Hydrochlorothiazide

Thiazide Diuretic·Cardiovascular - Diuretics

Hypertension, mild heart failure

PBSDIURETICDithiazide, Atacand Plus (combo), Micardis Plus (combo)12.5 mg tabletS4+1

Max Dose

50 mg/day

Half-life

6–15 h

Hypokalemia

RISK

Hyponatremia

RISK

Rapid Summary

Overview

Thiazide diuretic. Lowers blood pressure via mild diuresis and long-term direct vasodilation. Highly prone to causing metabolic disturbances.

Maximum Dose

Max 50 mg/day (higher doses cause toxicity with no extra BP benefit).

Clinical Focus

Elderly patients are exceptionally prone to severe, life-threatening hyponatremia on this drug.

Bottom Line

Hydrochlorothiazide is a cheap, effective first-line thiazide diuretic for hypertension, but causes hyponatraemia and hypokalaemia requiring regular electrolyte monitoring.

Formulation & Access

Brand Names

Dithiazide, Atacand Plus (combo), Micardis Plus (combo)

Oral Routes

Tablets (12.5 mg, 25 mg). Frequently combined with ACEi/ARBs.

Prescribing & PBS

Unrestricted General Benefit (S4).

Indications & Use

Primary

PBSTGA

Hypertension, mild heart failure.

Clinical Place

Excellent combination agent with ACEi/ARBs, which counteract the thiazide-induced hypokalemia.

Quick reference

Class & Role

Thiazide Diuretic — Thiazide diuretic.

Route / Formulation

Tablets (12.5 mg, 25 mg). Frequently combined with ACEi/ARBs. (Dithiazide, Atacand Plus (combo), Micardis Plus (combo))

Usual Dose & Max

PO 12.5–25 mg OD (morning). Max 50 mg/day.

Key Indication Doses

Hypertension: PO 12.5–25 mg OD (morning). Max 50 mg/day. Heart Failure (Mild): PO 25–50 mg OD. Elderly / Frail: Strictly start at 12.5 mg OD.

Best Uses

Hydrochlorothiazide is a cheap, effective first-line thiazide diuretic for hypertension, but causes hyponatraemia and hypokalaemia requiring regular electrolyte monitoring.

Avoid / Cautions

Anuria, severe sulfa allergy, refractory hypokalemia. Pregnancy Category C.

Key Risks

Electrolytes: Hyponatremia (can cause seizures/coma), Hypokalemia, Hypomagnesemia, HYPERcalcemia. Metabolic: Hyperuricemia (triggers gout attacks), hyperglycemia, hyperlipidemia. Dermatological: Photosensitivity, increased risk of non-melanoma skin cancers (SCC/BCC) with long-term use.

Key Interactions

Lithium (thiazides reduce lithium clearance by 25-40%, causing severe toxicity). NSAIDs + ACEi + Thiazide.

Monitoring

Baseline and routine U&E. Monitor BSL in borderline diabetics. Check uric acid if joint pain occurs. Monitor BP.

Clinical Pearl

Unlike loop diuretics (which waste calcium), thiazides *retain* calcium. This makes them excellent for hypertensive patients who also have osteoporosis or recurrent calcium kidney stones.

Access

Dithiazide, Atacand Plus (combo), Micardis Plus (combo)12.5 mg tablet

Brand: Dithiazide, Atacand Plus (combo), Micardis Plus (combo)
Formulation: Tablets (12

Hydrochlorothiazide

Thiazide Diuretic·Cardiovascular - Diuretics

Hypertension, mild heart failure

PBSDIURETICDithiazide, Atacand Plus (combo), Micardis Plus (combo)12.5 mg tabletS4+1

Max Dose

50 mg/day

Half-life

6–15 h

Hypokalemia

RISK

Hyponatremia

RISK

Rapid Summary

Overview

Thiazide diuretic. Lowers blood pressure via mild diuresis and long-term direct vasodilation. Highly prone to causing metabolic disturbances.

Maximum Dose

Max 50 mg/day (higher doses cause toxicity with no extra BP benefit).

Clinical Focus

Elderly patients are exceptionally prone to severe, life-threatening hyponatremia on this drug.

Bottom Line

Hydrochlorothiazide is a cheap, effective first-line thiazide diuretic for hypertension, but causes hyponatraemia and hypokalaemia requiring regular electrolyte monitoring.

Formulation & Access

Brand Names

Dithiazide, Atacand Plus (combo), Micardis Plus (combo)

Oral Routes

Tablets (12.5 mg, 25 mg). Frequently combined with ACEi/ARBs.

Prescribing & PBS

Unrestricted General Benefit (S4).

Indications & Use

Primary

PBSTGA

Hypertension, mild heart failure.

Clinical Place

Excellent combination agent with ACEi/ARBs, which counteract the thiazide-induced hypokalemia.

Quick reference

Class & Role

Thiazide Diuretic — Thiazide diuretic.

Route / Formulation

Tablets (12.5 mg, 25 mg). Frequently combined with ACEi/ARBs. (Dithiazide, Atacand Plus (combo), Micardis Plus (combo))

Usual Dose & Max

PO 12.5–25 mg OD (morning). Max 50 mg/day.

Key Indication Doses

Hypertension: PO 12.5–25 mg OD (morning). Max 50 mg/day. Heart Failure (Mild): PO 25–50 mg OD. Elderly / Frail: Strictly start at 12.5 mg OD.

Best Uses

Hydrochlorothiazide is a cheap, effective first-line thiazide diuretic for hypertension, but causes hyponatraemia and hypokalaemia requiring regular electrolyte monitoring.

Avoid / Cautions

Anuria, severe sulfa allergy, refractory hypokalemia. Pregnancy Category C.

Key Risks

Key Interactions

Lithium (thiazides reduce lithium clearance by 25-40%, causing severe toxicity). NSAIDs + ACEi + Thiazide.

Monitoring

Baseline and routine U&E. Monitor BSL in borderline diabetics. Check uric acid if joint pain occurs. Monitor BP.

Clinical Pearl

Unlike loop diuretics (which waste calcium), thiazides *retain* calcium. This makes them excellent for hypertensive patients who also have osteoporosis or recurrent calcium kidney stones.

Access

Dithiazide, Atacand Plus (combo), Micardis Plus (combo)12.5 mg tablet

Brand: Dithiazide, Atacand Plus (combo), Micardis Plus (combo)
Formulation: Tablets (12