Pharmacology · Potassium-sparing diuretics
Triamterene !
A potassium-sparing diuretic that blocks the ENaC sodium channel, often paired with hydrochlorothiazide. It can cause kidney stones.
Updated 2026-11-01
Mechanism of action
Triamterene, a pteridine, blocks the epithelial sodium channel (ENaC) in the late distal tubule and collecting duct. Less sodium is reabsorbed and less potassium and hydrogen are secreted, independently of aldosterone. It is also a weak folic acid antagonist.
- Triamterene blocks ENaC in the collecting duct
- Less sodium reabsorbed
- K⁺ and H⁺ secretion falls
- Mild diuresis; potassium is spared
Pharmacokinetics
- Metabolism
- Mainly metabolised
- Elimination
- Part is recovered in the urine
- Onset and duration
- 2 to 4 hours after a dose
Indications
- Oedema from heart failure, cirrhosis or nephrotic syndrome Heart failure →
- Oedema from corticosteroids or secondary hyperaldosteronism
- With thiazides, to prevent low potassium
Adverse effects
Common
- Hyperkalaemia
- Nausea, vomiting, diarrhoea
- Dizziness and headache
- Photosensitivity
Contraindications
- Hyperkalaemia
- Anuria
- Severe or progressive kidney disease
- Severe liver disease
- Hypersensitivity to triamterene
Key interactions
- Potassium supplements, other potassium-sparing drugs, ACE inhibitors or ARBs
- Severe hyperkalaemia
- Indometacin
- Acute kidney failure has been reported
- Chlorpropamide
- Risk of severe hyponatraemia
- Quinidine
- Triamterene interferes with fluorescent quinidine assays
What is monitored
- Serum potassium
- Urea and creatinine
- Blood count in patients at risk of folate deficiency
- Blood glucose in diabetes
Nursing care
- Before giving: potassium and kidney function; stop potassium supplements when triamterene is added.
- Watch for weakness, slow pulse or palpitations (high potassium).
- Encourage fluids if not restricted, given the risk of kidney stones; report flank pain or blood in the urine.
- Teach: avoid potassium salt substitutes, protect skin from the sun.
Pregnancy and breastfeeding
Used only for oedema from pathological causes; it crosses the placenta.
Test yourself
Think of the answer, then tap the question to see it.
How does triamterene spare potassium?
It blocks the epithelial sodium channel (ENaC) in the collecting duct, so less sodium enters and less potassium is secreted.
Which kidney complication is typical of triamterene?
Kidney stones containing triamterene; caution is needed in patients with a history of stones.
Why can triamterene cause megaloblastic anaemia?
It is a weak folic acid antagonist, which matters in people with low folate, such as in cirrhosis.
Related drugs
Related conditions
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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - TRIAMTERENE capsule (DailyMed (U.S. National Library of Medicine), 2024); Triamterene: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2017); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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