Adenosine
Adenosine (symbol A) is an organic compound that occurs widely in nature in the form of diverse derivatives. The molecule consists of an adenine attached to a ribose via a β-N9-glycosidic bond. 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 on Earth. Its derivatives include the energy carriers adenosine mono-, di-, and triphosphate, also known as AMP/ADP/ATP. Cyclic adenosine monophosphate (cAMP) is pervasive in signal transduction. Adenosine is used as an intravenous medication for some cardiac arrhythmias.
Not to be confused with adenine.Clinical data
Adenocard; Adenocor; Adenic; Adenoco; Adeno-Jec; Adenoscan; Adenosin; Adrekar; Krenosin
SR-96225 (developmental code name)
- C
(adenosine may be safe to the fetus in pregnant women)
Intravenous
- In general: ℞ (Prescription only)
Rapidly cleared from circulation via cellular uptake
No
Rapidly converted to inosine and adenosine monophosphate
cleared plasma <30 seconds; half-life <10 seconds
can leave cell intact or can be degraded to hypoxanthine, xanthine, and ultimately uric acid
C10H13N5O4
267.245 g·mol−1
Adenosyl (abbreviated Ado or 5'-dAdo) is the chemical group formed by removal of the 5′-hydroxy (OH) group. It is found in adenosylcobalamin (an active form of vitamin B12[1]) and as a radical in the radical SAM enzymes.[2]
Medical uses[edit]
Supraventricular tachycardia[edit]
In individuals with supraventricular tachycardia (SVT), adenosine is used to help identify and convert the rhythm.[3][4][5]
Certain SVTs can be successfully terminated with adenosine.[6] 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). In addition, atrial tachycardia can sometimes be terminated with adenosine.[7]
Fast 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. However, the ventricular response rate is temporarily slowed with adenosine in such cases.[7]
Because of the effects of adenosine on AV node-dependent SVTs, adenosine is considered a class V antiarrhythmic agent. When adenosine is used to cardiovert an abnormal rhythm, it is normal for the heart to enter ventricular asystole for a few seconds. This can be disconcerting to a normally conscious patient, and is associated with angina-like sensations in the chest.[8]
Nuclear stress test[edit]
Adenosine 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.[9]
Dosage[edit]
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,[10] given as a rapid parenteral infusion. 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. The IV push is often followed with a flush of 10–20 mL of normal saline. 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. 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.
The recommended dose may be increased in patients on theophylline since methylxanthines prevent binding of adenosine at receptor sites. The dose is often decreased in patients on dipyridamole (Persantine) and diazepam (Valium) because adenosine potentiates the effects of these drugs. 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.
Common contraindications for adenosine include
Metabolism[edit]
Adenosine used as a second messenger can be the result of de novo purine biosynthesis via adenosine monophosphate (AMP), though it is possible other pathways exist.[27]
When adenosine enters the circulation, it is broken down by adenosine deaminase, which is present in red blood cells and the vessel wall.
Dipyridamole, an inhibitor of adenosine nucleoside transporter, allows adenosine to accumulate in the blood stream. This causes an increase in coronary vasodilatation.
Adenosine deaminase deficiency is a known cause of immunodeficiency.
Vasodilation[edit]
It also plays a role in regulation of blood flow to various organs through vasodilation.[43][44][45]