adenosine

[ah-den´o-sēn]

1. a nucleoside composed of the pentose sugar d-ribose and adenine. It is a structural subunit of ribonucleic acid (RNA). Adenosine nucleotides are involved in the energy metabolism of all cells. Adenosine can be linked to a chain of one, two, or three phosphate groups to form adenosine monophosphate (AMP), adenosine diphosphate (ADP), or adenosine triphosphate (ATP). The bond between the phosphate groups in ADP or the two bonds between phosphate groups in ATP are called high-energy bonds, because hydrolysis of a high-energy bond provides a large amount of free energy that can be used to drive other processes that would not otherwise occur. The energy that is derived from the breakdown of carbohydrates, fats, or proteins is used to synthesize ATP. The energy stored in ATP is then used directly or indirectly to drive all other cellular processes that require energy, of which there are four major types: (1) the transport of molecules and ions across cell membranes against concentration gradients, which maintains the internal environment of the cell and produces the membrane potential for the conduction of nerve impulses; (2) the contraction of muscle fibers and other fibers producing the motion of cells; (3) the synthesis of chemical compounds; (4) the synthesis of other high-energy compounds.

Adenosine.

2. a preparation of adenosine, which acts as a cardiac depressant of automaticity in the sinus node and conduction in the atrioventricular node and as a vasodilator. It is used as an antiarrhythmic and is also used to cause coronary vasodilation during myocardial perfusion imaging in patients who cannot exercise adequately to perform an exercise stress test, administered intravenously.

cyclic adenosine monophosphate a cyclic nucleotide, adenosine 3′,5′-cyclic monophosphate, involved in the action of many hormones, including catecholamines, ACTH, and vasopressin. The hormone binds to a specific receptor on the cell membrane of target cells. This activates an enzyme, adenylate cyclase, which produces cyclic AMP from ATP. Cyclic AMP acts as a second messenger activating other enzymes within the cell. Abbreviated 3′,5′-AMP, cAMP, and cyclic AMP.

adenosine diphosphate (ADP) a nucleotide, adenosine 5′-pyrophosphate, produced by the hydrolysis of adenosine triphosphate (ATP). It is then converted back to ATP by the metabolic processes oxidative phosphorylation, glycolysis, and the tricarboxylic acid cycle.

adenosine monophosphate (AMP) a nucleotide, adenosine 5′-phosphate, involved in energy metabolism and nucleotide synthesis. Called also adenylic acid.

adenosine triphosphatase (ATPase) a term used to refer to the enzymatic activity of certain intercellular processes that split ATP to form ADP and inorganic phosphate, when the energy released is not used for the synthesis of chemical compounds. Examples are the splitting of ATP in muscle contraction and the transport of ions across cell membranes.

adenosine triphosphate (ATP) a nucleotide, adenosine 5′-triphosphate, occurring in all cells, where it stores energy in the form of high-energy phosphate bonds. Free energy is supplied to drive metabolic reactions, to transport molecules against concentration gradients (active transport), and to produce mechanical motion (contraction of myofibrils and microtubules), when ATP is hydrolyzed to ADP and inorganic phosphate or to AMP and inorganic pyrophosphate. ATP is also used to produce high-energy phosphorylated intermediary metabolites, such as glucose 6-phosphate.

adenosine

Adenacor (UK), Adenocard, Adenoscan

Pharmacologic class: Endogenous nucleoside

Therapeutic class: Antiarrhythmic

Pregnancy risk category C

Action

Converts paroxysmal supraventricular tachycardia (PSVT) to normal sinus rhythm by slowing conduction through atrioventricular (AV) node and interrupting reentry pathway. Also used as a diagnostic agent in thallium scanning.

Availability

Injection: 3 mg/ml

Indications and dosages

Adenocard-

➣ PSVT, including that associated with Wolff-Parkinson-White syndrome (after attempting vagal maneuvers, when appropriate)

Adults and children weighing more than 50 kg (110 lb): Initially, 6 mg by rapid I.V. bolus over 1 to 2 seconds. If desired effect isn't achieved within 1 to 2 minutes, give 12 mg by rapid I.V. bolus; may repeat 12-mg I.V. bolus dose as needed. Maximum single dosage is 12 mg.

Children weighing less than 50 kg (110 lb): 0.05 to 0.1 mg/kg by rapid I.V. bolus. If this dosage proves ineffective, increase in 1 to 2 minutes by 0.05 mg/kg q 2 minutes, to a maximum single dosage of 0.3 mg/kg. Maximum single dosage is 12 mg.

Adenoscan-

➣ Diagnosis of coronary artery disease in conjunction with thallium-201 myocardial perfusion scintigraphy in patients unable to exercise adequately during testing

Adults: 140 mcg/kg/minute by I.V. infusion over 6 minutes, for a total dosage of 0.84 mg/kg. Required dose of thallium-201 is injected at midpoint (after first 3 minutes) of Adenoscan infusion.

Off-label uses

• Diagnosis of supraventricular arrhythmias

• Pulmonary hypertension

Contraindications

• Hypersensitivity to drug

• Second- or third-degree AV block

• Sinus node disease

• Bronchoconstrictive lung disease

Precautions

Use cautiously in:

• asthma, angina

• elderly patients

• pregnant patients

• children.

Administration

• Don't administer through central line (may cause asystole).

• Don't give more than 12 mg Adenocard as a single dose.

• Don't dilute Adenocard. Administer Adenocard by I.V. injection as a rapid bolus directly into vein whenever possible during cardiac monitoring.

• After administering Adenocard, flush I.V. line immediately and rapidly with normal saline solution to drive drug into bloodstream.

• Dilute a single dose of Adenoscan in sufficient normal saline solution to be given by continuous infusion over 6 minutes.

Adverse reactions

CNS: light-headedness, dizziness, apprehension, headache, tingling in arms, numbness

CV: chest pain, palpitations, hypotension, ST-segment depression, first- or second-degree AV block, atrial tachyarrhythmias, other arrhythmias

EENT: blurred vision, tightness in throat

GI: nausea, pressure in groin

Musculoskeletal: discomfort in neck, jaw, and arms

Respiratory: chest pressure, dyspnea and urge to breathe deeply, hyperventilation

Skin: burning sensation, facial flushing, sweating

Other: metallic taste

Interactions

Drug-drug. Carbamazepine: worsening of progressive heart block

Digoxin, verapamil: increased risk of ventricular fibrillation

Dipyridamole: increased adenosine effect

Theophylline: decreased adenosine effect

Drug-food. Caffeine: decreased adenosine effect

Drug-herbs. Aloe, buckthorn bark or berry, cascara sagrada, rhubarb root, senna leaf or fruits: increased adenosine effect

Guarana: decreased adenosine effect

Drug-behaviors. Smoking: increased risk of tachycardia

Patient monitoring

• Monitor heart rhythm for new arrhythmias after administering dose.

• Check vital signs. Assess for chest pain or pressure, dyspnea, and sweating.

☞ Watch for bronchoconstriction in patients with asthma, emphysema, or bronchitis.

• Ask patient if he has recently used aloe, buckthorn, cascara sagrada, guarana, rhubarb root, or senna. If response is positive, notify prescriber.

Patient teaching

• Advise patient to report problems at infusion site.

• Tell patient he may experience 1 to 2 minutes of flushing, chest pain and pressure, and breathing difficulty during administration. Assure him that these effects will subside quickly.

• Advise patient to minimize GI upset by eating small, frequent servings of healthy food and drinking plenty of fluids.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, foods, herbs, and behaviors mentioned above.

a·den·o·sine (Ado),

(ă-den'ō-sēn),

A condensation product of adenine and d-ribose; a nucleoside found among the hydrolysis products of nucleic acids and of the various adenine nucleotides, including ATP; adenosine accumulates in severe combined immunodeficiency disease; a potent coronary vasod ilator used in place of exercise for radionuclide myocardial perfusion studies.

Synonym(s): 9-β-d-ribofuranosyladenine

adenosine

(ə-dĕn′ə-sēn′)

A nucleoside, C₁₀H₁₃N₅O₄, composed of adenine linked to ribose, that is a component of nucleic acids and of ADP, AMP, and ATP, and that plays a role in regulating various physiological functions.

Adenosine

An endogenous nucleoside composed of adenine linked to d-ribose, which results from the hydrolysis of adenylic acid. Adenosine is a therapeutic alternative to verapamil, in treating both narrow- and wide-complex paroxysmal supraventricular tachycardia (SVT). Adenosine reduces heart rate, followed by a reflex increase in sinus discharge. It has been regarded by some workers as the agent of choice to acutely terminate SVTs for AV nodal or AV reentry tachycardias.

adenosine

Cardiology An endogenous nucleoside composed of adenine linked to d-ribose, which results from the hydrolysis of adenylic acid; adenosine is a therapeutic alternative to verapamil, in treating both narrow- and wide-complex SVT; it ↓ heart rate, followed by a reflex ↑ in sinus discharge. See Calcium-channel blocker, Supraventricular tachycardia.

a·den·o·sine

(Ado) (ă-den'ō-sēn)

1. A condensation product of adenine and d-ribose; a nucleoside found among the hydrolysis products of all nucleic acids and of the various adenine nucleotides.

2. A potent coronary vasodilator used in place of exercise for radionuclide myocardial perfusion studies.
Synonym(s): gamma (γ)-beta (β)-d-ribofuranosyladenine.

adenosine

A purine NUCLEOSIDE consisting of one molecule of adenine and one molecule of d-ribose. It is formed in the body by the enzymatic breakdown of adenosine triphosphate (ATP). Adenosine is a NEUROTRANSMITTER, a HORMONE, and a NEUROMODULATOR. It is also a potent blocking agent for the atrioventricular node of the heart and is used by injection as a drug to correct irregularities in the action of the heart. A brand name is Adenocor.

adenosine

a nitrogen-containing compound consisting of an ADENINEM base attached to a ribose sugar. Adenosine forms part of NUCLEOTIDES making up NUCLEIC ACIDS and ATP.

a·den·o·sine

(ă-den'ō-sēn)

Condensation product of adenine and d-ribose.