Sodium Bicarbonate

How it works

It provides bicarbonate that buffers hydrogen ions, raising blood and urinary pH; the more alkaline urine increases the solubility of uric acid and cystine, reducing crystallisation.

Prescribing in practice

• The sodium load can cause fluid retention and worsen hypertension or heart failure, and may cause hypokalaemia and metabolic alkalosis, so use cautiously where sodium must be restricted and monitor accordingly.
• It can alter the renal handling and effectiveness of some medicines through changes in urinary pH, so review concurrent drug therapy.
• Target the urinary pH appropriate to the indication when used for stone prevention to avoid over-alkalinisation, which can promote calcium phosphate stones.

Monitoring

Monitor urinary pH for stone or UTI indications, alongside electrolytes, bicarbonate, blood pressure and fluid status.

Counselling the patient

• Maintain a good fluid intake, particularly when used to help prevent stones.
• Report ankle swelling, breathlessness or muscle weakness, which may indicate fluid or salt imbalance.

Evidence & guidelines

Urinary alkalinisation with sodium bicarbonate is established for uric acid and cystine stone management and for symptomatic relief, and oral bicarbonate is supported by guidance for metabolic acidosis in CKD.