II. Indications

III. Dosing: Hypertension (Adults)

  1. Start: 12.5 to 25 mg orally daily
  2. Maximum: 50 mg/day
    1. Higher doses worsen Hypokalemia without additional Antihypertensive benefit

IV. Efficacy

  1. May be preferred over Hydrochlorothiazide
    1. Longer half life than immediate release Hydrochlorothiazide
    2. Two to three times as potent as Hydrochlorothiazide
      1. Chlorthalidone lowers systolic Blood Pressure 10 mmHg more than Hydrochlorothiazide
    3. However, 2022 study shows similar cardiovascular outcomes with Hydrochlorothiazide
      1. Ishani (2022) N Engl J Med 387(26):2401-10 +PMID: 36516076 [PubMed]
  2. Chlorthalidone is more likely to result in Hypokalemia (see below)
  3. Conversion: Use 12.5 mg of Chlorthalidone in place of 25 mg Hydrochlorothiazide

V. Precautions

  1. Monitor Serum Potassium at baseline, 2 weeks and every 6-12 months (increased Hypokalemia risk)
  2. Decrease Sodium intake
    1. High Sodium intake is associated with increased Potassium losses
    2. Also associated with worse Blood Pressure control)
  3. Consider Potassium Supplementation
    1. Avoid if on Potassium sparing agents or significant Chronic Kidney Disease
    2. Potassium chloride 20 meq orally daily for Hypokalemia or prevention of Hypokalemia or
    3. Dietary Potassium for prevention of Hypokalemia
  4. Consider using Chlorthalidone in combination with agents balance Potassium losses
    1. Additional Blood Pressure lowering required
      1. ACE Inhibitor or Angiotensin Receptor Blocker
      2. Spironolactone or Eplerenone
    2. No additional Blood Pressure lowering required
      1. Triamterene or Amiloride

VI. Pharmacokinetics

  1. Onset of activity: 2 hours
  2. Duration >24 hours

VII. Mechanism

VIII. Adverse Effects

IX. Safety

  1. Pregnancy Category B
    1. Pregnancy Category D if used for Pregnancy Induced Hypertension
  2. Unknown Safety in Lactation

XI. References

  1. (2012) Presc Lett 19(2): 8
  2. (2014) Presc Lett 21(9): 52
  3. (2021) Presc Lett, Resource #370507, Commonly Used Diuretics
  4. (2020) Med Lett Drugs Ther 62(1598): 73-80
  5. Olson (2020) Clinical Pharmacology, Medmaster Miami, p. 62-3
  6. Hamilton (2020) Tarascon Pocket Pharmacopoeia

Images: Related links to external sites (from Bing)

Related Studies

Cost: Medications

chlorthalidone (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing)
CHLORTHALIDONE 25 MG TABLET Generic $0.11 each
CHLORTHALIDONE 50 MG TABLET Generic $0.14 each

Ontology: Chlorthalidone (C0008294)

Definition (NCI) A long acting thiazide-like diuretic of the sulfamoylbenzamide class and is devoid of the benzothiadiazine structure. Chlorthalidone directly inhibits sodium and chloride reabsorption on the luminal membrane of the early segment in the distal convoluted tubule (DCT) in the kidney. This leads to an increase in sodium, chloride, bicarbonate, and potassium secretion resulting in the excretion of water. In addition, this agent, like other thiazide diuretics, decreases calcium and uric acid secretion. In addition, this agent inhibits many carbonic anhydrase (CA) isoenzymes. Chlorthalidone is used in the treatment of high blood pressure, edema and congestive heart failure. The elimination half-life is about 40 to 50 hours.
Definition (MSH) A benzenesulfonamide-phthalimidine that tautomerizes to a BENZOPHENONES form. It is considered a thiazide-like diuretic.
Concepts Pharmacologic Substance (T121) , Organic Chemical (T109)
MSH D002752
SnomedCT 387324004, 57893000
LNC LP16077-7, MTHU006890
English Chlorphthalidolone, Chlorthalidone, Oxodoline, Phthalamudine, Benzenesulfonamide, 2-chloro-5-(2,3-dihydro-1-hydroxy-3-oxo-1H-isoindol-1-yl)-, Chlortalidone, Benzenesulfonamide, 2-Chloro-5-(2,3-dihydro-1-hydroxy-3-oxo-1H-isoindol-1-yl)-, Benzenesulfonamide, 2-chloro-5-(1-hydroxy-3-oxo-1-isoindolinyl)-, chlorthalidone, chlorthalidone (medication), CHLORTHALIDONE, Chlorthalidone [Chemical/Ingredient], chlortalidone, Chlorthalidone (product), Chlorthalidone (substance)
Swedish Klortalidon
Czech chlorthalidon
Finnish Klooritalidoni
French Phthalamudine, Chlorthalidone, Chlortalidone
Russian KHLORTALIDON, FTALAMUDIN, KHLORFTALIDOLON, ФТАЛАМУДИН, ХЛОРТАЛИДОН, ХЛОРФТАЛИДОЛОН
Japanese クロルサリドン, クロルフタリドロン, フタルアムジン, クロルタリドン
Croatian KLORTALIDON
Polish Chlortalidon
Spanish clortalidona (producto), clortalidona (sustancia), clortalidona, Clorftalidolona, Clortalidona, Ftalamudina
German Chlorphthalidolon, Chlortalidon, Chlorthalidon, Phthalamudin
Italian Clortalidone
Portuguese Clorftalidolona, Clortalidona, Ftalamudina