Adenosine is administered intravenously for the treatment of supraventricular tachycardia (SVT) [1]. The standard dose for adults typically begins with a rapid bolus injection of 6 milligrams (mg), followed by a second bolus of 12 mg if the arrhythmia does not convert [1][2]. In some cases, a third dose of 12 mg may be given if the SVT persists [2]. The drug is given very rapidly, often over a few seconds, to quickly reach the heart [1]. Its effect is transient, with a half-life of less than 10 seconds, necessitating immediate administration to be effective [3].
What is SVT and How Does Adenosine Treat It?
Supraventricular tachycardia (SVT) is a condition characterized by a rapid heart rate originating from the atria or the atrioventricular (AV) node [4]. Adenosine works by temporarily slowing conduction through the AV node, which is often the pathway involved in SVT re-entry circuits [3][5]. By blocking conduction at the AV node, adenosine can interrupt the re-entrant loop, allowing the heart's natural pacemaker to re-establish a normal sinus rhythm [3].
How is Adenosine Administered for SVT?
Adenosine is administered as a rapid intravenous bolus injection, meaning it is pushed quickly into a vein [1][2]. This rapid administration is crucial due to adenosine's very short half-life, which is less than 10 seconds [3]. A saline flush follows the adenosine injection to ensure the entire dose reaches the central circulation [1]. Continuous electrocardiogram (ECG) monitoring is essential during administration to assess the heart rhythm and the drug's effect [2].
What Are the Potential Side Effects of Adenosine?
Patients may experience transient side effects during and immediately after adenosine administration, such as flushing, chest pain or pressure, shortness of breath, and a sensation of impending doom [2][6]. These effects are typically brief, lasting only seconds to a minute, and are related to the drug's vasodilatory and AV nodal blocking properties [3][6]. Other less common side effects can include headache, dizziness, nausea, and transient bradycardia or AV block [6].
Are There Any Contraindications for Adenosine Use?
Adenosine is generally not recommended for patients with certain heart conditions, including high-grade AV block (second- or third-degree heart block) or sick sinus syndrome, unless a pacemaker is in place [2][6]. It should also be used with caution in patients with asthma or active bronchospasm, as it can cause bronchoconstriction [6]. Patients taking certain medications, such as dipyridamole or carbamazepine, may require dose adjustments or may not be suitable candidates for adenosine [6].
What is the Typical Duration of Adenosine's Effect?
The therapeutic effect of adenosine on the AV node is extremely short-lived, lasting only seconds [3]. Its half-life is less than 10 seconds, meaning it is rapidly metabolized by red blood cells and vascular endothelium [3]. This short duration of action allows for quick assessment of the underlying rhythm and necessitates that the drug be delivered as a rapid bolus to be effective in interrupting SVT [1][3].