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Medications

Thiazide Diuretics

Last Updated on October 16, 2022

Classifications:

(i) Thiazide e.g. hydrochlorothiazide
(ii) Thiazide-like diuretics e.g. chlorthalidone (CTD), indapamide

Mechanisms of Action

  • Blocks Na+-Cl− co-transporter at the beginning of distal convoluted tubule → inhibits odium re absorption
  • Natriuretics would alter long term sodium balance → reduced peripheral vascular resistance & sustained BP reduction
  • As more sodium reaching collecting duct, hypokalaemia occurs

Indications

  • Hypertension

Adverse effects

  • Electrolyte imbalance
    • Hyponatremia
    • Hypokalaemia
    • Hypercalcaemia
  • Urinary frequency
  • Dehydration
  • Postural hypotension
  • Gout
  • Erectile dysfunction
  • Impaired glucose tolerance

Rare adverse effects

  • Thrombocytopenia
  • Photosensitivity rashes
  • Pancreatitis

Dosage

Hypertension

  • Single / combine with other anti-HTN

Diuretics

Starting dose

Recommended maximum daily dose

Remark

Hydrochlorothiazide

12.5 mg OD

25 mg OD

>25 mg OD more likely to cause electrolyte (esp hyponatraemia) & metabolic adverse effect

Amiloride/hydrochlorothiazide 5 mg/50 mg

1 Tab OD

1 Tab OD

Indapamide SR

1.5 mg OD

1.5 mg OD

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