Losartan: NHS information and prescribing guide

Losartan is a tablet. It is an angiotensin II receptor blocker (ARB). Losartan potassium is one of the most common ARBs prescribed on the NHS.

It is used for:

• High blood pressure (hypertension): NICE (NG136) suggests an ARB as a first choice for patients under 55. It is also an option instead of an ACE inhibitor at any age.
• Chronic heart failure: This is when ACE inhibitors are not suitable.
• Diabetic kidney disease: It helps slow kidney disease in patients with type 2 diabetes and proteinuria.
• Stroke prevention: This is for patients with high blood pressure and left ventricular hypertrophy.

Losartan works by blocking the angiotensin II type 1 (AT1) receptor. This stops angiotensin II from narrowing blood vessels. It also prevents the body from holding onto too much sodium and water.

This leads to lower blood pressure. It also reduces strain on the heart and protects the kidneys.

ACE inhibitors can cause a dry cough. Losartan does not affect bradykinin breakdown. This means it is much less likely to cause a cough. Medicines like ramipril or lisinopril often cause this cough.

Losartan is a tablet. You usually take it once a day. You can take it with or without food. You can take it at any time of day, but try to take it at the same time each day.

Dose by condition (BNF advice):

• High blood pressure: Start with 50 mg once daily. Increase to 100 mg once daily if needed. Patients over 75 or with liver problems may start at 25 mg daily.
• Heart failure: Start with 12.5 mg once daily. Increase the dose each week. Aim for a target dose of 150 mg once daily, if you can tolerate it.
• Diabetic kidney disease: Start with 50 mg once daily. Increase to 100 mg once daily based on your blood pressure response.
• Stroke prevention: Take 50 mg once daily. This is usually with a low-dose thiazide diuretic. Increase to 100 mg once daily if needed.

Important points about dosing:

• Check kidney function and potassium before starting. Monitor these regularly.
• If you have liver problems, start with a lower dose (25 mg).
• Do not combine losartan with an ACE inhibitor. This is called dual RAAS blockade. It raises the risk of high potassium and kidney injury.
• If you miss a dose, take it when you remember. Do not take it if it is almost time for your next dose. Do not take a double dose.

Losartan is usually well tolerated. Most common side effects are mild. They often go away as you continue treatment.

Common side effects:

• Dizziness, especially after the first dose or when the dose increases.
• High potassium (hyperkalaemia), found on blood tests.
• Tiredness.

Uncommon side effects:

• Headache, trouble sleeping.
• Feeling sick, diarrhoea, stomach pain.
• Muscle cramps or back pain.
• Skin rash.

Rare but serious side effects:

• Angioedema (swelling of the face, lips, or tongue).
• Sudden kidney injury.
• Very low blood pressure.
• Liver problems.

For more details on side effects, see our losartan side effects page.

Losartan has a key benefit over ACE inhibitors. It causes a dry cough very rarely. Clinical trials showed the cough rate with losartan was like a placebo.

This makes it a good choice for patients who get a cough from ACE inhibitors. About 10 to 15% of patients develop this cough.

Losartan can interact with some common medicines. Always tell your doctor or pharmacist about all your medicines.

Key interactions include:

• ACE inhibitors (ramipril, lisinopril): Do not take these with losartan. This is dual RAAS blockade. It increases the risk of high potassium and kidney problems.
• Potassium-sparing diuretics (spironolactone, amiloride): These increase the risk of high potassium. Close monitoring is needed if you must take both.
• NSAIDs (ibuprofen, naproxen, diclofenac): These can make losartan less effective at lowering blood pressure. They also increase the risk of kidney damage. Use the lowest dose for the shortest time.
• Lithium: Losartan can raise lithium levels. This could lead to toxicity. Monitor lithium levels more often.
• Potassium supplements and salt substitutes: These increase the risk of high potassium.
• Trimethoprim: This can raise potassium levels when taken with losartan.

The BNF has a full list of interactions. Your pharmacist will check for interactions each time you get a new medicine.

Regular checks are vital for safe losartan treatment. NICE and the BNF suggest the following schedule.

Before starting losartan:

• Measure blood pressure.
• Check kidney function (eGFR) and electrolytes, including potassium.
• Assess your risk factors for heart and blood vessel disease.

After starting or changing the dose:

• Check blood pressure within 2 to 4 weeks.
• Check kidney function and potassium at 1 to 2 weeks.
• Do further checks at 4 to 6 weeks if your condition is stable.

Long-term monitoring:

• Check blood pressure at least once a year. Check more often if it is not at target.
• Check kidney function and potassium at least once a year.
• Monitor more often if you have chronic kidney disease, heart failure, diabetes, or take other medicines that affect potassium.

Signs to report:

• A large rise in creatinine (over 30% above your usual level) may mean you need a lower dose or to stop the medicine.
• Potassium above 5.5 mmol/L needs action.
• Blood pressure staying below 90/60 mmHg with symptoms may mean the dose is too high.

Your GP practice will usually arrange these tests. They are part of routine management for long-term conditions. If you have not had recent blood tests, ask at your next appointment.

Losartan is a generic medicine. It is widely available on the NHS. It is one of the most cost-effective ARBs.

Key prescribing details:

• It comes in 12.5 mg, 25 mg, 50 mg, and 100 mg tablets.
• It is also available as a tablet combined with hydrochlorothiazide (a diuretic).
• Generic losartan potassium costs the NHS about 2 to 4 pence per tablet.
• It is on local formularies across England, Scotland, Wales, and Northern Ireland.
• You can get it on a standard NHS prescription.

NICE guidance:

NICE (NG136) recommends an ARB as an alternative to an ACE inhibitor. This is for when a cough or other side effects occur.

Losartan and candesartan are the most common ARBs prescribed in UK primary care.

Repeat prescriptions:

Most patients get losartan as a repeat prescription. The NHS Electronic Prescription Service (EPS) sends your prescription directly to your chosen pharmacy. This makes collection easy.

If you have questions about your losartan prescription, your community pharmacist can always help.