This medication slows AV conduction from the SA node through the AV node, which abolishes tachyarrhythmias. It does this by essentially acting as a short term calcium channel blocker inside the AV node that is induced by cyclic AMP (CAMP). This leads to a prolonged PR interval on the ECG.
Adenosine is indicated for specific types of tachyarrhythmias that originate above the AV node or that use the AV node as re-entry, such as PSVT (paroxysmal supraventricular tachycardia). Atrial fibrillation, atrial flutter, and ventricular arrhythmias are not terminated by adenosine because they do not typically involve the AV node as part of the re-entrant circuit.
It is not uncommon for patients to experience a brief (10 second) episode of bradycardia or even brief asystole. This is self-limiting and they typically return to a heart rate of a normal range quickly as this medication increases the PR interval and induces an AV block.
Transient flushing is possible as this medication causes brief small vessel vasodilation. In some patients they may experience a brief episode of hypotension, dizziness or palpitations.
Most commonly a few seconds after administration, patients will feel a moment of breathlessness or dyspnea sometimes described as if they had just been hit in the chest. This is because adenosine can induce a brief bronchoconstriction.
This medication is given in a rapid IV push, followed by a saline flush. It is given in this way because its half life is only a few seconds in duration. To maximize the effects of the medication it should be administered in an IV as close to the heart as possible.
Remember that caffeine increases your heart rate. Patients who consume large amounts of caffeine or take the medication theophylline require larger doses of adenosine to reach therapeutic effects. This is because they are methylxanthines and they block the receptors for adenosine on the heart.
Dipyridamole (Persantine) is an antiplatelet medication that blocks the uptake and metabolism of this medication, and may intensify its effects, especially side effects. Patients taking this medication may experience more serious side effects due to an interaction that intensifies the effects.
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