Usage
Adenosine triphosphate (ATP) is primarily indicated for the conversion of paroxysmal supraventricular tachycardia (PSVT) to sinus rhythm. It is also used in myocardial perfusion imaging studies. ATP’s pharmacological classification is as an antiarrhythmic agent. It slows conduction time through the atrioventricular (AV) node, interrupting re-entry pathways responsible for PSVT.
Alternate Names
Adenosine. Brand names include Adenocard, Adenoscan, and Adeno-jec.
How It Works
Pharmacodynamics: ATP exerts its antiarrhythmic effect primarily by slowing conduction through the AV node. This is achieved by activating A1 adenosine receptors, which leads to hyperpolarization of cardiac cells and抑制 of adenylate cyclase, reducing cAMP levels. This results in a transient AV block.
Pharmacokinetics: ATP is administered intravenously and has an extremely short half-life (less than 10 seconds), primarily due to rapid cellular uptake and metabolism by adenosine deaminase and adenosine kinase. It is metabolized to inosine and adenosine monophosphate. Elimination is rapid, mainly through renal excretion of metabolites.
Mode of Action: ATP binds to A1 adenosine receptors on cardiac cells. This binding results in the opening of potassium channels, leading to an efflux of potassium ions and membrane hyperpolarization. Concurrently, calcium channel opening is inhibited, further reducing cellular excitability and slowing conduction velocity, particularly in the AV node.
Elimination Pathways: Rapid metabolism within erythrocytes and vascular endothelial cells to inosine and adenosine monophosphate. Renal excretion is the primary elimination pathway for these metabolites.
Dosage
Standard Dosage
Adults:
For PSVT: Initial dose of 6 mg as a rapid IV bolus over 1-2 seconds, followed by a saline flush. If PSVT persists, a 12 mg bolus can be given after 1-2 minutes, followed by a final 12 mg bolus if necessary.
For Myocardial Perfusion Imaging: 140 mcg/kg/min as a continuous IV infusion for 6 minutes.
Children:
For PSVT (less than 50 kg): Initial dose of 50-100 mcg/kg rapid IV bolus. Subsequent doses may be increased by 50-100 mcg/kg increments every 1-2 minutes until sinus rhythm is achieved (maximum single dose: 300 mcg/kg).
Special Cases:
Elderly Patients: Start with lower doses and monitor closely.
Patients with Renal Impairment: Caution is advised, as metabolites are renally cleared. Dosage adjustments may be required.
Patients with Hepatic Dysfunction: No specific dosage adjustments are routinely required.
Patients with Comorbid Conditions: Use with caution in patients with pre-existing lung conditions like asthma or COPD, heart conditions (e.g., 2nd/3rd degree AV block, sick sinus syndrome, long QT syndrome, heart failure, hypotension, recent MI), or cerebrovascular disease.
Clinical Use Cases
- Intubation: Not routinely used.
- Surgical Procedures: May be used to treat intraoperative PSVT.
- Mechanical Ventilation: Not routinely used.
- Intensive Care Unit (ICU) Use: Used for managing PSVT.
- Emergency Situations: PSVT.
Dosage Adjustments: Renal and hepatic impairment may require dose reduction.
Side Effects
Common Side Effects:
Flushing, dyspnea, chest pain, lightheadedness, headache, nausea. These are typically transient and self-limiting due to ATP’s short half-life.
Rare but Serious Side Effects:
Severe bradycardia, high-degree AV block, bronchospasm, hypotension, atrial fibrillation.
Long-Term Effects: Not applicable due to the drug’s short half-life.
Adverse Drug Reactions (ADR): Severe bronchospasm, significant bradycardia, prolonged asystole.
Contraindications
Second or third-degree AV block (except in patients with a functioning pacemaker), sick sinus syndrome (except in patients with a functioning pacemaker), hypersensitivity to adenosine, bronchoconstrictive or bronchospastic lung disease, severe hypotension.
Drug Interactions
Dipyridamole and carbamazepine potentiate adenosine’s effects and require dosage reductions. Methylxanthines (theophylline, caffeine) antagonize adenosine’s effects. There may be interactions with other drugs affecting cardiac conduction.
Pregnancy and Breastfeeding
Pregnancy Safety Category: C (FDA). Use only if clearly needed and the benefit outweighs the risk. Data on breastfeeding is limited; use cautiously.
Drug Profile Summary
- Mechanism of Action: Slows AV nodal conduction by activating A1 adenosine receptors.
- Side Effects: Flushing, dyspnea, chest pain, headache, nausea, bradycardia.
- Contraindications: AV block, sick sinus syndrome, hypersensitivity, lung disease.
- Drug Interactions: Dipyridamole, carbamazepine, methylxanthines.
- Pregnancy & Breastfeeding: Use with caution if clearly needed.
- Dosage: 6 mg IV bolus for PSVT (adults), with potential 12 mg repeat doses.
- Monitoring Parameters: ECG, heart rate, blood pressure, oxygen saturation.
Popular Combinations: Not typically used in combination therapies for its primary indication.
Precautions
- Assess for contraindications and drug interactions prior to administration. Monitor cardiac rhythm and vital signs closely during and after administration.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for ATP for PSVT?
A: 6 mg rapid IV bolus initially, followed by 12 mg boluses as needed, for adults. Pediatric dosing is weight-based.
Q2: What is the mechanism of action of ATP?
A: Activates A1 adenosine receptors, slowing AV nodal conduction.
Q3: What are the common side effects of ATP administration?
A: Flushing, dyspnea, chest pain, dizziness, and headache.
Q4: What are the contraindications for ATP use?
A: Second or third-degree AV block, sick sinus syndrome, hypersensitivity, bronchospastic lung disease.
Q5: How is ATP administered?
A: Rapid intravenous bolus.
Q6: Does ATP interact with other medications?
A: Yes, notably with dipyridamole, carbamazepine, and methylxanthines.
Q7: Can ATP be used during pregnancy or breastfeeding?
A: Use with caution if clearly needed, as data is limited.
Q8: What are the key monitoring parameters during ATP administration?
A: Continuous ECG monitoring, heart rate, blood pressure, and oxygen saturation.
Q9: How should ATP be administered in patients with renal insufficiency?
A: With caution and potential dose adjustments, as metabolites are renally cleared.
Q10: What should be done if the initial dose of ATP is ineffective?
A: Repeat bolus doses (12 mg for adults) may be given at 1-2 minute intervals if PSVT persists.
