Receptor blockers

Alfuzosin (91) is a prazosin-like hypotensive adrenergic a-1 receptor blocker with the special structural feature that two carbons have been excised conceptually from the piperazine ring normally present in this series. Following the usual sequence for this series, reaction of 4-amino-2-chloro-7-dimethoxyquinazoline (89) with the tetrahydro-2-furyl amide of 3-methylaminopropyla-mine (90) gives alfuzosin (91) [25], Alfuzosin is claimed to cause less orthostatic hypotention (dizziness or fainting upon sudden rising) than prazosin. 

VEGF receptor blockers Small receptor tyrosine kinase antagonists... 

Angiotensin-Converting Enzyme Inhlbltors/Anglotensln-Receptor Blockers... 

Nickenig G, Ostergren J, Struijker-Boudier H (2006) Clinical evidence for the cardiovascular benefits of angiotensin receptor blockers. JRAAS 7 (Suppl 1) S1-S7... 

A large number of diugs interfere with the smooth muscle contraction. These compounds lower blood pressure and are referred to as antihypertensive. In this section, only those coumpounds will be mentioned that have a direct effect on smooth muscle tone. Phenylephrine is an agonist on most smooth muscles and activates ax adrenoceptors. Carbachol is an agonist on some smooth muscles and activates contraction through muscarinic receptors. Blockers of the ax-adrenoceptors such as prazosin and urapidil are competitive inhibitors of the ax-receptor in vascular and bladder smooth muscle. Phenoxybenzamine is an ineversible blocker of ax receptors and phentol-amine blocks ax and a2 receptors. Ca2+ channel blockers such as the dihydropyiidines, phenylalkyla-mines and benzothiazepines lower smooth muscle tone by blocking the L-type calcium channel. 

Figure 8. Simultaneous measurement of intracellular Ca and oxidant production in neutrophils. Cells were labeled with Quin-2 and suspended at 2 x lo cells/mL buffer. At time zero, 1 nJf FLPEP was added (upper trace in each panel). In addition, the receptor blocker tBOC was added (3 x 10" M) after 30 s to stop further binding of the stimulus (lower trace in each panel). The excitation wavelength was 3A0 nm. Top panel Quin-2 fluorescence determined on channel B (of Figure 1) using a Corion A90-nm interference filter. The crossover from the superoxide assay has been subtracted. Middle panel Oxidant production (superoxide equivalents) determined by the para-hydroxyphenylacetate assay. Fluorescence was observed at AOO nm (on channel A of Figure 1).

MTX caused a contraction of vascular smooth muscle and positive inotropic, positive chronotropic and arrhythmogenic effects on cardiac muscle. The effect of MTX was little affected by various receptor blockers, a Na channel blocker or a catecholamine depleting agent. Further, MTX had no effect on the enzymes which were related to Ca movements, such as Na , K -ATPase, cyclic AMP phosphodiesterase, and sarcoplasmic reticulum Ca -ATPase. These results would eliminate the possible involvement of an indirect action elicited by the release of chemical mediators and direct modifications of their receptors, Na channels, or various enzymes as a major mechanism of action of MTX. 

DeWit, H., and Wise, R.A. Blockade of cocaine reinforcement in rats with the dopamine receptor blocker pimozide, but not with the noradrenergic blockers phentolamine and phenoxybenzamine. Can J Psychol 31 195-203, 1977. 

Other medications (e.g., angiotensin converting enzyme inhibitors, angiotensin receptor blockers, and diuretics)... 

ACE, angiotensin-converting enzyme ARB, angiotensin receptor blocker ... 

ACE-I, angiotensin-converting enzyme inhibitor Aid Ant, aldosterone antagonist ARB, angiotensin receptor blocker BB, beta-blocker CCBA, calcium channel blocking agent DirVaso, direct vasodilator. 

Angiotensin receptor blockers show similar tolerability to ACE inhibitors with regard to hypotension and hyperkalemia, but they do not induce cough since ARBs do not cause an accumulation of bradykinin. Angiotensin receptor blockers can be considered in patients with ACE inhibitor-induced angioedema, but they should be initiated cautiously, as crossreactivity has been reported. Many of the other considerations for the use of ARBs are similar to those of ACE inhibitors,... 

FIGURE 3-1. Treatment algorithm for chronic heart failure. ACE, angiotensin-converting enzyme ARB, angiotensin receptor blocker EF, ejection fraction HF, heart failure LV, left ventricular Ml, myocardial infarction SOB shortness of breath. Table 3-5 describes staging of heart failure. 

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