Bendroflumethiazide (Bendrofluazide) — NZ Medication Guide | KiwiMeds

What is bendroflumethiazide?

Bendroflumethiazide (also known as bendrofluazide) is a thiazide diuretic — a type of water tablet used to treat high blood pressure and fluid retention. It is one of several thiazide diuretics available in New Zealand and is fully funded by Pharmac. The funded NZ brand is Arrow-Bendrofluazide, available as 2.5mg and 5mg tablets.

What is it used for?

According to the New Zealand Formulary (NZF), bendroflumethiazide is indicated for oedema (fluid retention) and hypertension (high blood pressure). For hypertension, the NZF recommends 2.5mg once daily in the morning — higher doses increase adverse effects without much additional blood pressure benefit.

How does it work?

Thiazide diuretics inhibit the reabsorption of sodium and chloride at the beginning of the distal convoluted tubule of the kidney, promoting excretion of water and increasing urine volume. At lower doses used for hypertension, the blood pressure lowering effect is mainly due to reduced vascular resistance rather than fluid removal.

How to take it

Taken once daily in the morning as directed by your doctor. For hypertension: typically 2.5mg once daily. The NZF notes that the maximum antihypertensive dose is 2.5mg — higher doses do not add significant blood pressure benefit and increase adverse effects. For oedema: 5–10mg once daily or on alternate days.

Common side effects

According to the NZF, common side effects include mild gastrointestinal disturbances (nausea, vomiting, constipation, diarrhoea), electrolyte disturbances (particularly low potassium/hypokalaemia, low sodium/hyponatraemia, low magnesium/hypomagnesaemia, and elevated calcium), raised blood glucose (hyperglycaemia), raised uric acid (hyperuricaemia — can trigger gout), and postural hypotension (dizziness when standing). Erectile dysfunction has also been reported.

Serious side effects to watch for

Seek medical attention for: serious blood disorders (agranulocytosis, thrombocytopenia — rare), severe allergic skin reactions including Stevens-Johnson Syndrome or Toxic Epidermal Necrolysis (very rare), pancreatitis (severe abdominal pain), and acute angle-closure glaucoma (sudden eye pain and blurred vision — seek urgent eye care).

Important drug interactions

Key interactions per the NZF include: potassium-lowering medicines (ACE inhibitors, corticosteroids — risk of severe hypokalaemia), lithium (thiazides reduce lithium excretion — may cause toxicity), NSAIDs (reduce diuretic and antihypertensive effect), antidiabetic medicines (thiazides may raise blood sugar), and other antihypertensives (additive blood pressure lowering).

Things to avoid

Avoid NSAIDs (ibuprofen, naproxen) — they reduce the effectiveness of bendroflumethiazide and can worsen kidney function. Avoid excessive alcohol — increases blood pressure lowering effects and dehydration risk. People with gout should be aware that bendroflumethiazide can raise uric acid levels.

NZ-specific information

Bendroflumethiazide is fully funded by Pharmac. The NZ-funded brand is Arrow-Bendrofluazide (Teva) in 2.5mg and 5mg tablets. Regular monitoring of renal function and electrolytes (sodium, potassium, magnesium) is recommended, particularly in the elderly, at high doses, and if other medicines are taken that may cause electrolyte disturbances. The NZF provides a Patient Information Leaflet (PIL) for bendroflumethiazide in English and Te Reo Māori.

Frequently asked questions

Why is my blood pressure tablet a “water tablet”? Thiazide diuretics were the original blood pressure medicines and remain effective and affordable. At low doses they work primarily by relaxing blood vessels. Do I need potassium supplements? At the low dose used for hypertension (2.5mg), potassium loss is usually small. Your GP will check your electrolytes. Can I take ibuprofen for pain? Avoid ibuprofen — it reduces bendroflumethiazide’s effectiveness. Use paracetamol instead.

Related medications

Related: Furosemide, Amlodipine, Lisinopril. Condition: Hypertension.

References & Further Information

The following New Zealand and international resources were used to inform this page:

• New Zealand Formulary (NZF) — Bendroflumethiazide (Bendrofluazide)
• Pharmac — New Zealand Pharmaceutical Schedule
• Medsafe — New Zealand Medicines and Medical Devices Safety Authority
• BPAC NZ — Best Practice Advocacy Centre New Zealand