Substance: Adenosine
Brand names: Adenocor
Mechanism of action
Adenosine works by slowing down the impulse transmission through the atrioventricular (AV) node, thereby interfering with the pathway that enables reentry tachyarrhythmias (AVNRT and AVRT). These arrhythmias rely on AV node transmission. By disrupting this transmission, the reentry- and hence, the arrhythmia- may be terminated. Generally, adenosine is considered safe for patients with narrow complex tachycardia (NCT).
Adenosine typically causes a short-lasting second- or third-degree AV block which may be unpleasant to the patient. This side effect lasts a few seconds. Case reports have indicated that the risk of high-degree AV block and ventricular arrhythmias is greater in patients on digoxin or verapamil, although this is not an established drug interaction.
The half-life of adenosine is 8 seconds. Adverse effects are therefore very brief.
Indications
- Paroxysmal supraventricular tachycardia (PSVT), which includes forms that are caused by pre-excitation.
- Myocardial perfusion scintigraphy.
Contraindications
- Asthma and COPD. Adenosine has caused mild to moderate exacerbation of asthma symptoms. Adenosine should be used with caution in patients with obstructive lung disease or asthma.
- Irregular wide complex tachycardia (absolute contraindication).
- Irregular wide complex tachycardia is most often due to atrial fibrillation with wide QRS complexes due to bundle branch blocks or other conduction defects. However, in rare instances, it may be due to pre-excited atrial fibrillation (i.e. atrial fibrillation with impulses conducted via an accessory pathway [see Wolff-Parkinson-White Syndrome]); blocking AV node conduction may result in accelerated transmission of atrial impulses to the ventricles and thus ventricular fibrillation and cardiac arrest.
- High-degree AV block (second-degree Mobitz type 2 AV block, third-degree AV block).
- Sick sinus syndrome or symptomatic bradycardia in the absence of a pacemaker.
- Hypersensitivity to adenosine.
Administration
- Normal route: Peripheral intravenous (IV).
- Alternative route: Central venous administration of adenosine is suitable in the intensive care unit or coronary care unit.
- Adenosine injection must be administered quickly (1-2 seconds), followed immediately by a rapid saline flush (use a three-way tap system).
- Compatible IV fluids: normal saline.
- Storage: room temperature.
Dosage
Adults
- Initial dose: 6 mg
- Wait 60 seconds before attempting a second dose.
- Second dose: 12 mg.
- Wait 60 seconds before attempting a third dose.
- Third dose: 12 or 16 mg.
Renal failure or renal replacement therapy
- No dosage adjustment is required in renal failure or renal replacement therapy.
Pediatric patients
- Body weight < 50 kg:
- Initial dose: 0.05 to 0.1 mg/kg
- Second dose: Increase the dose by 0.05 to 0.1 mg/kg.
- Maximum single dose: 0.3 mg/kg
- Body weight >50 kg:
- Adult dosage.
Adverse effects
Adverse effects typically persist <10 seconds due to the short half-life of adenosine.
- Anxiety
- Chestpain.
- Palpitations.
- Headache
- Hypotension.
- Facial flushing.
- Sweating.
- Bronchospasm
- Dyspnea
- Nausea
- Metallic taste
- Tightness in throat
- Lightheadedness, dizziness, tingling in arms, numbness, blurred vision, burning sensation.
Relevant reading
References
Zipes et al: Arrhythmology, Elsevier (2019).
Wellington ICU Drug Manual
