Urinary Alkalinising Agent
Pregnancy: Use with caution; avoid large doses in pregnancy
Sodium Bicarbonate
Brand names: Sodium Bicarbonate (generic)
Adult dose
Dose: 3-6 g daily in divided doses (oral); 1-2 mmol/kg IV (metabolic acidosis)
Route: Oral / Intravenous
Frequency: Two to three times daily (oral); as required (IV)
Max: Titrate to urine pH target of 6.5-7.0 (uric acid stones); 7.0-7.5 (cystine stones)
For urinary alkalinisation in uric acid and cystine nephrolithiasis. Potassium citrate is preferred (less sodium load) but bicarbonate is an alternative. Monitor urine pH with dipstick
Paediatric dose
Dose: 1-2 mmol/kg/day (oral alkalinisation) mmol/day/kg
Route: Oral
Frequency: Divided doses
Max: As determined by urine pH monitoring
Dose titrated to achieve target urine pH. Seek specialist opinion for dosing in renal tubular acidosis and cystine stones in children
Dose adjustments
Renal
Use with caution in renal impairment — risk of sodium and water retention; monitor electrolytes
Hepatic
No specific adjustment; use with caution in hepatic disease with ascites (sodium load)
Paediatric weight-based calculator
Dose titrated to achieve target urine pH. Seek specialist opinion for dosing in renal tubular acidosis and cystine stones in children
Clinical pearls
- EAU Urolithiasis Guidelines: urinary alkalinisation is the cornerstone of uric acid stone prevention and dissolution — uric acid stones can fully dissolve with adequate alkalinisation (target pH 6.5-7.0)
- Potassium citrate is preferred over sodium bicarbonate in most patients — provides potassium supplementation (citrate chelates urinary calcium reducing calcium stone risk) and avoids sodium load
- Sodium bicarbonate preferred when potassium citrate is contraindicated (hyperkalaemia, renal failure) or not tolerated
- Uric acid stones are unique in being potentially fully dissolvable without intervention — medical expulsive therapy with alkalinisation can avoid ureteroscopy
- Cystine stones: target higher pH (7.0-7.5) — cystine solubility markedly increases above pH 7.0; sodium bicarbonate or potassium citrate both appropriate
Contraindications
- Metabolic alkalosis
- Hypochloraemia
- Severe oedema or heart failure (sodium load)
Side effects
- Belching and flatulence (CO2 release)
- Metabolic alkalosis (overdose)
- Sodium and fluid retention (hypertension, oedema)
- Hypokalaemia (secondary to alkalosis)
Interactions
- Lithium (alkaline urine increases renal clearance — reduces lithium levels)
- Ketoconazole (reduced absorption in alkaline environment)
- Tetracyclines (reduced absorption)
- Aspirin (increases renal aspirin excretion)
Monitoring
- Urine pH (twice daily with dipstick — before breakfast and at bedtime)
- Electrolytes (Na, K)
- Blood pressure (sodium load)
- Serum bicarbonate
Reference: BNFc; BNF 90; EAU Urolithiasis Guidelines 2024; AUA Stone Disease Guidelines 2019. Verify against your local formulary and the latest BNF before prescribing.
Related
Curated clinical cross-links plus same-class fallbacks.
Calculators