Adenosine in the Episodic Treatment of Paroxysmal Supraventricular Tachycardia

The pharmacology, pharmacokinetics, clinical efficacy, adverse effects, and dosage and administration of adenosine in the treatment of episodes of paroxysmal supraventricular trachycardia (PSVT) are reviewed. Adenosine is an endogenous adenine nucleoside that markedly decreases heart rate and prolongs atrioventricular (AV)-nodal conduction. Adenosine is rapidly cleared from plasma by the cellular elements of the blood and by vascular endothelial cells and subjected to enzymatic metabolism. The drug has a half-life of 0.6 to 10 seconds. In noncomparative clinical trials, adenosine terminated 85% to 100% of induced or spontaneous episodes of PSVT involving the AV node in the reentrant circuit. In patients with arrhythmias that do not involve the AV node in the reentrant circuit, adenosine produces AV block and does not restore sinus rhythm. Prospective, randomized trials comparing adenosine with verapamil in adults have not yet been performed. The adverse effects of adenosine include flushing, dyspnea, headache, cough, chest pain, sinus bradycardia, atrial fibrillation, ventricular arrhythmias, and various degrees of AV block. Because of the short half-life of adenosine, these effects are transient and well tolerated. The initial dose of adenosine in treating acute PSVT is 6 mg given by rapid i.v. bolus injection, followed in one to two minutes by up to two additional 12-mg boluses if necessary. Adenosine has been found to be effective in terminating PSVT and thus offers an alternative to verapamil. Prospective, randomized trials comparing adenosine with verapamil are needed to definitively establish adenosine's role in the therapy of PSVT.