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Adenosine

Comprehensive Guide to Adenosine: Uses, Dosage, Side Effects, and More

What is Adenosine?

Adenosine is a naturally occurring nucleoside used as a medication to diagnose and treat specific heart rhythm disorders, primarily supraventricular tachycardia (SVT). As an antiarrhythmic agent, this drug slows electrical conduction in the heart by acting on adenosine A1 receptors, effectively restoring normal heart rhythm. Marketed under brand names like Adenocard and Adenoscan, the treatment is administered intravenously in clinical settings and is valued for its rapid onset and short duration of action. The medication’s benefits include its efficacy in terminating SVT episodes and aiding in diagnostic stress testing, but it requires careful administration due to risks of transient heart block or hypotension.

Overview of Adenosine

Generic Name: Adenosine

Brand Name: Adenocard (therapeutic), Adenoscan (diagnostic), generics

Drug Group: Antiarrhythmic agent; nucleoside

The drug is used to

  • Treat paroxysmal supraventricular tachycardia (PSVT), including Wolff-Parkinson-White syndrome.
  • Perform diagnostic myocardial perfusion imaging (stress testing) in patients unable to exercise.
  • Off-label uses include management of certain ventricular tachycardias or pulmonary hypertension under specialist guidance.

Key Characteristics

Form: Intravenous injection (3 mg/mL vials for Adenocard; 3 mg/mL for Adenoscan).

Mechanism: Activates adenosine A1 receptors, slowing atrioventricular (AV) node conduction and interrupting reentrant pathways.

Two vials of Adenosine Injection USP, one 12 mg/4 mL and one 6 mg/2 mL, both clearly labeled for rapid bolus IV use, commonly used for supraventricular tachycardia.
Adenosine Injection USP, available in 6 mg/2 mL and 12 mg/4 mL single-dose vials, is a rapid-acting medication administered intravenously to treat supraventricular tachycardia (SVT).

Approval: FDA-approved (1989 for Adenocard, 1995 for Adenoscan) and EMA-approved for SVT and stress testing.

Indications and Uses of Adenosine

Adenosine is indicated for:

Paroxysmal Supraventricular Tachycardia (PSVT): Rapidly converts PSVT to normal sinus rhythm in adults and children.

Myocardial Perfusion Imaging: Acts as a pharmacologic stress agent for cardiac imaging in patients unable to perform exercise stress tests.

Off-Label Uses: May be used for wide-complex tachycardias or pulmonary hypertension in specialized settings.

Note: The medication is for acute use in clinical settings and not for long-term management. It should be administered by trained professionals due to its rapid effects and potential adverse reactions.

Dosage of Adenosine

Important Note: Adenosine must be administered by a healthcare professional in a clinical setting with cardiac monitoring. Dosage is weight-based and condition-specific.

Dosage for Adults

PSVT (Adenocard):

  • Initial: 6 mg IV as a rapid bolus over 1–2 seconds, followed by a 20 mL saline flush.
  • If no response within 1–2 minutes: 12 mg IV bolus, repeated once if needed.
  • Maximum single dose: 12 mg.

Myocardial Perfusion Imaging (Adenoscan): 140 mcg/kg/min IV infusion over 6 minutes (total dose adjusted by weight, e.g., ~10 mg for a 70 kg patient).

Dosage for Children

PSVT (Adenocard):

  • Initial: 0.1 mg/kg IV bolus (maximum 6 mg), followed by saline flush.
  • If no response: Increase by 0.1 mg/kg (maximum 12 mg), repeated as needed.

Myocardial Perfusion Imaging: Not typically used in children; consult a pediatric cardiologist.

Dosage for Pregnant Women

Pregnancy Category C: Limited data; use only if benefits outweigh risks, as transient fetal bradycardia may occur. Consult a cardiologist.

Dosage Adjustments

Renal/Hepatic Impairment: No specific adjustments; monitor for prolonged effects in severe cases.

Drug Interactions: Adjust doses if used with dipyridamole or theophylline (see Drug Interactions).

Obese Patients: Use ideal body weight for myocardial perfusion dosing to avoid overdose.

Additional Considerations

  • Administer via a large peripheral vein or central line to ensure rapid delivery.
  • Use continuous ECG monitoring during administration.

How to Use Adenosine

Administration: The drug is given as a rapid IV bolus (for PSVT) or continuous infusion (for stress testing) by trained professionals in a hospital or clinic with resuscitation equipment.

PSVT: Administer 6 mg or 12 mg bolus over 1–2 seconds via a peripheral IV, followed by a 20 mL saline flush to ensure delivery to the heart.

Stress Testing: Infuse at 140 mcg/kg/min over 6 minutes using an infusion pump, with radionuclide imaging performed concurrently.

Monitoring: Continuous ECG, blood pressure, and respiratory monitoring are required during and after administration.

Missed Dose: Not applicable, as the medication is given acutely by professionals.

Additional Tips:

  • Report chest pain, shortness of breath, or dizziness immediately during administration.
  • Avoid caffeine or theophylline-containing products before stress testing, as they block Adenosine’s effects.

Contraindications for Adenosine

The medication is contraindicated in:

  • Patients with hypersensitivity to Adenosine or its components.
  • Those with second- or third-degree AV block or sick sinus syndrome (unless a pacemaker is in place).
  • Patients with bronchoconstrictive diseases (e.g., severe asthma, COPD) due to risk of bronchospasm.
  • Those with severe hypotension or decompensated heart failure.

Warnings & Precautions for Adenosine

General Warnings

Heart Block: The drug may cause transient AV block or asystole; use with ECG monitoring and resuscitation equipment available.

Bronchospasm: Risk of severe bronchoconstriction in patients with asthma or COPD; use cautiously or avoid.

Hypotension: May cause transient low blood pressure, particularly during stress testing; monitor closely.

Arrhythmias: Risk of new arrhythmias (e.g., atrial fibrillation, ventricular tachycardia) during administration.

Seizures: Rare risk of seizures, particularly in susceptible patients.

Use in Specific Populations

Pregnancy: Category C; limited data suggest transient fetal effects. Use only if essential, with fetal monitoring.

Breastfeeding: Unknown if excreted in breast milk; use cautiously due to short half-life.

Elderly: Increased risk of hypotension and arrhythmias; monitor closely.

Children: Safe for PSVT in pediatric patients; weight-based dosing required.

Renal/Hepatic Impairment: No significant impact due to rapid clearance, but monitor for prolonged effects.

Additional Precautions

  • Inform your doctor about heart conditions, asthma, or recent caffeine/theophylline use.
  • Avoid driving or operating machinery immediately after administration due to potential dizziness.

Overdose and Management of Adenosine

Overdose Symptoms

Overdose is rare due to rapid metabolism but may cause:

  • Prolonged asystole or heart block.
  • Severe hypotension or bradycardia.
  • Bronchospasm or respiratory distress.

Immediate Actions

Stop Administration: Discontinue the drug immediately.

Supportive Care: Administer fluids for hypotension; use atropine or pacing for bradycardia.

Monitor: Continuous ECG and vital sign monitoring until symptoms resolve.

Additional Notes

  • Overdose effects are short-lived due to Adenosine’s half-life (seconds).
  • Store securely in clinical settings to prevent misuse.

Side Effects of Adenosine

Common Side Effects

  • Flushing (18–44%)
  • Chest discomfort or pain (12–40%)
  • Dyspnea (12–28%)
  • Headache (2–18%)
  • Lightheadedness or dizziness (2–12%)
    These effects are transient, resolving within seconds to minutes.

Serious Side Effects

Seek immediate medical attention for:

Cardiac: Prolonged asystole, severe bradycardia, or new arrhythmias.

Respiratory: Bronchospasm or severe shortness of breath.

Allergic Reactions: Rare; rash, hives, or anaphylaxis.

Neurologic: Seizures or loss of consciousness.

Additional Notes

  • Side effects are brief due to the drug’s rapid clearance.
  • Report persistent symptoms immediately, though rare.

Drug Interactions with Adenosine

The treatment may interact with:

Dipyridamole: Enhances Adenosine’s effects, increasing risk of heart block; reduce dose (e.g., 25–50% of standard).

Theophylline, Caffeine: Block Adenosine receptors, reducing efficacy; avoid before administration.

Digoxin, Verapamil: Increase risk of ventricular arrhythmias; monitor closely.

Carbamazepine: May enhance AV block; use with caution.

Action: Inform your healthcare provider of all medications, supplements, and recent caffeine/theophylline intake.

Patient Education or Lifestyle

Preparation: Avoid caffeine (e.g., coffee, tea, energy drinks) for 12–24 hours before stress testing, as it blocks the medication’s effects.

Monitoring: Report chest pain, breathing difficulty, or dizziness during or after administration.

Lifestyle: Maintain a heart-healthy diet and exercise (as advised) to manage underlying conditions like SVT.

Follow-Up: Attend follow-up appointments to assess heart rhythm or stress test results.

Emergency Awareness: Carry information about your condition (e.g., SVT) and medications for emergencies.

Activity: Avoid strenuous activity immediately after administration due to potential dizziness.

Pharmacokinetics of Adenosine

Absorption: Administered IV; not applicable for oral absorption.

Distribution: Rapidly distributed in extracellular fluid; taken up by erythrocytes and endothelial cells.

Metabolism: Rapidly metabolized to inosine and AMP via adenosine deaminase and phosphorylation.

Excretion: Cleared as metabolites; negligible unchanged excretion.

Half-Life: <10 seconds, ensuring transient effects.

Pharmacodynamics of Adenosine

Adenosine exerts its effects by:

  • Activating A1 receptors on cardiac cells, slowing AV node conduction and interrupting reentrant pathways in PSVT.
  • Causing coronary vasodilation, used in stress testing to mimic exercise-induced myocardial demand.
  • Inducing transient AV block, restoring sinus rhythm in SVT.
  • Acting rapidly with minimal systemic persistence due to short half-life.

Storage of Adenosine

Temperature: Store vials at room temperature (15–30°C or 59–86°F); do not refrigerate or freeze.

Protection: Keep in original packaging to protect from light.

Safety: Store securely in clinical settings; only healthcare professionals should handle.

Disposal: Follow local regulations or consult a pharmacist for safe disposal of unused medication.

Frequently Asked Questions (FAQs)

Q: What does Adenosine treat?
A: The drug treats supraventricular tachycardia (SVT) and is used in cardiac stress testing.

Q: Is Adenosine safe for asthma patients?
A: No, it’s contraindicated in severe asthma or COPD due to bronchospasm risk.

Q: How quickly does Adenosine work?
A: The medication acts within seconds to restore normal heart rhythm in SVT.

Q: Can I drink coffee before an Adenosine stress test?
A: No, avoid caffeine for 12–24 hours, as it reduces the drug’s effectiveness.

Q: Are Adenosine’s side effects long-lasting?
A: No, side effects (e.g., flushing, chest pain) resolve within seconds to minutes.

Regulatory Information

The medication is approved by:

U.S. Food and Drug Administration (FDA): Approved in 1989 (Adenocard for SVT) and 1995 (Adenoscan for stress testing).

European Medicines Agency (EMA): Approved for SVT and myocardial perfusion imaging.

Other Agencies: Approved globally for similar indications; consult local guidelines.

Disclaimer: This article provides general information about Adenosine for educational purposes only and is not a substitute for professional medical advice. Always consult a qualified healthcare provider, such as a cardiologist, before using this drug or making any medical decisions. Improper use of this medication can lead to serious health risks, including severe heart rhythm disturbances or respiratory complications.

References

  1. U.S. Food and Drug Administration (FDA). (2023). Adenocard (Adenosine) Prescribing Information.
    • Official FDA documentation detailing the drug’s approved uses, dosage, and safety for SVT.
  2. European Medicines Agency (EMA). (2023). Adenosine Summary of Product Characteristics.
    • EMA’s comprehensive information on the medication’s indications and precautions in Europe.
  3. National Institutes of Health (NIH). (2023). Adenosine: MedlinePlus Drug Information.
    • NIH resource providing detailed information on the drug’s uses, side effects, and precautions.
  4. World Health Organization (WHO). (2023). WHO Model List of Essential Medicines: Adenosine.
    • WHO’s inclusion of Adenosine as an essential medicine for SVT.
  5. Journal of the American College of Cardiology. (2019). Adenosine in the Management of Supraventricular Tachycardia.
    • Peer-reviewed article on the medication’s efficacy in SVT (note: access may require a subscription).

Dr. Andrew Parker is a board-certified internal medicine physician with over 10 years of clinical experience. He earned his medical degree from the University of California, San Francisco (UCSF), and has worked at leading hospitals including St. Mary’s Medical Center. Dr. Parker specializes in patient education and digital health communication. He now focuses on creating clear, accessible, and evidence-based medical content for the public.

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