Blood flow agents

The meta-orientation of the two methoxyl groups does, however, greatly increase the susceptibility of the aromatic ring to electrophilic attack. This is one of the three possible meta-dimethoxy substituted amphetamines, and it is the best studied one in the pursuit of potential radio-halogen substituted brain blood-flow agents. This strategy is discussed under 1DNNA the other two meta-compounds are discussed under 3,4-DMA. 

In the area of psychedelic drugs, the value of 2,5-DMA is mainly in its role as a precursor to the preparation of materials that can come from a direct electrophilic attack on the activated 4-position. These uses can be found under things such as DOB and DOI and DON. The radio-halogenation of N-substituted homologues of 2,5-DMA with hypoiodite or hypofluorite is part of an extensive study undenway in the search for radio-labeled brain blood flow agents. The... 

Brain imaging is stiU an active field of research in radiopharmaceutical chemistry. The compounds for brain imaging can be divided into two classes, one of which is discussed in this section. For the evaluation of the brain, one can apply either regional blood flow agents or receptor specific agents. Currently, the only Food and Drug Administration (FDA)-approved Tc radiopharmaceuticals are from the first class, so-called perfusion agents, but substantial efforts for the introduction of radiopharmaceuticals of the second class are currendy... 

Some P-adrenoceptor blockers have intrinsic sympathomimetic activity (ISA) or partial agonist activity (PAA). They activate P-adrenoceptors before blocking them. Theoretically, patients taking P-adrenoceptor blockers with ISA should not have cold extremities because the dmg produces minimal decreases in peripheral blood flow (smaller increases in resistance). In addition, these agents should produce minimal depression of heart rate and cardiac output, either at rest or during exercise (36). 

Propranolol. Propranolol (Table 1), a Class II antiarrhythmic agent, is usefiil in the management of hypertrophic subaortic stenosis, especially for the treatment of exertional or other stress-induced angina by improving blood flow. The dmg can increase exercise tolerance in patients suffering from angina. Propranolol has been shown to have cardioprotective action in post-MI patients (37—39,98,99,108). 

P-Adrenoceptor Blockers. There is no satisfactory mechanism to explain the antihypertensive activity of P-adrenoceptor blockers (see Table 1) in humans particularly after chronic treatment (228,231—233). Reductions in heart rate correlate well with decreases in blood pressure and this may be an important mechanism. Other proposed mechanisms include reduction in PRA, reduction in cardiac output, and a central action. However, pindolol produces an antihypertensive effect without lowering PRA. In long-term treatment, the cardiac output is restored despite the decrease in arterial blood pressure and total peripheral resistance. Atenolol (Table 1), which does not penetrate into the brain is an efficacious antihypertensive agent. In short-term treatment, the blood flow to most organs (except the brain) is reduced and the total peripheral resistance may increase. 

The success of thrombus lysis depends mainly on how large the thrombus is and whether any blood flow stiU remains. The outcome is better the larger the surface of the entire thrombus exposed to the thrombolytic agent. As the clot ages, the polymerization of fibria cross-linking and other blood materials iacreases and it becomes more resistant to lysis. Therefore, the eadier the thrombolysis therapy starts, the higher the frequency of clot dissolution. Thrombolytic agents available are Hsted ia Table 7 (261—276). 

The phthalazine ring system has yielded a pair of quite effective antihypertensive agents. Both these drugs are believed to act as vasodilators they would owe much of their effectiveness to the consequent decrease in resistance to blood flow in the periphery. Condensation of the half-aldehyde corresponding... 

As to be expected from a peptide that has been highly conserved during evolution, NPY has many effects, e.g. in the central and peripheral nervous system, in the cardiovascular, metabolic and reproductive system. Central effects include a potent stimulation of food intake and appetite control [2], anxiolytic effects, anti-seizure activity and various forms of neuroendocrine modulation. In the central and peripheral nervous system NPY receptors (mostly Y2 subtype) mediate prejunctional inhibition of neurotransmitter release. In the periphery NPY is a potent direct vasoconstrictor, and it potentiates vasoconstriction by other agents (mostly via Yi receptors) despite reductions of renal blood flow, NPY enhances diuresis and natriuresis. NPY can inhibit pancreatic insulin release and inhibit lipolysis in adipocytes. It also can regulate gut motility and gastrointestinal and renal epithelial secretion. 

The proposal that NO or its reactant products mediate toxicity in the brain remains controversial in part because of the use of non-selective agents such as those listed above that block NO formation in neuronal, glial, and vascular compartments. Nevertheless, a major area of research has been into the potential role of NO in neuronal excitotoxicity. Functional deficits following cerebral ischaemia are consistently reduced by blockers of NOS and in mutant mice deficient in NOS activity, infarct volumes were significantly smaller one to three days after cerebral artery occlusion, and the neurological deficits were less than those in normal mice. Changes in blood flow or vascular anatomy did not account for these differences. By contrast, infarct size in the mutant became larger... 

Agent Fibrin Specificity TIMI-3 Blood Flow Complete Perfusion at 90 Minutes Systemic Bleeding Risk/ICH Risk Administration Average Wholesale Price3 Other Approved Uses... 

Only non-selective p-blockers reduce bleeding complications in patients with known varices. Blockade of P, receptors reduces cardiac output and splanchnic blood flow. 02-Adrenergic blockade prevents p2-receptor-mediated splanchnic vasodilation while allowing unopposed a-adrenergic effects this enhances vasoconstriction of both the systemic and splanchnic vascular beds. The combination of P, and P2 effects makes the non-selective p-blockers preferable to car-dioselective agents in treating portal hypertension.1,36,41... 

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