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Benzothiadiazine, the parent structure of this class of molecules
Chlorothiazide, the first thiazide drug

Thiazide (/ˈθəzd/) is a type of molecule[1] and a class of diuretics[2] often used to treat hypertension (high blood pressure) and edema (such as that caused by heart failure, liver failure, or kidney failure).

The thiazides and thiazide-like diuretics reduce the risk of death, stroke, heart attack, and heart failure due to hypertension.[3] The class was discovered and developed at Merck and Co. in the 1950s, and the first approved drug of this class, chlorothiazide, was marketed under the trade name Diuril beginning in 1958.[4] In most countries, the thiazides are the least expensive antihypertensive drugs available.[5]


Medical usesEdit


Regarding effectiveness in the treatment of hypertension, a systematic review by the Cochrane Collaboration found:[6]

  • Chlorthalidone reduces systolic and diastolic blood pressure by 12.0/4.0 mmHg and the reduction is not dose related when tested at a range of doses from 12.5 mg to 75 mg/day.
  • Hydrochlorothiazide's effect is dose related and at a maximum dose of 50 mg/day, the reduction is 11/5 mmHg.

Thiazides and thiazide-like diuretics have been in constant use since their introduction in 1958. They "have remained a cornerstone in the management of hypertension for more than half a century since their introduction [...] Very few agents used for the treatment of any disease can boast such staying power, which is a testament both to the efficacy and safety of these compounds." [7]

Several clinical practice guidelines address the use of thiazides. They are the recommended first-line treatment in the US (JNC VIII)[8] guidelines for hypertension and a recommended treatment in the European (ESC/ESH)[9] guidelines. However, the recent 2011 UK National Institute for Health and Clinical Excellence (NICE) guideline on the management of primary hypertension in adults (CG127)[10] recommend an angiotensin-converting enzyme (ACE) inhibitor or calcium channel blockers (CCBs) as first line agents in hypertension and advise that thiazide-like diuretics should only be used first line if ACEis or CCBs are not suitable or if the patient has oedema or has a high risk of developing heart failure. Thiazides have also been replaced by angiotensin converting enzyme (ACE) inhibitors in Australia due to their propensity to increase risk of diabetes mellitus type 2.[11]

The mechanism of action of thiazides in lowering blood pressure in the long term is not fully understood. When administered acutely, thiazides lower blood pressure by causing diuresis, a fall in plasma volume and a reduction in cardiac output. However, after chronic use, thiazides cause a reduction in blood pressure by lowering peripheral resistance (i.e. vasodilation). The mechanism of this effect is uncertain, but it may involve effects on 'whole body' or renal autoregulation, or direct vasodilator actions either through inhibition of carbonic anhydrase[12] or by desensitizing the vascular smooth muscle cells to the rise in intracellular calcium induced by norepinephrine.[13]


Thiazides also lower urinary calcium excretion, making them useful in preventing calcium-containing kidney stones. This effect is associated with positive calcium balance and is associated with an increase in bone mineral density and reductions in fracture rates attributable to osteoporosis.[14] By a lesser understood mechanism, thiazides directly stimulate osteoblast differentiation and bone mineral formation, further slowing the course of osteoporosis.[15]

Because of their promotion of calcium retention, thiazides are used in the treatment of


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.[16][17]

Chronic administration is associated with 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.[17][18]

Adverse effectsEdit

Mechanism of actionEdit

The members of this class of diuretics are derived from benzothiadiazine. They control hypertension in part by inhibiting reabsorption of sodium (Na+) and chloride (Cl) ions from the distal convoluted tubules in the kidneys by blocking the thiazide-sensitive Na+-Cl symporter.[20] The term "thiazide" is also often used for drugs with a similar action that do not have the thiazide chemical structure, such as chlorthalidone and metolazone. These agents are more properly termed thiazide-like diuretics.

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.[21]

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.[22]


Thiazide refers to both the type of molecule[23] and the medication.[24] This can lead to confusion, because some molecules (thiazide-like diuretics) are often considered as thiazide diuretics, although they are not thiazides from a chemical perspective. In this context, "thiazide" refers to a drug which acts at a "thiazide receptor",[25] which is a sodium-chloride symporter.

Breast milkEdit

Thiazides pass into breast milk, and can decrease the flow of breast milk.[26] Thiazides are classed as 'Drugs That Have Been Associated With Significant Effects on Some Nursing Infants and Should Be Given to Nursing Mothers With Caution' by the American Academy of Pediatrics Committee on Drugs.[27]


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,[4] and led to the marketing of the first drug of this class, chlorothiazide, under the trade name Diuril in 1958.[28] 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.[29]


  1. ^ Thiazides at the US National Library of Medicine Medical Subject Headings (MeSH)
  2. ^ Thiazide+Diuretics at the US National Library of Medicine Medical Subject Headings (MeSH)
  3. ^ Wright JM, Musini VM, Gill R (April 2018). "First-line drugs for hypertension". The Cochrane Database of Systematic Reviews. 4: CD001841. doi:10.1002/14651858.CD001841.pub3. PMC 6513559. PMID 29667175.
  4. ^ a b Beyer KH (September 1993). "Chlorothiazide. How the thiazides evolved as antihypertensive therapy". Hypertension. 22 (3): 388–91. doi:10.1161/01.hyp.22.3.388. PMID 8349332.
  5. ^ Whitworth JA (November 2003). "2003 World Health Organization (WHO)/International Society of Hypertension (ISH) statement on management of hypertension" (PDF). Journal of Hypertension. 21 (11): 1983–92. doi:10.1097/00004872-200311000-00002. PMID 14597836.
  6. ^ Musini VM, Nazer M, Bassett K, Wright JM (May 2014). "Blood pressure-lowering efficacy of monotherapy with thiazide diuretics for primary hypertension". The Cochrane Database of Systematic Reviews. 5 (5): CD003824. doi:10.1002/14651858.CD003824.pub2. PMID 24869750.
  7. ^ Moser M, Feig PU (November 2009). "Fifty years of thiazide diuretic therapy for hypertension". Archives of Internal Medicine. JAMA. 169 (20): 1851–6. doi:10.1001/archinternmed.2009.342. PMID 19901136.
  8. ^ James PA, Oparil S, Carter BL, Cushman WC, Dennison-Himmelfarb C, Handler J, et al. (February 2014). "2014 evidence-based guideline for the management of high blood pressure in adults: report from the panel members appointed to the Eighth Joint National Committee (JNC 8)". JAMA. 311 (5): 507–20. doi:10.1001/jama.2013.284427. PMID 24352797.
  9. ^ "". Archived from the original on 2008-05-17. Retrieved 2007-08-30.
  10. ^ National Institute for Health and Clinical Excellence (NICE) guideline on the management of primary hypertension in adults (CG127) accessed 5/3/2012 at "Archived copy". Archived from the original on 2012-01-31. Retrieved 2012-03-05.CS1 maint: Archived copy as title (link)
  11. ^ Guide to management of hypertension 2008. National Heart Foundation Australia. 2008. accessed online at "Archived copy" (PDF). Archived from the original (PDF) on 2013-05-15. Retrieved 2013-07-10.CS1 maint: Archived copy as title (link)
  12. ^ Hughes AD (December 2004). "How do thiazide and thiazide-like diuretics lower blood pressure?". Journal of the Renin-Angiotensin-Aldosterone System. 5 (4): 155–60. doi:10.3317/jraas.2004.034. PMID 15803433.
  13. ^ Zhu Z, Zhu S, Liu D, Cao T, Wang L, Tepel M (February 2005). "Thiazide-like diuretics attenuate agonist-induced vasoconstriction by calcium desensitization linked to Rho kinase". Hypertension. 45 (2): 233–9. doi:10.1161/01.HYP.0000152701.97426.5f. PMID 15611360.
  14. ^ 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.
  15. ^ Dvorak MM, De Joussineau C, Carter DH, Pisitkun T, Knepper MA, Gamba G, Kemp PJ, Riccardi D (September 2007). "Thiazide diuretics directly induce osteoblast differentiation and mineralized nodule formation by interacting with a sodium chloride co-transporter in bone". Journal of the American Society of Nephrology. 18 (9): 2509–16. doi:10.1681/ASN.2007030348. PMC 2216427. PMID 17656470.
  16. ^
  17. ^ a b "Archived copy". Archived from the original on 2010-10-09. Retrieved 2010-05-14.CS1 maint: Archived copy as title (link)
  18. ^ "Hypertension in Pregnancy - Gynecology and Obstetrics".
  19. ^ Dowd, Frank J; Johnson, Bart; Mariotti, Angelo (3 September 2016). Pharmacology and Therapeutics for Dentistry - E-Book. Elsevier Health Sciences. pp. 324–326. ISBN 9780323445955. Retrieved 4 November 2017.
  20. ^ Duarte JD, Cooper-DeHoff RM (June 2010). "Mechanisms for blood pressure lowering and metabolic effects of thiazide and thiazide-like diuretics". Expert Review of Cardiovascular Therapy. 8 (6): 793–802. doi:10.1586/erc.10.27. PMC 2904515. PMID 20528637.
  21. ^ Longo, Dan L; et al. (2012). Harrison's Principals of Internal Medicine, Vol. 2. New York: McGraw-Hill. p. 2285. ISBN 978-0-07-174887-2.
  22. ^ Longo, Dan L; et al. (2012). Harrison's Principals of Internal Medicine, Vol. 2. New York: McGraw-Hill. p. 3109. ISBN 978-0-07-174887-2.
  23. ^ Thiazides at the US National Library of Medicine Medical Subject Headings (MeSH)
  24. ^ Thiazide+Diuretics at the US National Library of Medicine Medical Subject Headings (MeSH)
  25. ^ thiazide+receptor at the US National Library of Medicine Medical Subject Headings (MeSH)
  26. ^ Gerald G. Briggs; Roger K. Freeman; Sumner J. Yaffe (2011). Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk. Lippincott Williams & Wilkins. pp. 257–. ISBN 978-1-60831-708-0.
  27. ^ "Transfer of drugs and other chemicals into human milk". Pediatrics. 108 (3): 776–89. September 2001. doi:10.1542/peds.108.3.776. PMID 11533352.
  28. ^ "Drugs@FDA: FDA Approved Drug Products".
  29. ^ "The Lasker Foundation - Awards".

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