Different types of diuretics
Diuretics increase the urinary elimination of electrolytes, in particular of sodium. All have an antihypertensive effect through the decrease of the peripheral vascular resistance resulting from sodium depletion by increase of its urinary elimination. Some of them could, moreover, reduce directly the intracellular sodium concentration in vascular smooth muscles by modifying the ion exchanges at the level of their plasma membranes.
The decrease of intracellular sodium tends to reduce the intracellular calcium concentration because in compensation the exchanger Na+/Ca2+ introduces sodium in the cell, which implicates calcium efflux.
The decrease of the arterial pressure is thus not usually the consequence of a decrease of the circulating blood mass, or hypovolemia, secondary to an aqueous diuresis.
An aqueous depletion can be however observed, at least transitorily, with certain very effective diuretics like furosemide, especially when they are used by parenteral route for the treatment of congestive heart failure, acute pulmonary edema for example.
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