Adenosine is a medication used to treat supraventricular tachycardia (SVT) [1]. The typical dosage for adenosine in SVT is an initial rapid intravenous (IV) bolus of 6 mg [2]. If this dose is ineffective in terminating the SVT, a second, larger dose of 12 mg can be administered as another rapid IV bolus [2]. In some cases, a third dose of 12 mg may be given if the SVT persists after the second dose [2].
What is the mechanism of adenosine in treating SVT?
Adenosine works by slowing electrical conduction through the atrioventricular (AV) node, which is often involved in the reentrant circuits that cause SVT [3]. It binds to adenosine receptors on the AV node, leading to a transient block of conduction [3]. This interruption of the electrical pathway can terminate the rapid heart rhythm characteristic of SVT [3].
How is adenosine administered for SVT?
Adenosine is administered intravenously as a rapid bolus [2]. Due to its very short half-life (less than 10 seconds), it must be injected quickly, typically over a few seconds, followed immediately by a saline flush [1][2]. This rapid administration ensures that the drug reaches the heart and exerts its effect before being rapidly metabolized [1]. Continuous cardiac monitoring is essential during administration to assess the response and detect any adverse effects [1].
What are the potential side effects of adenosine?
While generally well-tolerated, adenosine can cause transient side effects [1]. These commonly include flushing, shortness of breath, chest discomfort or pressure, and a brief period of asystole (cessation of heart rhythm) or bradycardia (slow heart rate) [1][4]. Patients may also experience dizziness, nausea, or headache [1]. These effects are typically short-lived, resolving within seconds to minutes due to the drug's rapid metabolism [1].
How long does adenosine take to work for SVT?
Adenosine acts very quickly, with its effects on the AV node occurring within seconds of administration [1]. If it is effective in terminating the SVT, the heart rhythm usually converts to normal sinus rhythm almost immediately [2].
Are there alternatives to adenosine for SVT treatment?
Other pharmacological treatments for SVT include calcium channel blockers and beta-blockers, which also work by slowing AV nodal conduction [3]. In some cases, vagal maneuvers, such as the Valsalva maneuver, may be attempted before or alongside pharmacological interventions [4]. If SVT is recurrent or resistant to medication, catheter ablation, a procedure to permanently block the abnormal electrical pathway, may be considered [3].
Who should not receive adenosine?
Adenosine is generally contraindicated in patients with certain heart conditions, including high-grade atrioventricular block (unless a pacemaker is in place), sick sinus syndrome, and known or suspected bronchoconstrictive lung disease (such as asthma), as it can cause bronchospasm [1][4]. It should also be used with caution in patients with heart failure or valvular heart disease [1].