Thiazide Diuretic — Calcium Stone Prevention Pregnancy: Avoid in pregnancy — risk of neonatal thrombocytopenia and electrolyte disturbances

Hydrochlorothiazide

Brand names: HydroSaluric

Adult dose

Dose: 12.5-25 mg once daily

Route: Oral

Frequency: Once daily (morning)

Max: 50 mg/day for stone prevention

Used for hypercalciuric calcium oxalate nephrolithiasis — reduces urinary calcium excretion. Lower doses used for stone prevention than for hypertension

Paediatric dose

Dose: Seek specialist opinion N/A/kg

Route: Oral

Frequency: Seek specialist opinion

Max: Seek specialist opinion

Seek specialist opinion

Dose adjustments

Renal

Avoid if eGFR under 30 — ineffective and risk of electrolyte disturbances

Hepatic

Use with caution — hypokalaemia may precipitate encephalopathy

Paediatric weight-based calculator

Patient weight (kg)

Seek specialist opinion

Clinical pearls

EAU Stone Guidelines: Thiazide diuretics reduce urinary calcium excretion by 30-50% — indicated for recurrent calcium oxalate stones in patients with hypercalciuria
Must be combined with potassium supplementation or potassium-sparing diuretic — hypokalaemia reduces urinary citrate (citrate is a protective factor against calcium stones) — paradoxically worsening stone risk
Indapamide 1.5 mg SR is an alternative with equivalent calcium-lowering effect and better cardiovascular outcome data — preferred in many guidelines
Contraindicated if patient also has gout or hyperuricaemia — thiazides raise uric acid levels
Adequate fluid intake (above 2.5 L/day) is essential alongside all pharmacological stone prevention — most important intervention

Contraindications

Hyponatraemia
Hypercalcaemia
Refractory hypokalaemia
Addison disease

Side effects

Hypokalaemia
Hyponatraemia
Hyperuricaemia (worsens gout)
Impaired glucose tolerance
Postural hypotension
Erectile dysfunction

Interactions

Digoxin (hypokalaemia increases toxicity)
Lithium (thiazides increase lithium levels)
NSAIDs (reduce diuretic efficacy)
ACE inhibitors / ARBs (enhanced antihypertensive effect — synergistic)

Monitoring

Urinary calcium (24-hour collection — confirm hypercalciuria and response)
Electrolytes (K, Na, Mg)
Uric acid
Blood glucose
Blood pressure

Reference: BNFc; BNF 90; EAU Urolithiasis Guidelines 2024; AUA Stone Disease Guidelines 2019. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways