Methylxanthines act as competitive antagonists of adenosine and can blunt its pharmacological effects. caffeine found in coffee, theophylline found in tea, or theobromine found in chocolate) have a purine structure and bind to some of the same receptors as adenosine. The recommended dose is also reduced by half in patients presenting congestive heart failure, myocardial infarction, shock, hypoxia, and/or chronic liver disease or chronic kidney disease, and in elderly patients.ĭipyridamole potentiates the action of adenosine, requiring the use of lower doses.Ĭaffeine's principal mode of action is as an antagonist of adenosine receptors in the brain. The dose is often decreased in patients on dipyridamole (Persantine) and diazepam (Valium) because adenosine potentiates the effects of these drugs. The recommended dose may be increased in patients on theophylline since methylxanthines prevent binding of adenosine at receptor sites. When given to dilate the arteries, such as in a "stress test", the dosage is typically 0.14 mg/kg/min, administered for 4 or 6 minutes, depending on the protocol. If this has no effect (i.e., no evidence of transient AV block), a dose of 12 mg can be given 1–2 minutes after the first dose. The IV push is often followed with a flush of 10–20 mL of normal saline. Due to adenosine's extremely short half-life, the IV line is started as proximal (near) to the heart as possible, such as the antecubital fossa. When given for the evaluation or treatment of a supraventricular tachycardia (SVT), the initial dose is 6 mg to 12 mg, depending on standing orders or provider preference, given as a rapid parenteral infusion. Nuclear stress test Īdenosine is used as an adjunct to thallium (TI 201) or technetium (Tc99m) myocardial perfusion scintigraphy (nuclear stress test) in patients unable to undergo adequate stress testing with exercise. This can be disconcerting to a normally conscious patient, and is associated with angina-like sensations in the chest. When adenosine is used to cardiovert an abnormal rhythm, it is normal for the heart to enter ventricular asystole for a few seconds. īecause of the effects of adenosine on AV node-dependent SVTs, adenosine is considered a class V antiarrhythmic agent. However, the ventricular response rate is temporarily slowed with adenosine in such cases. įast rhythms of the heart that are confined to the atria (e.g., atrial fibrillation and atrial flutter) or ventricles (e.g., monomorphic ventricular tachycardia), and do not involve the AV node as part of the re-entrant circuit, are not typically converted by adenosine. In addition, atrial tachycardia can sometimes be terminated with adenosine. This includes any re-entrant arrhythmias that require the AV node for the re-entry, e.g., AV reentrant tachycardia (AVRT) and AV nodal reentrant tachycardia (AVNRT). Ĭertain SVTs can be successfully terminated with adenosine. In individuals with supraventricular tachycardia (SVT), adenosine is used to help identify and convert the rhythm. Medical uses Supraventricular tachycardia It is found in adenosylcobalamin (an active form of vitamin B12 ) and as a radical in radical SAM enzymes. Adenosine is used as an intravenous medication for some cardiac arrhythmias.Īdenosyl (abbreviated Ado or 5'-dAdo) is the chemical group formed by removal of the 5′-hydroxy (OH) group. Cyclic adenosine monophosphate (cAMP) is pervasive in signal transduction. Its derivatives include the energy carriers adenosine mono-, di-, and triphosphate, also known as AMP/ADP/ATP. Adenosine is one of the four nucleoside building blocks of RNA (and its derivative deoxyadenosine is a building block of DNA), which are essential for all life. The molecule consists of an adenine attached to a ribose via a β-N 9- glycosidic bond. Adenosine ( symbol A) is an organic compound that occurs widely in nature in the form of diverse derivatives.
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