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Thiazide diuretics are used to treat high blood pressure and heart failure. This article profiles the medication, its benefits and side effects.


Bendrofluazide: Neo-Naclex

Cyclopenthiazide: Prothiazide, Navidrex

Indapamide: Napamide, Naplin, Natrilix\t\t\t

USE: high blood pressure/ heart failure

Thiazide diuretics and related compounds are used in mild or moderate heart failure and hypertension (high blood pressure). They have a potent action, and work by inhibiting sodium reabsorption in the kidneys having an anti-hypertensive effect and reducing oedema (excess body water).

Diuretics have a diuresis effect (increased urine output) which can act within 1-2 hours (last for over 12 hours), therefore these medicines are best taken in the morning to prevent interference with sleep.

They have been extensively studied and shown to reduce the risk of both stroke and heart attack in people with high blood pressure.

They are usually started in low dosages which are often very effective.


  • Severe kidney and liver impairment
  • Hypokalaemia (low potassium levels) and hypercalcaemia (high calcium levels)
  • Elderly
  • Vomiting or diarrhoea
  • Diabetes and gout (aggravates)
  • Pregnancy and breastfeeding

Side effects:

They are generally very well tolerated, especially in low doses.

Thirst, dizziness, constipation, mild stomach problems, and impotence have been reported. Thiazides can lower potassium levels causing malaise, muscle weakness, anorexia, dizziness, nausea and vomiting.

They also impair glucose tolerance, increase uric acid and lipid levels which affects diabetics, gout and hyperlipidaemic patients respectively. These side effects are usually minimal with the low dosages often used.

Rarely: skin rash, blood disorders.


Increased risk of toxicity seen with lithium, NSAIDs (Aspirin, Cataflam, Nurofen).

Thiazides affect diabetes control in patients on sulphonylureas and enhance hypotensive effect with alcohol, antihypertensives, barbituates, narcotics etc.

Increased risk of hypokalaemia with other diuretics, ulcer-healing drugs and some antifungals.

Patient information:

  • Follow the instructions on the label of this medicine and don't stop taking this medicine unless directed
  • Blood tests to monitor potassium are needed
  • This medicine is best taken IN THE MORNING with a glass of water
  • Missed dose: take the next dose as soon as you remember (do not double dose)
  • Avoid taking other medicines unless directed by your doctor/pharmacist
  • Contact your doctor or seek medical attention if side effects are severe or ongoing

See also:

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