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Adenosine
Systematic (IUPAC) name
(2R,3R,4R,5R)-2-(6-aminopurin-9-yl)- 5-(hydroxymethyl)oxolane-3,4-diol
Identifiers
CAS number 58-61-7
ATC code C01EB10
PubChem 60961
DrugBank APRD00132
Chemical data
Formula C10H13N5O4 
Mol. mass 267. IUPAC Nomenclature is a system of naming Chemical compounds and of describing the science of Chemistry in general CAS registry numbers are unique numerical identifiers for Chemical compounds Polymers biological sequences mixtures and Alloys They are also referred to The Anatomical Therapeutic Chemical Classification System is used for the classification of drugs It is controlled by the WHO Collaborating Centre for Drug A section of the Anatomical Therapeutic Chemical Classification System. PubChem is a Database of chemical Molecules The system is maintained by the National Center for Biotechnology Information (NCBI a component The DrugBank database available at the University of Alberta is a unique Bioinformatics and Cheminformatics resource that combines detailed drug (i A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the The molecular mass (abbreviated m of a substance, more commonly referred to as molecular weight and abbreviated as MW, is the Mass of one 242 g/mol
SMILES eMolecules & PubChem
Pharmacokinetic data
Bioavailability Rapidly cleared from circulation via cellular uptake
Protein binding No
Metabolism Rapidly converted to inosine and adenosine monophosphate
Half life cleared plasma <30 seconds - half life <10 seconds
Excretion can leave cell intact or can be degraded to hypoxanthine, xanthine, and ultimately uric acid
Therapeutic considerations
Pregnancy cat.

C
Legal status

Australia - Legal; UK - Legal; US - Rx only
Routes IV or injection

Adenosine is a nucleoside composed of adenine attached to a ribose (ribofuranose) moiety via a β-N9-glycosidic bond. In Pharmacology, bioavailability is used to describe the fraction of an administered Dose of unchanged drug that reaches the Systemic circulation, one of A drug's efficiency may be affected by the degree to which it binds to the proteins within Blood plasma. Drug metabolism is the Metabolism of drugs, their Biochemical modification or degradation usually through specialized enzymatic systems The biological half-life of a substance is the time it takes for a substance (drug radioactive nuclide or other to lose half of its pharmacologic physiologic or radiologic activity Excretion is the process of eliminating waste products of Metabolism and other non-useful materials The pregnancy category of a pharmaceutical agent is an assessment of the risk of fetal injury due to the pharmaceutical if it is used as directed by the mother during The regulation of therapeutic goods, that is drugs and therapeutic devices, varies by jurisdiction In Pharmacology and Toxicology, a route See also Adenosine triphosphate (ATP Adenine is a Purine with a variety of roles in Biochemistry including Cellular respiration, in the form of both the energy-rich Adenosine Ribose (ɹˈaɪbəʊs ɹˈaɪbəɹʊs primarily seen as D-ribose, is an Aldopentose — a Monosaccharide containing five Carbon Ribofuranose is the biochemical name for the 5- Carbon Sugar ( Pentose) commonly known as Ribose when having the Furan ring structure In Chemistry, a glycosidic bond is a certain type of Functional group that joins a Carbohydrate (sugar molecule to another which may be another carbohydrate

Adenosine plays an important role in biochemical processes, such as energy transfer - as adenosine triphosphate (ATP) and adenosine diphosphate (ADP) - as well as in signal transduction as cyclic adenosine monophosphate, cAMP. Biochemistry is the study of the chemical processes in living Organisms It deals with the Structure and function of cellular components such as Adenosine-5'-triphosphate ( ATP) is a multifunctional Nucleotide that is most important as a " molecular currency" of intracellular Energy Adenosine diphosphate, abbreviated ADP, is a Nucleotide. It is an Ester of Pyrophosphoric acid with the Nucleoside Adenosine In Biology, signal transduction refers to any process by which a cell converts one kind of signal or stimulus into another Cyclic adenosine monophosphate ( cAMP, cyclic AMP or 3'-5'-cyclic Adenosine monophosphate) is a Second messenger that is important in many biological It is also an inhibitory neurotransmitter, believed to play a role in promoting sleep and suppressing arousal, with levels increasing with each hour an organism is awake.

Contents

Pharmacological effects

Adenosine is an endogenous purine nucleoside that modulates many physiologic processes. Cellular signaling by adenosine occurs through four known adenosine receptor subtypes (A1, A2A, A2B, and A3).

Extracellular adenosine concentrations from normal cells are approximately 300 nM; however, in response to cellular damage (e. g. in inflammatory or ischemic tissue), these concentrations are quickly elevated (600-1,200 nM). Thus, in regards to stress or injury, the function of adenosine is primarily that of cytoprotection preventing tissue damage during instances of hypoxia, ischemia, and seizure activity. Chronic Hypoxia is a pathological condition in which the body as a whole ( generalized hypoxia) or region of the body ( tissue hypoxia) is deprived of adequate In Medicine, ischemia ( Greek ισχαιμία, isch- is restriction hema or haema is Blood) is a restriction Activation of A2A receptors produces a constellation of responses that in general can be classified as anti-inflammatory.

Adenosine receptors

Main article: Adenosine receptor

The different adenosine receptor subtypes (A1, A2A, A2B, and A3) are all seven transmembrane spanning G-protein coupled receptors. The adenosine receptors (or P1 receptors) are a class of Purinergic receptors, G-protein coupled receptors with Adenosine as Endogenous G protein-coupled receptors ( GPCRs) also known as seven transmembrane domain receptors, 7TM receptors, heptahelical receptors, and These four receptor subtypes are further classified based on their ability to either stimulate or inhibit adenylate cyclase activity. Adenylate cyclase ( also known as adenylyl cyclase or AC) is a Lyase Enzyme. The A2A and A2B receptors couple to Gάs and mediate the stimulation of adenylate cyclase, while the A1 and A3 adenosine receptors couple to Gάi which inhibits adenylate cyclase activity. Additionally, A1 receptors couple to Gάo, which has been reported to mediate adenosine inhibition of Ca2+ conductance, whereas A2B and A3 receptors also couple to Gάq and stimulate phospholipase activity.

Anti-inflammatory Properties

Adenosine is a potent anti-inflammatory agent, acting at its four G-protein coupled receptors. Topical treatment of adenosine to foot wounds in diabetes mellitus has been shown in lab animals to drastically increase tissue repair and reconstruction. Diabetes mellitus (ˌdaɪəˈbiːtiːz or /ˌdaɪəˈbiːtəs/ /məˈlaɪtəs/ or /ˈmɛlətəs/ often referred to simply as diabetes ( Ancient Greek: grc Topical administration of adenosine for use in wound healing deficiencies and diabetes mellitus in humans is currently under clinical investigation.

Action on the heart

When administered intravenously, adenosine causes transient heart block in the AV node. A heart block is a disease in the electrical system of the Heart. The atrioventricular node (abbreviated AV node) is an area of specialized tissue between the atria and the ventricles of the Heart, specifically This is mediated via the A1 receptor, inhibiting adenyl cyclase, reducing cAMP and so causing cell hyperpolarization by increasing outward K+ flux. The adenosine A1 receptor is one member of the Adenosine receptor group of G protein-coupled receptors with Adenosine as Endogenous It also causes endothelial dependent relaxation of smooth muscle as is found inside the artery walls. This causes dilatation of the "normal" segments of arteries, i. e. where the endothelium is not separated from the tunica media by atherosclerotic plaque. The endothelium is the thin layer of cells that line the interior surface of Blood vessels forming an interface between circulating Blood in the In Pathology, an atheroma (plural atheromata is an accumulation and swelling (-oma in Artery walls that is made up of cells (mostly Macrophage cells This feature allows physicians to use adenosine to test for blockages in the coronary arteries, by exaggerating the difference between the normal and abnormal segments.

In individuals suspected of suffering from a supraventricular tachycardia (SVT), adenosine is used to help identify the rhythm. A supraventricular tachycardia ( SVT) is a rapid rhythm of the Heart in which the origin of the electrical signal is either the atria or Certain SVTs can be successfully terminated with adenosine. This includes any re-entrant arrhythmias that require the AV node for the re-entry (e. Dysrhythmia redirects here For the American band see Dysrhythmia (band. g. , AV reentrant tachycardia (AVRT), AV nodal reentrant tachycardia (AVNRT). AV nodal reentrant tachycardia ( AVNRT) is a type of Tachycardia (fast rhythm of the Heart. In addition, atrial tachycardia can sometimes be terminated with adenosine.

Adenosine has an indirect effect on atrial tissue causing a shortening of the refractory period. When administered via a central lumen catheter, adenosine has been shown to initiate atrial fibrillation because of its effect on atrial tissue. Atrial fibrillation ( AF or afib) is a Cardiac arrhythmia (abnormal heart rhythm that involves the two upper chambers ( atria) of the Heart In individuals with accessory pathways, the onset of atrial fibrillation can lead to a life threatening ventricular fibrillation. Ventricular fibrillation ( V-fib or VF) is a condition in which there is uncoordinated contraction of the Cardiac muscle of the ventricles in the

Fast rhythms of the heart that are confined to the atria (e. In Anatomy, the atrium (plural atria) refers to a chamber or space g. , atrial fibrillation, atrial flutter) or ventricles (e. Atrial fibrillation ( AF or afib) is a Cardiac arrhythmia (abnormal heart rhythm that involves the two upper chambers ( atria) of the Heart Atrial flutter is an abnormal heart rhythm that occurs in the atria of the Heart. In the Heart, a ventricle is a heart chamber which collects Blood from an atrium (another heart chamber that is smaller than a ventricle and g. , monomorphic ventricular tachycardia) and do not involve the AV node as part of the re-entrant circuit are not typically converted by adenosine. Ventricular tachycardia ( V-tach or VT) is a Tachycardia, or fast heart rhythm that originates in one of the ventricles of the Heart However, the ventricular response rate is temporarily slowed with adenosine in such cases.

Because of the effects of adenosine on AV node-dependent SVTs, adenosine is considered a class V antiarrhythmic agent. Antiarrhythmic agents are a group of Pharmaceuticals that are used to suppress fast rhythms of the Heart ( Cardiac arrhythmias) such as Atrial fibrillation When adenosine is used to cardiovert an abnormal rhythm, it is normal for the heart to enter ventricular asystole for a few seconds. Synchronized electrical cardioversion is the process by which an abnormally fast Heart rate or Cardiac arrhythmia is terminated by the delivery of a therapeutic dose In medicine asystole is a state of no cardiac electrical activity hence no contractions of the Myocardium and no cardiac output or blood flow This can be disconcerting to a normally conscious patient, and is associated with angina-like sensations in the chest. [1]

Caffeine's principal mode of action is as an antagonist of adenosine receptors in the brain. They are presented here side by side for comparison.
Caffeine's principal mode of action is as an antagonist of adenosine receptors in the brain. Caffeine is a bitter white crystalline Xanthine Alkaloid that acts as a Psychoactive Stimulant Drug and a mild Diuretic A receptor antagonist is a type of receptor ligand or Drug that does not provoke a biological response itself upon binding to a receptor, but blocks They are presented here side by side for comparison.

By nature of caffeine's purine structure it binds to some of the same receptors as adenosine. Caffeine is a bitter white crystalline Xanthine Alkaloid that acts as a Psychoactive Stimulant Drug and a mild Diuretic Purine ( 1) is a heterocyclic Aromatic Organic compound, consisting of a Pyrimidine ring fused to an Imidazole ring The pharmacological effects of adenosine may therefore be blunted in individuals who are taking large quantities of methylxanthines (e. Xanthine (ˈzænθiːn ˈzænθaɪn] (37-dihydro-purine-26-dione is a Purine base found in most body tissues and fluids and in other organisms g. , caffeine, found in coffee and tea, or theobromine, as found in chocolate). Caffeine is a bitter white crystalline Xanthine Alkaloid that acts as a Psychoactive Stimulant Drug and a mild Diuretic Theobromine, also known as xantheose, which also includes the similar compounds Theophylline and Caffeine.

Action in CNS

Generalized, adenosine has an inhibitory effect in the central nervous system (CNS). In Vertebrates the central nervous system ( CNS) is the part of the Nervous system which is enclosed in the Meninges. Caffeine's stimulatory effects, on the other hand, are primarily (although not entirely) credited to its inhibition of adenosine by binding to the same receptors, and therefore effectively blocking adenosine receptors in the CNS. This reduction in adenosine activity leads to increased activity of the neurotransmitters dopamine and glutamate. See Chemical synapse for an introduction to concepts and terminology used in this article Dopamine is a Hormone and Neurotransmitter occurring in a wide variety of animals including both vertebrates and invertebrates Glutamic acid (abbreviated as Glu or E) is one of the 20 Alpha Amino acids It is not among the human Essential amino acids Its

Dosage

When given for the evaluation or treatment of an SVT, the initial dose is 6 mg, given as a fast IV/IO push. Intravenous therapy or IV therapy is the giving of Liquid substances directly into a Vein. Intraosseous infusion is the process of injection directly into the Marrow of the bone Due to adenosine's extremely short half-life, the IV line is started as proximal to the heart as possible, such as the antecubital fossa. The IV push is often followed with an immediate flush of 5-10ccs of saline. If this has no effect (e. g. , no evidence of transient AV block), a 12mg dose can be given 1-2 minutes after the first dose. If the 12mg dose has no effect, a second 12mg dose can be administered 1-2 minutes after the previous dose. Some clinicians may prefer to administer a higher dose (typically 18 mg), rather than repeat a dose that apparently had no effect. 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 who are presenting Congestive Heart Failure, Myocardial Infarction, shock, hypoxia, and/or hepatic or renal insufficiency, and in elderly patients. Heart failure is a Cardiac condition that occurs when a problem with the structure or function of the Heart impairs its ability to supply Myocardial infarction ( MI or AMI for acute myocardial infarction) also known as a heart attack, occurs when the blood supply Chronic Hypoxia is a pathological condition in which the body as a whole ( generalized hypoxia) or region of the body ( tissue hypoxia) is deprived of adequate Old age consists of ages nearing or surpassing the Average life span of Human beings and thus the end of the human life cycle.

Drug Interactions

Dopamine may precipitate toxicity in the patient. Carbamazepine may increase heart block. Theophylline and caffeine (methylxanthines) antagonize adenosine's effects; may require increased dose of adenosine.

Contraindications

Contraindications for adenosine are e. In Medicine, a contraindication (pronounced as contra-indication is a condition or factor that increases the Risks involved in using a particular drug, g. :

In Wolf-Parkinson-White syndrome adenosine may be administered if equipment for cardioversion is immediately available as a backup.

Side effects

Many individuals experience facial flushing, lightheadedness, asystole, diaphoresis, or nausea after administration of adenosine. In medicine asystole is a state of no cardiac electrical activity hence no contractions of the Myocardium and no cardiac output or blood flow Diaphoresis is excessive sweating commonly associated with shock and other Medical emergency conditions These symptoms are transitory, usually lasting less than one minute.

Metabolism

When adenosine enters the circulation, it is broken down by adenosine deaminase, which is present in red cells and the vessel wall. Red blood cells are the most common type of Blood cell and the Vertebrate body's principal means of delivering Oxygen to the body tissues via the Blood

Dipyridamole, an inhibitor of adenosine deaminase, allows adenosine to accumulate in the blood stream. Dipyridamole is a drug that inhibits thrombus formation when given chronically and causes Vasodilation when given at high doses over short time Adenosine deaminase (also known as ADA) is an Enzyme ( involved in purine metabolism. This causes an increase in coronary vasodilatation.

See also

References

  1. ^ Pijls, Nico H. The adenosine receptors (or P1 receptors) are a class of Purinergic receptors, G-protein coupled receptors with Adenosine as Endogenous J. ; Bernard De Bruyne (2000). Coronary Pressure. Springer. ISBN 0792361709.  

External links


Dictionary

adenosine

-noun

  1. (biochemistry, genetics, uncountable) A nucleoside derived from adenine and ribose, found in striated muscle tissue.
  2. (countable, chemistry) An instance of adenosine.
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