Bendroflumethiazide
Salures · Bendroflumetiazid Evolan
Inhibits the Na⁺/Cl⁻ cotransporter in the distal tubule and is the most commonly used thiazide diuretic for hypertension. The key point is that the dose–response curve for blood pressure flattens already at 2,5 mg, while the adverse effect curves for potassium, sodium, urate, and glucose continue to rise — higher doses therefore purchase side effects without blood pressure benefit. The antihypertensive effect is partly vasodilatory and persists after the initial volume reduction has normalised.
Hyponatraemia and hypokalaemia are the most common reason a thiazide-treated patient is admitted acutely, often an elderly woman also on an SSRI. Sodium can fall sharply within the first weeks after initiation and cause confusion, falls, and seizures — check electrolytes before issuing a year-long prescription.
Dosing in adults
| Indication | Regimen | Comment |
|---|---|---|
| Hypertension | 2,5 mg orally × 1 in the morning | standard dose; doses above 2,5 mg cause more side effects but little extra effect |
| Hypertension, insufficient effect | keep 2,5 mg and add ARB or calcium channel blocker | combine rather than increase the thiazide dose |
| Oedema in heart failure or other causes | 5–10 mg × 1 in the morning, then lowest maintenance dose | loop diuretic is first choice for significant oedema |
| Recurrent calcium-containing kidney stones | 2,5–5 mg × 1 | reduces urinary calcium excretion |
| Elderly or frail patient | 2,5 mg × 1, electrolytes after 1–2 weeks | highest risk of hyponatraemia and orthostasis |
Efficacy decreases with declining renal function and is in practice insufficient at eGFR below 30 ml/min — a loop diuretic is required instead. Contraindicated in severe renal impairment and anuria. At eGFR 30–60 the drug can be used but electrolytes and creatinine must be monitored more frequently.
Contraindicated in severe hepatic impairment. In cirrhosis the risk of hypokalaemia and thereby hepatic encephalopathy is increased; if a thiazide is used regardless, potassium must be monitored closely and supplemented.
Not used routinely in children. Evidence is insufficient and treatment should in applicable cases be managed by a paediatric nephrologist.
Do not increase the dose above 2,5 mg to obtain more blood pressure lowering — the additional effect does not materialise, but hypokalaemia, hyperuricaemia, and glucose elevation do. Also do not use thiazide at eGFR below 30: it does not work there and the patient needs a loop diuretic. In manifest gout, bendroflumethiazide is contraindicated, and in that patient losartan is a better antihypertensive alternative.
Pharmacokinetics
- BIOAVAIL.
- approximately 90 %
- t½
- 3–4 h
- PROTEIN BINDING
- approximately 95 %
- METABOLISM
- Partly hepatic
- EXCRETION
- Renal, approximately 30 % unchanged
- ONSET
- 1–2 h · maximum diuresis after approximately 4 h
- DURATION
- 12–18 h diuresis
- FULL BP EFFECT
- after 2–4 weeks