Chlorthalidone: Treatment for hypertension


A prescription medication called chlorthalidone is used to treat high blood pressure (hypertension). Bringing down high blood pressure reduces the risk of heart attacks, kidney issues, and strokes. Additionally, it is used to lessen the amount of salt and water that the body retains due to ailments like heart failure, liver illness, and kidney disease. Edema and breathing issues brought on by fluid in the lungs can both be reduced by reducing excess salt and water in the body. A “water pill” is chlorthalidone (diuretic). Particularly when you first take the medicine, it causes you to produce more urine. In order to facilitate easier blood flow, it also aids in relaxing the blood vessels.

Chlorthalidone is also used to treat fluid retention (edema) brought on by severe liver disease (cirrhosis), kidney illness, congestive heart failure, or medication for hormone or steroid use.

Mechanism of action

To begin with, Chlorthalidone works as a medication by blocking the sodium-chloride symporter in the nephron’s distal convoluted tubule. Although its chemical structure has been somewhat altered, its mechanism of action is comparable to that of a thiazide diuretic. The sulfonamide group, which is present in both thiazide and thiazide-like diuretics, serves to inhibit carbonic anhydrase and its antagonistic activity at the distal convoluted tubule.

Chlorthalidone prevents chloride from being absorbed by inhibiting the Na/Cl symporter at the level of the distal convoluted tubule. The distal convoluted tubule of the nephron maintains more sodium by blocking sodium reabsorption here. The osmotic gradient changes as a result of the lack of reabsorption, and fluid distribution shifts from the tubule’s exterior to its inside. Its increased sodium content causes a higher intratubular volume, enhancing its diuretic impact. Intravascular water and solute concentration are decreased due to the increased excretion of sodium and extracellular fluid. The patient has reduced hydrostatic pressure, which has led to a clinical reduction in blood pressure by lowering the intravascular volume and osmotic gradient.

Also, check out Pantoprazole- Uses, Dosage & Side Effects – My Biology Dictionary


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Only oral medications containing chlorthalidone are readily available.

Potency: 25 mg and 50 mg

Heart failure: commencing at 12.5 mg or 25 mg per day, with a 100 mg daily maximum.

The maximum dose for generalized edema is 200 mg per day, commencing at 50 g or 100 mg per day.

25 mg/day for calcium nephrolithiasis

When choosing the dose, the patient’s age must also be taken into account. Chlorthalidone should be used at lower doses in the elderly (those over 65), commencing at 6.25 mg to 12.5 mg per day and titrating gently as previously described.

Side effects

Following are a few side effects of Chlorthalidone:

  • Cardiovascular: low blood pressure (hypotension), vasculitis, lightheadedness when standing
  • Dermatologic: sun sensitivity, sunburn-induced skin irritation, rash, hives, and blood vessel inflammation
  • Endocrine/metabolic: electrolyte abnormalities, hyperglycemia, hyperuricemia, and glycosuria;
  • Gastrointestinal: gastrointestinal discomfort, diarrhoea, constipation, appetite loss, nausea, vomiting, cramps, and yellowing of the skin and eyes; (jaundice)
  • Musculoskeletal: weakness, spasticity, or involuntary muscle movement
  • Neurologic symptoms include vertigo, headaches, numbness/tingling, and vertigo. Ophthalmologic symptoms include poor color vision and impaired vision.
  • Psychiatric symptoms include restlessness.
  • Reproductive: incapacity

Rare side effects

  • Cardiovascular System: irregular heartbeat (cardiac dysrhythmia)
  • Dermatologic: toxic epidermal necrolysis, Stevens-Johnson syndrome, scaling eczema
  • Hematologic: abnormality of the hematopoietic structure, including low white blood cell count, lack of granulocytes in the blood (agranulocytosis), low blood platelet count, and no red blood cell formation (aplastic anaemia)
  • Hepatic: harm to the liver
  • Systemic lupus erythematosus (immunologic) (SLE)
  • Lung fluid: respiratory (pulmonary edema)

Chlorthalidone and other drugs may interact.

If you use any other drugs, vitamins, or herbal supplements, chlorthalidone oral tablet may interact with them. When a substance modifies how a drug functions, there is an interaction. This could be hazardous or stop the medication from working properly.

However, your doctor needs to closely monitor all of your prescriptions to help you prevent interactions. Tell your doctor about all of the drugs, supplements, and herbal remedies you are using. Speak to your doctor or pharmacist to learn how this medication may interact with other medications you are taking.


  • Use with caution in cases of systemic lupus erythematosus, low blood pressure (hypotension), fluid or electrolyte imbalance, excess cholesterol (hypercholesterolemia), and excess uric acid in the blood (hyperuricemia), gout, senior age, a history of allergies, or bronchial asthma.
  • Steer clear of using lithium concurrently (reduction of lithium dosage by 50 per cent may be necessary).
  • Might make digitalis more hazardous.
  • Patients with sulfa medication allergies may exhibit cross-sensitivity.
  • Possibility of male sexual dysfunction.
  • Photosensitization could happen.
  • Electrolyte problems, such as hypokalemia (low blood potassium level), hyponatremia (low blood sodium level), and hypochloremic alkalosis (low blood chloride ion level), may happen.

To conclude, Chlorthalidone is a very effective drug and is used very commonly. However, one should always consult his/her doctor for the same.

Thank you for reading!

Team MBD

Read more- Chlorthalidone – StatPearls – NCBI Bookshelf (


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