Thiazide () refers to both a class of sulfur-containing organic molecules
Thiazide organic molecules are bi-cyclic structures that contain adjacent sulfur and nitrogen atoms on one ring.
Medical uses
Thiazide diuretics are primarily used to treat the
hypertension (high blood pressure) and
edema (swelling) caused by water overload as well as certain conditions related to unbalanced calcium metabolism.
Water balance
Hypertension
There are many causes of
hypertension (high blood pressure), including advancing age, smoking and
obesity.
Sometimes the underlying cause of hypertension cannot be determined, resulting in a diagnosis of idiopathic hypertension. Regardless of the cause, someone may have very high hypertension without any initial symptoms. Uncontrolled hypertension will eventually cause damage to the heart, kidneys and eyes. Lifestyle changes, including reducing dietary salt, increasing exercise and losing weight can help to reduce blood pressure.
Thiazides and thiazide-like diuretics have been in constant use since their introduction in 1958. Decades as a cornerstone of hypertension treatment show how well these drugs perform for most patients.
Clinical practice guidelines regarding the use of thiazides vary by geographic region. Guidelines in the United States recommend thiazides as a first-line treatment for hypertension (JNC VIII).[National Institute for Health and Clinical Excellence (NICE) guideline on the management of primary hypertension in adults (CG127) accessed 5/3/2012 at ] Thiazides have also been replaced by in Australia due to the association between thaizide use and increased risk of developing diabetes mellitus type 2.[Guide to management of hypertension 2008. National Heart Foundation Australia. 2008. accessed online at ]
Diabetes insipidus
Thiazides can be used to paradoxically decrease urine flow in people with nephrogenic diabetes insipidus.
Thiazides may also be useful in treating
hyponatremia (low blood sodium) in infants with central diabetes insipidus.
Calcium balance
Urinary stones
Thiazides are useful in treating
kidney stones and
bladder stones that result from
hypercalciuria (high urine calcium levels). Thiazides increase the uptake of calcium in the distal tubules, to moderately reduce urinary calcium. Thiazides combined with potassium citrate, increased water intake and decreased dietary
oxalate and sodium can slow or even reverse the formation of calcium-containing kidney stones.
High-dose therapy with the thiazide-like diuretic
indapamide can be used to treat idiopathic hypercalcinuria (high urine calcium with unknown cause).
Osteoporosis
Hypocalcemia (low blood calcium) can be caused by a variety of conditions that reduce dietary calcium absorption, increase calcium excretion or both. Positive calcium balance occurs when calcium excretion is decreased and intake remains constant so that calcium is retained within the body.
[Aung K, Htay T. Thiazide diuretics and the risk of hip fracture. Cochrane Database of Systematic Reviews 2011, Issue 10. Art. No.: CD005185. DOI: 10.1002/14651858.CD005185.pub2.] Higher levels of retained calcium are associated with increased bone mineral density and fewer fractures in individuals with
osteoporosis.
By a poorly understood mechanism, thiazides directly stimulate
osteoblast differentiation and bone mineral formation, further slowing the course of osteoporosis.
Dent's disease
Thiazides may be used to treat the symptoms of Dent's disease, an X-linked genetic condition that results in electrolyte imbalance with repeated episodes of kidney stones. A case study of two brothers with the condition, two years of treatment with hydrochlorothiazide reduced the incidence of kidney stones and improved kidney function.
The thiazide-like diuretic
chlortalidone reduced urine
calcium oxalate in seven of the eight males with inactivated CLCN5 gene that participated in the study.
Inactivation of the CLCN5 gene causes Dent's disease Type 1.
The rare nature of Dent's disease makes it difficult to coordinate large controlled studies, so most evidence for thiazide use is with too few patients to make broad recommendations possible.
Long-term thiazide use may not be advisable due to the risk of significant adverse side effects.
Other uses
Bromine intoxication can be treated by giving intravenous saline with either thiazides or
.
Contraindications
Contraindications include:
Thiazides reduce the clearance of uric acid since they compete for the same transporter, and therefore raise the levels of uric acid in the blood. Hence, they are prescribed with caution in patients with gout or hyperuricemia.
Chronic administration of thiazides is associated with the increase of insulin resistance which can lead to hyperglycemia.
Thiazides cause loss of blood potassium, while conserving blood calcium.
Thiazides can decrease placental perfusion and adversely affect the fetus, so should be avoided in pregnancy.
Adverse effects
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Hypokalemia – Thiazide diuretics reduce potassium concentration in blood through two indirect mechanisms: inhibition of sodium-chloride symporter at distal convoluted tubule of a nephron and stimulation of aldosterone that activates Na+/K+-ATPase at collecting duct. Inhibition of sodium-chloride symporter increases availability of sodium and chloride in urine. When the urine reaches the collecting duct, the increase in sodium and chloride availability activates Na+/K+-ATPase, which increases the absorption of sodium and excretion of potassium into the urine. Long term administration of thiazide diuretics reduces total body blood volume. This activates the renin–angiotensin system, stimulates the secretion of aldosterone, thus activating Na+/K+-ATPase, increasing excretion of potassium in urine.
-
Hyperglycemia
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Hyperlipidemia
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Hyperuricemia
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Hypercalcemia
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Hyponatremia
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According to a 2025 retrospective study patients who experience early hyponatremia after beginning thiazide diuretics have a higher risk of mortality compared to those with stable sodium levels.
-
Hypomagnesemia
-
Hypocalciuria
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Metabolic alkalosis
Mechanism of action
Thiazide diuretics control hypertension in part by inhibiting
reabsorption of
sodium (Na
+) and
chloride (Cl
−)
from the distal convoluted tubules in the
by blocking the thiazide-sensitive Na
+-Cl
− symporter.
The term "thiazide" is also often used for drugs with a similar action that do not have the thiazide chemical structure, such as
chlortalidone,
metolazone and
indapamide. These agents are more properly termed thiazide-like diuretic.
[ ]
Anyhow, the results regarding the importance of the kidney alone and the thiazide-sensitive receptor NCC Sodium-chloride symporter in the anti-hypertensive effects of thiazides have been debated for decades providing evidence for the existence of an extrarenal target involved in the thiazide-mediated chronic inhibition of vascular constriction. [ ]
The membrane-associated phospholipase NAPE-PLD (N-acyl phosphatidylethanolamine-specific phospholipase D) of the endocannabinoid system is a renal and extrarenal target of "thiazide-type" (e.g., hydrochlorothiazide) and "thiazide-like" diuretics (e.g., chlorthalidone and indapamide). NAPE-PLD accounts for both their acute (diuresis and accompanying decrease of plasma volume) and chronic (reduction of arterial pressure through vascular dilation) therapeutic effects.
Thiazide diuretics also increase calcium reabsorption at the distal tubule. By lowering the sodium concentration in the tubule epithelial cells, thiazides indirectly increase the activity of the basolateral Na+/Ca2+ antiporter to maintain intracellular Na+ level, facilitating Ca2+ to leave the epithelial cells into the renal interstitium. Thus, intracellular Ca2+ concentration is decreased, which allows more Ca2+ from the lumen of the tubules to enter epithelial cells via apical Ca2+-selective channels (TRPV5). In other words, less Ca2+ in the cell increases the driving force for reabsorption from the lumen.
Thiazides are also thought to increase the reabsorption of Ca2+ by a mechanism involving the reabsorption of sodium and calcium in the proximal tubule in response to sodium depletion. Some of this response is due to augmentation of the action of parathyroid hormone.
Breastfeeding
Thiazides pass into
breast milk and can decrease the flow of breast milk.
Thiazides have been associated with significant
in some nursing infants and should be administered to nursing mothers with caution.
History
The thiazide diuretics were developed by scientists Karl H. Beyer, James M. Sprague, John E. Baer, and Frederick C. Novello of Merck and Co. in the 1950s,
and led to the marketing of the first drug of this class,
chlorothiazide, under the trade name Diuril in 1958.
The research leading to the discovery of chlorothiazide, leading to "the saving of untold thousands of lives and the alleviation of the suffering of millions of victims of hypertension" was recognized by a special Public Health Award from the Lasker Foundation in 1975.
