Regadenoson (Lexiscan), a low affinity agonist of the A2A adenosine receptor, increases coronary blood flow (CBF) and mimics the increase in CBF caused by exercise. Myocardial uptake of the radiopharmaceutical is proportional to CBF creating the contrast required to identify stenotic coronary arteries. It is a pharmacologic stress agent indicated for radionuclide myocardial perfusion imaging (MPI) in patients unable to undergo adequate exercise stress. The most common adverse reactions to Lexiscan are dyspnea, headache, flushing, chest discomfort, dizziness, angina pectoris, chest pain, and nausea. Methylxanthines, e.g., caffeine and theophylline, may interfere with the activity of Lexiscan. Aminophylline may be used to attenuate severe and/or persistent adverse reactions to Lexiscan.

Adenosine is a nucleoside that is composed of adenine and d-ribose, occurring in all cells of the body and play many important biological roles in addition to being components of DNA and RNA. Adenosine itself is a neurotransmitter. Adenocard (adenosine injection) is used as an initial treatment for the termination of paroxysmal supraventricular tachycardia (PVST), including that associated with accessory bypass tracts (Wolff-Parkinson-White Syndrome). When clinically advisable, appropriate vagal maneuvers. Adenocard does not convert atrial flutter, atrial fibrillation, or ventricular tachycardia to normal sinus rhythm. In the presence of atrial flutter or atrial fibrillation, a transient modest slowing of ventricular response may occur immediately following Adenocard administration. Adenosine slows conduction time through the A-V node, can interrupt the reentry pathways through the A-V node, and can restore normal sinus rhythm. This effect may be mediated through the drug's activation of cell-surface A1 and A2 adenosine receptors. Adenocard is antagonized competitively by methylxanthines such as caffeine and theophylline, and potentiated by blockers of nucleoside transport such as dipyridamole. Adenocard is not blocked by atropine. Adenosine also inhibits the slow inward calcium current and activation of adenylate cyclase in smooth muscle cells, thereby causing relaxation of vascular smooth muscle. By increasing blood flow in normal coronary arteries with little or no increase in stenotic arteries, adenosine produces a relative difference in thallous (thallium) chloride TI 201 uptake in myocardium supplied by normal verus stenotic coronary arteries.

Regadenoson (Lexiscan), a low affinity agonist of the A2A adenosine receptor, increases coronary blood flow (CBF) and mimics the increase in CBF caused by exercise. Myocardial uptake of the radiopharmaceutical is proportional to CBF creating the contrast required to identify stenotic coronary arteries. It is a pharmacologic stress agent indicated for radionuclide myocardial perfusion imaging (MPI) in patients unable to undergo adequate exercise stress. The most common adverse reactions to Lexiscan are dyspnea, headache, flushing, chest discomfort, dizziness, angina pectoris, chest pain, and nausea. Methylxanthines, e.g., caffeine and theophylline, may interfere with the activity of Lexiscan. Aminophylline may be used to attenuate severe and/or persistent adverse reactions to Lexiscan.

Adenosine monophosphate (AMP) is a nucleotide, consisting of a phosphate group, the sugar ribose, and the nucleobase adenine. AMP is an activator of several enzymes in the tissues. In the glycolytic pathway, the enzyme phosphofructokinase is inhibited by ATP but the inhibition is reversed by AMP, the deciding factor for the reaction being the ratio between ATP and AMP. In medicine, AMP is used mainly as an alternative to adenosine for treatment of ischemia and as a tool compound to measure hyperresponsiveness of airways.

Adenosine monophosphate (AMP) is a nucleotide, consisting of a phosphate group, the sugar ribose, and the nucleobase adenine. AMP is an activator of several enzymes in the tissues. In the glycolytic pathway, the enzyme phosphofructokinase is inhibited by ATP but the inhibition is reversed by AMP, the deciding factor for the reaction being the ratio between ATP and AMP. In medicine, AMP is used mainly as an alternative to adenosine for treatment of ischemia and as a tool compound to measure hyperresponsiveness of airways.

Adenosine triphosphate (ATP) is an adenine nucleotide containing three phosphate groups esterified to the sugar moiety. Adenosine triphosphate is the energy source in living cells. In physiological conditions, the average concentration varies from 3150 mM in mammalian cells to 1500–1900 mM in human blood cells. Extracellular adenosine and adenosine triphosphate (ATP) are involved in biological processes including neurotransmission, muscle contraction, cardiac function, platelet function, vasodilatation, signal transduction and secretion in a variety of cell types. A large family of membrane-bound receptors mediates cell signalling by ATP and adenosine. These purinergic receptors ultimately determine the variety of effects induced by extracellular ATP and adenosine. ATP and adenosine have strong negative chronotropic and dromotropic effects on the mammalian heart. The sensitivity of the sinus node and the atrioventricular node to ATP and adenosine manifests pronounced variability among species. For more than three decades, ATP has been used routinely in Europe in the acute therapy of paroxysmal supraventricular tachycardia. ATPace™, an injectable formulation of adenosine 5′-triphosphate (ATP), was developed by Cordex Pharma, Inc. (Cordex) as a diagnostic and therapeutic drug for the management of cardiac bradyarrhythmias. Extracellular ATP exerts multiple effects in various cell types by activating cell-surface receptors known as P2 receptors. In the heart, ATP suppresses the automaticity of cardiac pacemakers and atrioventricular (AV) nodal conduction via adenosine, the product of its degradation by ecto-enzymes, as well as by triggering a cardio-cardiac vagal reflex. ATP, given as a rapid intravenous bolus injection, has been used since the late 1940s as a highly effective and safe therapeutic agent for the acute termination of reentrant paroxysmal supraventricular tachycardia (PSVT) involving the AV node. In addition, preliminary studies have shown that ATP can also be used as a diagnostic agent for the identification of several cardiac disorders including sinus node dysfunction (sick sinus syndrome), dual AV nodal pathways, long QT syndrome, and bradycardic syncope. The US Food and Drug Administration has approved Cordex formulation for ATP as an Investigational New Drug and two pathways for its marketing approval; one therapeutic, i.e., acute termination of paroxysmal PSVT, and the other diagnostic, i.e., the identification of patients with bradycardic syncope who can benefit from pacemaker therapy. However later ATPace development for the treatment of bradycardia and paroxysmal supraventricular tachycardia was discontinued.

Clamoxyquin is an antiamebic and antidiarrheal agent. Clamoxyquin is usually used as the pamoate or hydrochloride salt. It is a veterinary antiparasitic drug used to treat salmonids for the myxozoan parasite Myxobolus cerebralis. Dietary inclusion of several anti-coccidial drugs, including clamoxyquin, proguanil and fumagillin, has been found effective against myxozoan infections in finfish.