Adenosine is a naturally occurring organic compound that is important to the biochemistry of living organisms, including humans. It also helps to regulate arousal and sleep and protect cells from damage. Additionally, it is a component of several larger, related molecules with important functions such as intracellular messaging and providing energy for metabolism. In medicine, it is also sometimes given intravenously to treat heart conditions. Its chemical formula is C10H13N5O4.
It is a type of chemical called a purine nucleoside, a term describing its molecular structure. Purine compounds are composed of two linked ring-shaped structures of atoms called aromatic rings, which have unusually high chemical stability. A nucleoside is a compound in which a compound called a nucleobase, or simply a base, is bonded with a molecule of either ribose (C5H10O5) or deoxyribose (C5H10O4), both of which are simple sugars or monosaccharides. Adenosine consist of ribose combined with the purine adenine (C5H5N5).
The amount of the substance in the body gradually increases during waking hours. Due to its inhibitory effect on the nervous system, this eventually begins to cause drowsiness and finally sleep, at which point the amount of the chemical in the body starts dropping again. Part of the reason for the effectiveness of caffeine (C8H10N4O2) as a stimulant is that caffeine can bind to the same receptors in cells and so interferes with the normal effects of high adenosine levels. Adenosine levels in the bloodstream also increase significantly in areas suffering from inflammation or restricted blood or oxygen supply, where the chemical helps to decrease inflammation and prevent cell damage.
Several important chemicals in the body are composed of adenosine combined with one or more phosphate groups. Adenosine monophosphate (C10H14N5O7P) is a type of chemical called a second messenger, which transmits chemical messages from the exterior of his cell to the interior. Adenosine triphosphate (C10H16N5O13P3), or ATP, is an important source of chemical energy for the body and powers many metabolic processes with the energy released when its chemical bonds break down. Adenosine diphosphate (C10H15N5O10P2) is produced by the breakdown of ATP and can be recycled to produce more ATP with the energy produced from food in animals or photosynthesis in plants.
It also has medical uses. When injected into the bloodstream, it slows the heart rate due to its electrical effects on the atrioventricular node, which regulates heartbeat, and inhibit the release of the neurotransmitter norepinephrine. It also causes the smooth muscle tissue around arteries to relax and dilate. Adenosine is used by doctors to identify artery blockages or abnormalities in heartbeat. It can also be an effective treatment for some cases of abnormally accelerated heartbeat, or tachycardia.
Adenosine is a chemical that is present in all human cells. It readily combines with phosphate to form various chemical compounds including adenosine monophosphate (AMP) and adenosine triphosphate (ATP). People use it for medicine.
AMP is taken by mouth for treating shingles (herpes zoster infection) and a blood disorder called porphyria cutanea tarda.
ATP is used under the tongue to increase physical energy. It is also given intravenously (by IV) for treating acute kidney failure, multiple organ failure, high blood pressure in lung arteries (pulmonary hypertension), cystic fibrosis, lung cancer, weight loss associated with cancer, and controlling blood pressure during anesthesia and surgery. It is also used for cardiac stress tests.
Healthcare providers give adenosine intravenously for treating surgical pain and nerve pain, pulmonary hypertension, and certain types of irregular heartbeat. It is also given for controlling blood pressure during anesthesia and surgery and for heart tests called cardiac stress tests.
Adenosine is injected into the space around the spinal cord to treat nerve pain.
Adenosine phosphate is given by injection into the muscle (intramuscularly) for treating varicose veins, bursitis, pain and swollen tendons (tendonitis), itchiness, multiple sclerosis (MS), neuropathy, shingles (herpes zoster infection), cold sores and genital herpes (herpes simplex infections), and poor blood circulation.
Adenosine is believed to be an anti-inflammatory agent at the A(2A) receptor. Topical treatment of adenosine to foot wounds in diabetes mellitus has been shown in lab animals to drastically increase tissue repair and reconstruction. Topical administration of adenosine for use in wound healing deficiencies and diabetes mellitus in humans is currently under clinical investigation.
Methotrexate's anti-inflammatory effect may be due to its stimulation of adenosine release.
When administered intravenously, adenosine causes transient heart block in the Atrioventricular (AV) node. This is mediated via the A1 receptor, inhibiting adenylyl cyclase, reducing cAMP and so causing cell hyperpolarization by increasing outward K+ flux. It also causes endothelial dependent relaxation of smooth muscle as is found inside the artery walls. This causes dilation of the "normal" segments of arteries; i.e. where the endothelium is not separated from the tunica media by atherosclerotic plaque. 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. Certain SVTs can be successfully terminated with adenosine. This includes any re-entrant arrhythmias that require the AV node for the re-entry, e.g., AV reentrant tachycardia (AVRT), AV nodal reentrant tachycardia (AVNRT). In addition, atrial tachycardia can sometimes be terminated with adenosine.
Because of the effects of adenosine on AV node-dependent SVTs, adenosine is considered a class IV 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.
Generalized, adenosine has an inhibitory effect in the central nervous system (CNS). 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.
Adenosine blocks faulty circuitry in the heart, which causes irregular heart rhythm. Adenosine triphosphate (ATP) might prevent changes in energy metabolism that cause weight loss in people with advanced cancer.
Many individuals experience facial flushing, a temporary rash on the chest, lightheadedness, diaphoresis, or nausea after administration of adenosine due to its vasodilatory effects. Metallic taste is a hallmark side effect of adenosine administration. These symptoms are transitory, usually lasting less than one minute. It is classically associated with a sense of "impending doom", more prosaically described as apprehension. This lasts a few seconds after administration of a bolus dose, during transient asystole induced by intravenous administration. In some cases adenosine can make patients' limbs feel numb for about 2–5 minutes after administration intravenously depending on the dosage (usually above 12 mg).
Not enough is known about the use of adenosine during pregnancy and breast-feeding. Stay on the safe side and avoid use.
Brand Names: Adenocard, Adenoscan
Please note - some side effects for Adenosine may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.
All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Adenosine:
Chest pressure; dizziness; flushing of the face; headache; lightheadedness; nausea; tingling in the arms.
Seek medical attention right away if any of these SEVERE side effects occur when using Adenosine:
Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); chest pain; fast, slow, or irregular heartbeat; seizure; shortness of breath or wheezing.
This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider. Call your doctor for medical advice about side effects. To report side effects to the appropriate agency, please read the Guide to Reporting Problems to FDA.