Adenosine Dosage for Supraventricular Tachycardia (SVT)
Adenosine is a first-line pharmacologic treatment for stable, regular narrow-complex tachycardia, commonly known as supraventricular tachycardia (SVT) [1][2]. The standard initial dose for adults is 6 mg administered as a rapid intravenous bolus [1][3]. This rapid administration is crucial because of adenosine's very short half-life, typically less than 10 seconds [1].
What Happens If the First Adenosine Dose Doesn't Work?
If the initial 6 mg dose of adenosine does not terminate the SVT, a second, higher dose of 12 mg can be administered intravenously [1][3]. In some cases, a third dose of 12 mg may be given if the SVT persists after the second dose [1].
How is Adenosine Administered for SVT?
Adenosine is given as a rapid intravenous push, often directly into a large-bore IV line or central line [1]. To maximize the drug's effect and minimize discomfort, it is frequently administered with a concurrent rapid saline flush [1][2]. This rapid infusion pushes the adenosine quickly through the circulation to the heart [1].
Why is Adenosine Effective for SVT?
Adenosine works by transiently blocking the electrical conduction through the atrioventricular (AV) node [1][2]. The AV node is a critical relay station for electrical signals in the heart that is often involved in the reentrant circuits causing SVT [1][2]. By temporarily interrupting conduction at the AV node, adenosine can break the reentrant pathway and restore a normal heart rhythm [1][2].
What are the Side Effects of Adenosine?
Patients often experience transient, but generally mild and self-limiting, side effects during or immediately after adenosine administration [1][2]. These can include flushing, shortness of breath or chest tightness, dizziness, headache, nausea, and a brief period of asystole or bradycardia [1][2]. These effects are typically short-lived due to the drug's rapid metabolism by red blood cells and vascular endothelium [1].
Are There Any Contraindications for Adenosine?
Adenosine should be used with caution or avoided in certain patient populations [1]. These include individuals with known hypersensitivity to adenosine, high-degree atrioventricular block (second- or third-degree block) unless a pacemaker is in place, or patients with sick sinus syndrome, unless a pacemaker is present [1]. It is also used cautiously in those with active bronchospasm or asthma, as it can cause bronchoconstriction [1]. In patients with irregular wide-complex tachycardias, adenosine may be less effective and potentially harmful, so a careful rhythm analysis is always required before administration [1].
What is the Availability and Cost of Adenosine?
Adenosine is a widely available generic medication, making it a cost-effective treatment option for SVT [4]. It is typically supplied in vials or syringes for intravenous administration [4].
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Sources:
1. DrugPatentWatch.com
2. UpToDate
3. American Heart Association Guidelines
4. Lexicomp