An aquaretic is a class of drug that is used to promote aquaresis

Aquaresis

Aquaresis is the excretion of water without electrolyte loss. It is preferable to diuresis in the treatment of hyponatremia....

. They are not strictly speaking diuretic

Diuretic

A diuretic provides a means of forced diuresis which elevates the rate of urination. There are several categories of diuretics. All diuretics increase the excretion of water from bodies, although each class does so in a distinct way.- Medical uses :...

s, but are sometimes classified as such.

Pharmacokinetics

These increase blood flow to the kidney

Kidney

The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...

s without increasing sodium

Sodium

Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...

 and chloride

Chloride

The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...

 resorption

Resorption

Resorption is a process by which a structure is remodeled.Types include:* Bone resorption* Root resorption...

, thus causing an increase in urine whilst retaining electrolytes. However, the increase in intravascular

Blood vessel

The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...

 fluid volume that they cause translates into an increase vascular

Blood vessel

The blood vessels are the part of the circulatory system that transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...

 resistance, and higher blood pressure

Blood pressure

Blood pressure is the pressure exerted by circulating blood upon the walls of blood vessels, and is one of the principal vital signs. When used without further specification, "blood pressure" usually refers to the arterial pressure of the systemic circulation. During each heartbeat, BP varies...

.

Chemical constitutents

Synthetic aquaretics, a new class of drug, are V2 receptor antagonist

Antagonist

An antagonist is a character, group of characters, or institution, that represents the opposition against which the protagonist must contend...

s, such as OPC-31260. Additional examples include conivaptan

Conivaptan

Conivaptan is a non-peptide inhibitor of antidiuretic hormone . It was approved in 2004 for hyponatremia caused by syndrome of inappropriate antidiuretic hormone , and there is some evidence it may be effective in heart failure...

, demeclocycline

Demeclocycline

Demeclocycline is a tetracycline antibiotic.It is derived from a strain of Streptomyces aureofaciens.-In infections:...

, and lithium

Lithium

Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...

. These have been used in clinical trials as a treatment for Syndrome of inappropriate antidiuretic hormone

Syndrome of inappropriate antidiuretic hormone

The syndrome of inappropriate antidiuretic hormone hypersecretion is characterized by excessive release of antidiuretic hormone from the posterior pituitary gland or another source. The result is hyponatremia and sometimes fluid overload...

(SIADH).