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Thiazide Diuretic Pregnancy: Diuretics are best avoided for the management of oedema of pregnancy or hypertension in pregnancy as their use may be associated with hypovolaemia, increased blood viscosity and reduced placental perfusion. There is inadequate evidence of safety in human pregnancy and some workers have described foetal bone marrow depression and blood disorders including neutropenia and thrombocytopenia. When given in late pregnancy, neonatal thrombocytopenia has been reported. Foetal and neonatal jaundice have also been described. As diuretics pass into breast milk, they should be avoided in mothers who wish to breast-feed. Bendroflumethiazide may suppress lactation.

Bendroflumethiazide

Brand names: Aprinox

Bendroflumethiazide is a thiazide diuretic used for hypertension and sometimes mild oedema; this page addresses its use in older patients, who are particularly susceptible to its metabolic and volume effects.

Adult dose

Dose: Essential hypertension: 2.5 mg in the morning, alone or in conjunction with other antihypertensive agents in more severe hypertension. Oedema: 5.0-10.0 mg once daily or on alternate days (maintenance 2.5-5.0 mg two or three times a week).
Route: Oral
Frequency: Hypertension: in the morning. Oedema: once daily or on alternate days; maintenance two or three times a week.
The SPC fetched is the generic Sandoz Bendroflumethiazide 2.5 mg tablets - same medicine, route and strength. The SPC prints NO elderly-specific dose: its only elderly statement is 'The dosage should be reduced in the elderly with impaired renal function', with no figure. The doses above are the adult doses. VERBATIM UK SPC §4.2 (product: Bendroflumethiazide 2.5 mg tablets; 'Route of administration: Oral'): 'ADULTS: Oedema: 5.0 - 10.0 mg once daily or on alternate days Maintenance: 2.5 - 5.0 mg two or three times a week Essential hypertension: 2.5 mg in the morning, alone or in conjunction with other antihypertensive agents in more severe hypertension. The dosage should be reduced in the elderly with impaired renal function.' §4.1: oedema 'associated with conditions such as congestive heart failure, nephrotic syndrome, cirrhosis of the liver'; essential hypertension 'as the sole antihypertensive agent or used concurrently with other specific hypotensive agents whose action it potentiates'. §2: 'Bendroflumethiazide 2.5 mg per tablet.' The SPC prints no maximum daily dose, so none is given here. Some sections of the product information we used were incomplete — check the full SPC. ELDERLY, VERBATIM §4.4: 'Some patients may be particularly susceptible to hyponatraemia, including the elderly and those with severe heart failure who are very oedematous' and 'Regular serum electrolyte determinations should be performed in the elderly and in patients receiving long-term therapy.' The page has no paediatric block (geriatrics page); the SPC's children's figures are on the general bendroflumethiazide page.

Dose adjustments

Renal

UK SPC §4.2: 'The dosage should be reduced in the elderly with impaired renal function' (no figure is given). Contraindicated in severe renal insufficiency (§4.3). §4.4: use with caution in renal impairment; renal function should be monitored during therapy.

Hepatic

Contraindicated in serious hepatic disorders (§4.3). §4.4: use with caution in hepatic impairment; thiazide diuretics may precipitate hepatic encephalopathy, particularly in case of electrolyte imbalance, and the diuretic must be stopped immediately if this occurs. No dose figure is given.

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via MHRA Products — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • Hypersensitivity to bendroflumethiazide or any of the excipients
  • Severe renal insufficiency
  • Addison's disease
  • Refractory hypokalaemia
  • Hyponatraemia
  • Hypercalcaemia
  • Serious hepatic disorders
  • Symptomatic hyperuricaemia

Side effects

  • Electrolyte imbalance: hypokalaemia, hypomagnesaemia, hyponatraemia (onset can be sudden and life-threatening), hypercalcaemia, hypochloraemic alkalosis; hyperuricaemia with or without gout
  • Postural hypotension; vasculitis
  • Hyperglycaemia; may precipitate diabetes mellitus and impair glycaemic control in diabetes
  • Increased triglyceride, total cholesterol, LDL and VLDL cholesterol concentrations
  • Blood dyscrasias including neutropenia, agranulocytosis, aplastic anaemia, thrombocytopenia and leucopenia
  • Pancreatitis; nausea, vomiting, diarrhoea, constipation, gastric irritation, dry mouth, thirst
  • Hypersensitivity reactions; rashes including exfoliative dermatitis; erythema multiforme; photosensitivity; pseudoporphyria; cutaneous lupus-like reactions and systemic lupus erythematosus
  • Choroidal effusion with visual field defect, transient myopia and acute angle-closure glaucoma (sulfonamide-type idiosyncratic reaction)
  • Headache, dizziness, paraesthesia, drowsiness
  • Impotence (reversible on discontinuing the drug)
  • Acute interstitial nephritis, oliguria, non-opaque urate calculi

Interactions

  • Lithium: bendroflumethiazide inhibits tubular elimination of lithium, raising plasma lithium and the risk of toxicity; avoid unless lithium levels and potassium can be closely monitored and the lithium dose adjusted
  • Pimozide, sertindole, thioridazine: diuretic-induced hypokalaemia increases the risk of ventricular arrhythmias; avoid concomitant use
  • Hypokalaemia increases the risk of cardiac arrhythmia with anti-arrhythmics, anti-histamines, anti-malarials, anti-psychotics and digoxin
  • Other antihypertensives (ACE inhibitors, angiotensin-II antagonists, calcium channel blockers, beta-blockers, alpha-blockers, hydralazine, diazoxide): enhanced hypotensive effect; the dose of the other drug may need reducing
  • Trimethoprim: severe hyponatraemia may occur
  • Carbamazepine: risk of hyponatraemia
  • Chlorpropamide: increased risk of hyponatraemia
  • Corticosteroids (and ACTH), other thiazides and other diuretics including acetazolamide and loop diuretics, amphotericin: increased risk of hypokalaemia
  • Calcium salts and vitamin D: risk of hypercalcaemia and milk-alkali syndrome
  • Alcohol, barbiturates, tricyclic antidepressants, MAOIs, aldesleukin, general anaesthetics, levodopa: enhanced hypotensive effect or postural hypotension
  • This interaction list may be incomplete — check the full SPC.

Monitoring

  • Serum electrolytes including potassium during treatment; regular serum electrolyte determinations in the elderly and in patients on long-term therapy
  • Magnesium as well as other electrolytes in patients with alcoholic cirrhosis
  • Renal function during bendroflumethiazide therapy
  • Regular ongoing monitoring and blood tests in elderly patients and in those on long-term treatment
  • Signs of fluid and electrolyte imbalance, especially in the presence of vomiting or during parenteral fluid therapy
  • Serum calcium: thiazides may cause intermittent slight elevation; discontinue thiazides before parathyroid function tests
  • Lithium levels and potassium concentrations if co-administered with lithium

Clinical monograph

How it works

It inhibits sodium-chloride reabsorption at the distal convoluted tubule, promoting natriuresis and diuresis, with a vasodilatory contribution to its long-term antihypertensive effect.

Prescribing in practice

  • Older patients are especially prone to hyponatraemia, hypokalaemia and volume depletion, which can cause confusion, falls and acute kidney injury, so use the lowest effective dose and monitor electrolytes.
  • It can precipitate or worsen gout, hyperglycaemia and hypercalcaemia, and raise lipids.
  • Combine cautiously with other drugs affecting sodium, potassium or renal perfusion, including other diuretics, ACE inhibitors and NSAIDs.

Monitoring

Monitor renal function and electrolytes (notably sodium and potassium) shortly after starting or changing dose and periodically thereafter.

Counselling the patient

  • Take it in the morning to avoid disturbed sleep from passing urine.
  • Report dizziness, marked weakness, confusion or muscle cramps.
  • During acute illness with vomiting or diarrhoea, seek advice as the medicine may need pausing.

Evidence & guidelines

Thiazide-type diuretics have established outcome benefit in hypertension trials and feature in NICE hypertension guidance, with cautious use advised in frail older people.

Reference: NICE NG136 (Hypertension); ALLHAT Trial; STOPP/START v3; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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