Blood volume antihypertensives increasing

Many antihypertensive drug lower the blood pressure by dilating or increasing the size of the arterial blood vessels (vasodilatation). Vasodilatation creates an increase in the lumen (the space or opening within an arteiy) of the arterial blood vessels, which in turn increases the amount of space available for the blood to circulate Because blood volume (the amount of blood) remains relatively constant, an increase in the space in which the blood circulates (ie, the blood vessels) lowers the pressure of the fluid (measured as blood pressure) in the blood vessels. Although the method by which anti-hypertensive drug dilate blood vessels varies, the result... 

The chief use of reserpine is in the treatment of mild to moderate hypertension. As with other sympathetic depressant drugs, tolerance to the antihypertensive effects of reserpine can occur, owing to a compensatory increase in blood volume that frequently accompanies decreased peripheral vascular resistance. Reserpine, therefore, should be used in conjunction with a diuretic. 

An antihypertensive substance is one which does not affect blood volume, blood viscosity, or the function of the heart it lowers blood pressure to normal levels in hypertensive states by generalized arteriolar dilatation, including those of the kidneys. Vasodilators (such as histamine), which lower arterial pressure at the expense of renal blood flow, are not antihypertensive. Furthermore, an ideal substance should affect the blood pressure in normal states to little or no extent. It can be predicted, however, that when true antihypertensive substances are found, they will not increase or maintain renal blood flow in the face of lowered arterial pressure when renal arterioles have lost the ability to dilate because of pathological changes (see Figure 3). 

The molecular mechanism of diuretics acting as antihypertensive agents is not completely clear however, use of diuretics causes a significant increase in the amount of water and electrolytes excreted in urine, which leads to a reduction in the volume of extracellular fluid and plasma. This in turn leads to a reduction of cardiac output, which is the main parameter responsible for a drop in arterial blood pressure and venous blood return. Cardiac output is gradually restored, but the hypotensive effect remains, possibly because of the reduced peripheral resistance of vessels. It is also possible that diuretics somehow lower vascular activity of noradrenaline and other factors of pressure in the organism. Methods of synthesizing thiazide diuretics used for hypertension are described in the preceding chapter. Chapter 21. 

Diuretics increase the formation and excretion of urine. These drugs are used as antihypertensive agents because of their ability to increase the renal excretion of water and sodium, thus decreasing the volume of fluid within the vascular system. This situation is somewhat analogous to the decrease in pressure that would occur inside a balloon if some of the air inside were allowed to leak out. Consequently, diuretics appear to have a rather direct effect on blood pressure... 

Diuretics are highly efficient drugs for the treatment of edema associated with congestive heart failure. They are also used to increase the volume of urine excreted by the kidneys [9]. For example, duranide, 81, a dichlorinated benzene disulfonamide, is an oral carbonic anhydrase inhibitor. Duranide reduces intraocular pressure by partially suppressing the secretion of aqueous humor [11]. Diuril, 82, has an antihypertensive activity and is issued to control blood pressure [9]. Edecrin, 83, is an unsaturated ketone derivative of an aryloxyacetic acid. Edecrin is used in the treatment of the edema associated with congestive heart failure, renal disease, and cirrhosis of the liver [11]. Amiloride, 84, is also used as an adjunctive treatment with thiazide diuretics in congestive heart failure hypertension. 

Patients with normal left ventricular function will not have an increase in stroke volume when SVR falls because the normal ventricle is fairly insensitive to small changes in afterload. Consequently, these patients experience a significant decrease in blood pressure after administration of arterial vasodilators. This explains why nitroprusside is a potent antihypertensive agent in patients without heart failure but causes less hypotension and reflex tachycardia in patients with left ventricular dysfunction. Nonetheless, even a modest increase in heart rate could have adverse consequences in patients with underlying ischemic heart disease and/or resting tachycardia, and close monitoring is necessary during therapy. 

Diazoxide is a parenteral, rapid, and direct-acting vasodilating antihypertensive used in hypertensive emergencies. An IV injection can drop blood pressure by as much as 80 mmHg in 5 minutes. Unlike sodium nitroprusside, however, venous dilation is not part of its mechanism. Chemically it is a benzothiadiazide without the sulfamoyl function at the 7 position (see diuretics). In fact, diazoxide is not a diuretic. Chronic use of diazoxide reflexly increases renin release, which actually counteracts the antihypertensive effect of the drug by expanding the volume of circulating fluid. 

Diuretics have an antihypertensive effect by promoting sodium and water loss. They block sodium and chloride reabsorption causing a decrease in fluid volume, a lowering of blood pressure, and a decrease of edema. If sodium is retained, water is also retained in the body and blood pressure increases. 

A diuretic is a compound that causes increased urination and thereby reduces fluid volume in the body. An important use of diuretics in clinical medicine is in the reduction of the fluid buildup, particularly in the lungs, that is associated with congestive heart failure. It is also used as an antihypertensive (i.e., to reduce blood pressure). Furosemide, an exceptionally potent diuretic, is prescribed under 30 or more trade... 

Diuretics are used to increase the volume of urine excreted by the kidneys. They are effective in the treatment of edema associated with congestive heart failure. The thiazide diuretics (e.g., hydrochlorothiazide) have antihypertensive activity and are used to control blood pressure either alone or in combination with other antihypertensive agents. Spironolactone (an aldosterone antagonist) and amiloride are potassium-sparing diuretics. 

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