Losartan

How it works

It selectively blocks the angiotensin-II type-1 (AT1) receptor, causing vasodilatation, reduced aldosterone secretion and lower blood pressure without affecting bradykinin metabolism.

Prescribing in practice

• Contraindicated in pregnancy because it can cause foetal harm, and it should be stopped if pregnancy is planned or confirmed.
• It can cause hyperkalaemia and acute kidney injury, particularly with renal artery stenosis, volume depletion, or concurrent potassium-raising drugs or NSAIDs.
• Do not combine with an ACE inhibitor or aliskiren because dual renin-angiotensin blockade increases the risk of hyperkalaemia, hypotension and renal impairment.

Monitoring

Monitor blood pressure, renal function and serum potassium, especially after initiation or dose changes.

Counselling the patient

• Tell your doctor at once if you become or plan to become pregnant.
• Dizziness can occur initially, particularly on standing; rise slowly.

Evidence & guidelines

Supported by major outcome trials in hypertension and diabetic nephropathy and recommended in NICE hypertension guidance.