Mercurial diuretics are a form of renal 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 :...

 containing mercury.

Although previously widely used, they have largely been superseded by safer diuretics such as thiazide

Thiazide

Thiazide is a term used to describe a type of molecule and a class of diuretics often used to treat hypertension and edema ....

s, and are hardly used anymore.

History and mechanism

Inorganic mercury

Mercury (element)

Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...

 compounds, such as mercury(I)chloride (calomel), were found to have diuretic properties when they were used to treat syphilis

Syphilis

Syphilis is a sexually transmitted infection caused by the spirochete bacterium Treponema pallidum subspecies pallidum. The primary route of transmission is through sexual contact; however, it may also be transmitted from mother to fetus during pregnancy or at birth, resulting in congenital syphilis...

. Proposed use of these compounds date back at least to the 16th century, shortly after the beginning of the syphilis epidemic in 1497 following Colombus' return to Europe.

Mercurial diuretics cause diuresis by reducing the reabsorption 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...

 in the ascending loop of Henle

Loop of Henle

In the kidney, the loop of Henle is the portion of a nephron that leads from the proximal convoluted tubule to the distal convoluted tubule. Named after its discoverer F. G. J...

, thus causing more water being delivered to the distal convoluted tubule

Distal convoluted tubule

The distal convoluted tubule is a portion of kidney nephron between the loop of Henle and the collecting duct system.- Physiology :It is partly responsible for the regulation of potassium, sodium, calcium, and pH...

. Unfortunately, earlier physicians misconstrued hallmark symptoms of mercury poisoning such as excessive salivation as signs of mercury's efficacy, including up until the early 1960s when the use of mercurial diuretics were halted in medicine.

Side effects

Due to the idiosyncratic nature of mercury toxicity, the risk of severe disease and sudden death are unpredictable and frequently show no warning signs. Physicians during the 20th century believed that a fever/rash complex suggested the risk of severe side effects for the next upcoming doses if treatment was not halted. Warkany and Hubbard (1953) noted in their seminal paper establishing mercury as the cause of infantile acrodynia that "... in modern times the capricious behavior of mercurial diuretics has been rather disturbing to those who use them frequently. Thousands of injections are given without untoward effects but occasionally a therapeutic dose results in sudden death. Only rarely is this caused by the first dose. More often the patient tolerates several - in one case 164 - doses before the fatal reaction occurs. The mechanism of these reactions is not clear: they can neither be explained nor predicted; yet they cannot be denied."

After finding associations between mercurial diuretics and "mercurial" nephrotic syndrome, in addition to the sharp decline in infantile acrodynia cases after the late 1950s following the removal of many sources of childhood mercury exposure, the dangers of mercurial diuretics were realized. This led to the discontinuation of mercurial diuretics in favor of far less toxic and far more effective diuretics. This is similar to the fashion in which penicillin quickly replaced mercurials, particularly calomel, in the late 1930s as the main antibiotic used in medicine for both children and adults.

Examples

Some common organic mercurials:

• Mersalyl acid
  Mersalyl acid
  Mersalyl acid is a mercurial diuretic. It is only rarely used, having been superseded by diuretic medications that do not contain mercury and are therefore less toxic....
  
   (Mersal) (Salyrgan)
• Meralluride
  Meralluride
  Meralluride is a mercurial diuretic....
  
  
• Mercaptomerin
• Mercurophylline
• Merethoxylline procaine