarrhythmic options during pregnancy for the acute management of SVT. Professional guidelines from the American Heart Association (AHA), the European Society of Cardiology (ESC), and the Heart Rhythm Society (HRS) include adenosine as a recommended first-line pharmacological option for SVT in pregnant women when vagal maneuvers have failed.
The rationale for this favorable safety profile lies in adenosine's pharmacokinetic characteristics. Its ultra-short half-life of less than 10 seconds means that the drug is almost entirely metabolized before it can cross the placenta in significant amounts. There are no controlled human studies of adenosine in pregnancy, but extensive clinical experience and case series spanning several decades have not demonstrated adverse fetal effects. Animal reproductive toxicity studies are not available for adenosine specifically, as it is an endogenous substance present in all mammalian tissues.
Despite this relatively reassuring profile, adenosine should still only be administered in pregnancy when clinically indicated and in a monitored setting with resuscitation capabilities. The potential risks of untreated sustained SVT to both mother and fetus (including hemodynamic compromise, fetal hypoperfusion, and preterm labour) typically outweigh the minimal risk of appropriately administered adenosine.
Adenosine is a naturally occurring substance and is not expected to accumulate in breast milk in pharmacologically significant amounts given its rapid metabolism. No specific restrictions on breastfeeding following adenosine administration have been recommended by major guidelines.
Driving and Operating Machinery
Adenosin Macure is administered exclusively in hospital or emergency settings. It is not a medication that patients self-administer. Following treatment for SVT, patients should be monitored until clinically stable. Transient lightheadedness, dizziness, or blurred vision may occur after administration, and patients should not drive or operate machinery until these symptoms have fully resolved and their physician has confirmed it is safe to do so.
How Does Adenosin Macure Interact with Other Drugs?
The drug interactions of adenosine are clinically very important because they directly affect the dose required and the safety of administration. Adenosine exerts its antiarrhythmic effect by binding to specific cell-surface receptors (primarily A1 subtype on the AV node), and many common substances can either block or enhance this interaction. A thorough medication and dietary history should be obtained before adenosine is given.
Major Interactions
| Interacting Drug | Effect | Clinical Significance |
|---|---|---|
| Dipyridamole | Blocks cellular uptake of adenosine, markedly increasing and prolonging its effect (up to 4-fold potentiation) | Reduce adenosine dose by at least 75%. Use extreme caution; start with 0.5–1 mg initial dose |
| Caffeine (coffee, tea, energy drinks, chocolate) | Competitive antagonist at adenosine A1 and A2A receptors; blocks the therapeutic effect | May need higher doses; consider alternative treatment in heavy caffeine users |
| Theophylline / Aminophylline | Competitive antagonist at adenosine receptors; abolishes or markedly reduces effect | Adenosine likely ineffective; use alternative antiarrhythmic (e.g., verapamil if appropriate) |
| Carbamazepine | Potentiates adenosine's AV nodal blocking effect; increased risk of prolonged AV block | Use lower initial dose; increased risk of prolonged high-degree AV block |
Minor Interactions
| Interacting Drug | Effect | Clinical Significance |
|---|---|---|
| Verapamil / Diltiazem | Additive AV nodal depression; combined negative dromotropic effect | Use cautiously; increased risk of bradycardia and hypotension |
| Beta-blockers (atenolol, metoprolol, propranolol) | Additive AV nodal blocking and negative chronotropic effects | Monitor closely; may enhance adenosine's bradycardic effect |
| Digoxin | Additive depression of AV node conduction | Use with caution; combined effect may prolong AV block |
| Nicotine (smoking) | High-dose nicotine may modestly augment adenosine-induced heart rate reduction | Generally not clinically significant; no dose adjustment typically needed |
It is important to note that the interaction with caffeine is encountered very frequently in clinical practice. Many patients presenting to the emergency department with SVT have consumed coffee, tea, cola, energy drinks, or other caffeinated beverages. The treating physician should inquire about recent caffeine intake, as this directly affects the likelihood of successful cardioversion with adenosine. In patients with heavy caffeine intake, higher doses may be needed, or an alternative strategy (such as intravenous verapamil, if not contraindicated) may be considered.
The interaction with dipyridamole deserves particular emphasis. Dipyridamole is a nucleoside transport inhibitor that blocks the cellular reuptake of adenosine into red blood cells and endothelial cells. Since this reuptake pathway is the primary mechanism for adenosine's rapid clearance from the bloodstream, dipyridamole dramatically increases both the concentration and duration of action of exogenous adenosine. Patients taking dipyridamole (including combination products like Aggrenox/Asasantin, which contains dipyridamole with aspirin) require dose reduction of at least 75%, and extreme caution is warranted.
What Is the Correct Dosage of Adenosin Macure?
Adenosin Macure must always be administered by a healthcare professional experienced in cardiac rhythm management. The drug is given as a rapid intravenous bolus injection, ideally through a large peripheral vein (antecubital fossa preferred) or, if available, a central venous catheter. Each injection must be followed immediately by a rapid flush of 10–20 ml of 0.9% sodium chloride (normal saline) to ensure the drug reaches the central circulation before it is metabolized.
Adults
SVT Conversion – Standard Adult Dosing
First dose: 6 mg (1.2 ml of 5 mg/ml solution) as a rapid IV bolus over 1–2 seconds, followed immediately by a rapid 10–20 ml normal saline flush
Second dose: If the first dose fails to convert the rhythm within 1–2 minutes, give 12 mg (2.4 ml) as a rapid IV bolus with saline flush
Third dose: If needed, a second 12 mg dose may be given after a further 1–2 minutes
Maximum single dose: 12 mg. Maximum cumulative dose: 30 mg
Diagnostic Use – Tachycardia Assessment
Dose: Same escalating regimen as for SVT conversion (6 mg, then 12 mg, then 12 mg)
Note: The 12-lead ECG should be running continuously during administration to capture any transient changes in atrial activity that become visible during the period of AV block
Children
Paediatric SVT Conversion
Initial dose: 0.1 mg/kg (maximum 6 mg) as a rapid IV bolus with saline flush
Subsequent doses: Increase by 0.1 mg/kg increments (i.e., 0.2 mg/kg, then 0.3 mg/kg) at 1–2 minute intervals if needed
Maximum single dose: 0.3 mg/kg or 12 mg (whichever is lower)
Note: Paediatric dosing should follow local or national resuscitation council guidelines (e.g., European Resuscitation Council, American Heart Association PALS)
Elderly
No specific dose adjustment is required for elderly patients based on age alone. However, elderly patients are more likely to have underlying conduction system disease, sick sinus syndrome, or concomitant medications (such as beta-blockers, calcium channel blockers, or digoxin) that may potentiate adenosine's effects. Clinical judgment should guide dosing, and the initial 6 mg dose should be administered with particular vigilance for prolonged AV block or bradycardia.
Special Populations Requiring Dose Adjustment
| Patient Group | Recommended Dose | Rationale |
|---|---|---|
| Patients on dipyridamole | Start with 0.5–1 mg; increase cautiously | Dipyridamole blocks adenosine reuptake, potentiating effect 4-fold |
| Heart transplant recipients | Start with 1–3 mg; increase cautiously | Denervation supersensitivity causes exaggerated response |
| Patients on carbamazepine | Start with 3 mg; increase cautiously | Carbamazepine potentiates AV nodal blocking effect |
| Central venous access | Start with 3 mg; standard escalation | Reduced transit time and metabolism before reaching heart |
Missed Dose
The concept of a missed dose does not apply to Adenosin Macure. This is not a medication taken on a regular schedule; it is given as a single acute treatment in a medical emergency or diagnostic procedure. Each administration is a discrete therapeutic event supervised by a healthcare professional.
Overdose
Due to adenosine's ultra-short half-life (less than 10 seconds), overdose in the conventional sense is extremely unlikely. Even excessive doses are rapidly cleared from the bloodstream by cellular uptake and enzymatic metabolism. However, if an excessively large dose is given, or if adenosine is administered to a patient taking dipyridamole without appropriate dose reduction, prolonged asystole, severe bradycardia, or profound hypotension could theoretically occur.
Management of suspected overdose or excessive effect is primarily supportive. The self-limiting nature of adenosine's action means that effects typically resolve within 30–60 seconds. If prolonged symptomatic bradycardia occurs, standard measures such as atropine (0.5–1 mg IV), temporary transcutaneous pacing, or IV fluids for hypotension should be employed. Aminophylline (theophylline) can be used as a specific pharmacological antagonist, as methylxanthines competitively block adenosine receptors.
The effectiveness of Adenosin Macure depends critically on correct administration technique. The injection must be given as a rapid bolus (over 1–2 seconds, not slowly) into a large peripheral vein or central line, immediately followed by a rapid 10–20 ml normal saline flush using a three-way stopcock. If a distal peripheral vein (e.g., hand) must be used, elevating the arm during and after injection can help ensure rapid transit to the heart.
What Are the Side Effects of Adenosin Macure?
Like all medicines, Adenosin Macure can cause side effects. However, an important distinction must be made with adenosine: many of the commonly reported “side effects” are actually predictable pharmacological consequences of adenosine receptor activation throughout the body. Because adenosine receptors (A1, A2A, A2B, and A3 subtypes) are expressed on virtually every cell type, a bolus of exogenous adenosine briefly activates receptors beyond just the AV node. The critical reassurance for patients is that adenosine's effects are almost universally self-limiting, typically resolving completely within 30–90 seconds.
Patients should be informed before administration that they may experience several seconds of uncomfortable but transient symptoms, including a sensation of chest tightness, warmth in the face, and brief difficulty breathing. These are expected effects and do not indicate an allergic reaction or dangerous complication in the vast majority of cases.
Very Common (affects more than 1 in 10 patients)
- Facial flushing (warmth and redness of the face and neck)
- Dyspnea (sensation of difficulty breathing or shortness of breath)
- Chest discomfort or pressure (often described as a heavy, tight feeling)
- Transient AV block or asystole (expected pharmacological effect; usually <5 seconds)
- Lightheadedness or dizziness
Common (affects 1 in 10 to 1 in 100 patients)
- Headache
- Nausea
- Metallic taste in the mouth
- Tingling or numbness (paraesthesia), especially in the arms
- Neck, jaw, or throat discomfort
- Sinus bradycardia (slow heart rate following SVT termination)
- Premature ventricular contractions (PVCs) or atrial extrasystoles
- Blurred vision
Uncommon (affects 1 in 100 to 1 in 1,000 patients)
- Hypotension (temporary drop in blood pressure)
- Transient atrial fibrillation or atrial flutter
- Sweating (diaphoresis)
- Palpitations (awareness of heartbeat)
- Hyperventilation
- Abdominal discomfort or nausea
Rare (affects fewer than 1 in 1,000 patients)
- Severe bronchospasm (primarily in patients with asthma or COPD)
- Prolonged asystole or high-degree AV block (>5 seconds)
- Ventricular tachycardia or ventricular fibrillation (very rare)
- Torsades de pointes (in patients with long QT syndrome)
- Seizure-like activity
- Anaphylactoid reactions
- Transient increase in intracranial pressure
Cardiac Side Effects in Detail
The cardiac effects of adenosine deserve special discussion because the brief pause in heartbeat that occurs when adenosine successfully terminates SVT can be alarming to patients. A period of asystole lasting 3–5 seconds is completely normal and expected after adenosine administration. This represents the drug working exactly as intended – transiently blocking AV conduction to interrupt the re-entrant circuit. The sinus node then resumes its role as the primary pacemaker, and normal sinus rhythm is restored. Patients should be warned about this momentary pause in advance.
In some cases, transient atrial fibrillation or atrial flutter may occur immediately after adenosine administration. This has been reported in approximately 1–15% of patients in various studies. In most cases, this is brief and self-terminating within minutes. However, in patients with accessory pathways (such as WPW syndrome), new-onset atrial fibrillation after adenosine could be dangerous because the arrhythmia may conduct rapidly down the accessory pathway, leading to a very fast ventricular rate. This is why adenosine should be given in a setting where defibrillation is immediately available.
Premature ventricular contractions (PVCs), sinus bradycardia, and various degrees of AV block may also be observed transiently after adenosine. Non-sustained ventricular tachycardia has been reported in rare cases but is almost always self-terminating.
Respiratory Side Effects
Dyspnea is one of the most frequently reported side effects, occurring in up to 20–40% of patients. This is mediated by adenosine's activation of carotid body chemoreceptors (simulating hypoxia) and direct stimulation of vagal C-fibres in the lungs. The sensation of breathlessness typically lasts only 10–30 seconds and does not reflect actual oxygen desaturation in the majority of patients. However, in patients with asthma or COPD, true bronchospasm can occur due to adenosine A2B receptor-mediated bronchoconstriction and mast cell mediator release, which is why adenosine is contraindicated in these populations.
It is important to reassure patients before administration that they will likely experience brief but potentially uncomfortable sensations – including chest tightness, warmth in the face, and a feeling that they cannot breathe properly. These are expected effects that will resolve within approximately one minute. Having this information beforehand significantly reduces patient anxiety during and after the injection.
How Should You Store Adenosin Macure?
Adenosin Macure is a hospital-administered medication, and its storage is managed by pharmacy and clinical staff. As a patient, you would not typically need to store this medication yourself. However, the following storage information is important for healthcare professionals and for completeness of the drug information.
The solution should be stored at room temperature, not exceeding 25°C (77°F). It should be protected from light and kept in its original packaging until the time of use. The solution must not be frozen, as freezing can alter the physical properties and potentially the potency of the preparation. Any unused portion of the solution remaining in the vial after single-dose use should be discarded in accordance with local pharmaceutical waste disposal guidelines.
Before administration, the solution should be visually inspected. It should appear as a clear, colourless solution free from visible particles. If the solution appears cloudy, discoloured, or contains particulate matter, it should not be used and should be discarded. Healthcare professionals should also verify the expiry date printed on the vial and carton before use; expired adenosine solutions must not be administered.
As with all medications, Adenosin Macure should be kept out of the sight and reach of children, although given its hospital-only administration route, this is primarily a concern in storage areas rather than in domestic settings.
What Does Adenosin Macure Contain?
Active Ingredient
The active substance is adenosine, present at a concentration of 5 mg per millilitre. Adenosine is a naturally occurring endogenous purine nucleoside composed of an adenine base linked to a ribose sugar (molecular formula: C10H13N5O4, molecular weight: 267.24 g/mol). It is a white, crystalline powder that is sparingly soluble in water at room temperature.
Adenosine is synthesized in every cell of the human body as a product of ATP and S-adenosylhomocysteine metabolism. Its pharmacological activity results from interaction with four known G-protein-coupled receptor subtypes: A1, A2A, A2B, and A3. The antiarrhythmic effect relevant to SVT termination is mediated primarily through A1 receptors on AV nodal myocytes, while the coronary vasodilatory effect used in stress testing is mediated through A2A receptors on vascular smooth muscle cells.
Excipients (Inactive Ingredients)
- Sodium chloride: Added to maintain isotonicity of the solution, ensuring compatibility with blood and tissue fluids during intravenous injection. Each millilitre contains approximately 9 mg of sodium chloride.
- Water for injection: The pharmaceutical-grade solvent used to dissolve the active ingredient and sodium chloride to produce a sterile, pyrogen-free solution suitable for intravenous administration.
The product does not contain preservatives, antimicrobial agents, or buffering systems. The simplicity of the formulation reflects adenosine's adequate stability as a solution at physiological pH and the single-use nature of the product. The absence of preservatives means that any unused portion of the vial should be discarded after opening.
Sodium content: This medicine contains approximately 9 mg of sodium per millilitre, equivalent to approximately 0.45% of the WHO recommended maximum daily dietary intake of 2 g sodium for an adult. A standard 6 mg (1.2 ml) dose contains approximately 10.8 mg sodium, and a 12 mg (2.4 ml) dose contains approximately 21.6 mg sodium. Healthcare professionals should take this into account for patients on sodium-restricted diets, although the amounts involved are small relative to typical dietary sodium intake.
Frequently Asked Questions About Adenosin Macure
Adenosin Macure (adenosine 5 mg/ml) is used primarily for the rapid conversion of paroxysmal supraventricular tachycardia (PSVT) to normal sinus rhythm, including tachycardias associated with accessory bypass tracts such as Wolff-Parkinson-White (WPW) syndrome. It is also used as a diagnostic aid to identify the mechanism of broad or narrow complex tachycardias and in pharmacological cardiac stress testing for myocardial perfusion imaging.
Adenosine works extremely rapidly. When given as a fast intravenous bolus, it typically takes effect within 10 to 30 seconds. Its action is also very brief, with effects lasting only 10 to 20 seconds, due to its ultra-short half-life of less than 10 seconds. This rapid onset and offset is one of the key advantages of adenosine in emergency settings, providing a brief therapeutic window that is sufficient to terminate most SVTs.
The most common side effects include facial flushing (warmth and redness), chest discomfort or pressure, shortness of breath (dyspnea), headache, nausea, and lightheadedness. A brief pause in heartbeat (asystole) or AV block is an expected pharmacological effect, not a true adverse reaction. Nearly all side effects are transient and resolve completely within 1–2 minutes due to adenosine's ultra-short half-life of less than 10 seconds.
Adenosine should generally be avoided in patients with asthma or severe COPD. It can cause bronchospasm by activating adenosine A2B receptors on bronchial smooth muscle and promoting mast cell mediator release. In patients with reactive airway disease, adenosine can trigger severe, potentially life-threatening bronchospasm. If there is no alternative and adenosine must be used, it should only be administered in a fully equipped resuscitation setting with careful monitoring and immediate access to bronchodilators.
Caffeine and theophylline are methylxanthines that act as competitive antagonists at adenosine receptors, particularly the A1 and A2A subtypes. Because adenosine must bind to A1 receptors on the AV node to exert its antiarrhythmic effect, the presence of caffeine blocks these receptors and reduces or eliminates adenosine's therapeutic action. Patients who have recently consumed significant amounts of caffeine may require higher doses or an alternative antiarrhythmic agent.
Adenosine is generally considered one of the safer antiarrhythmic options during pregnancy for treating SVT. Its ultra-short half-life (less than 10 seconds) means that fetal exposure is minimal, as the drug is almost entirely metabolized before it can cross the placenta in significant amounts. Professional guidelines from the AHA, ESC, and HRS include adenosine as a first-line option for SVT in pregnancy. However, it should still be administered only in a monitored healthcare setting with resuscitation equipment available.
References
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This article was written and reviewed by the iMedic Medical Editorial Team, comprising licensed specialist physicians with expertise in cardiology, electrophysiology, and clinical pharmacology.
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