Losartan: uses, side effects and cautions

The NHS says losartan treats high blood pressure and heart failure and is prescribed for kidney disease caused by type 2 diabetes. It is an angiotensin receptor blocker, a class that is related to, but different from, ACE inhibitors, and it is only available with a prescription. Cozaar is a commonly seen brand.

Because ARBs rarely cause the dry cough associated with ACE inhibitors, doctors sometimes choose one for people who could not tolerate an ACE inhibitor.

Most adults aged 18 or over can take losartan, and it may be suitable for children aged 6 to 17. It is unsuitable if you have had an allergic reaction to another ARB, if you have severe heart failure, liver problems or a history of angioedema, and in pregnancy or breastfeeding, where alternatives are usually offered.

Losartan comes as tablets. Most people take one once a day. You can take it at any time but should keep to the same time each day, with water, with or without food.

The NHS page gives no fixed dose figures; how much you need depends on why you are taking it, and doses may change after several weeks. Usually it is long-term treatment. If you miss a dose, take the next as normal and never double up. Taking too much can be dangerous: call NHS 111 and take the packet to A&E if directed. Do not stop unless your doctor says so.

Your doctor will arrange blood tests and blood pressure checks to see how it is affecting your blood pressure and kidneys.

Common effects are dizziness, tiredness, headache, tummy pain, nausea, vomiting and swelling of legs, ankles or feet. If these bother you or do not go away, tell a pharmacist or doctor; do not stop the tablets on your own.

Serious but rare effects include anaphylaxis, with swollen throat or tongue, itchy raised rash and difficulty breathing, and a fast or irregular heartbeat. Call NHS 111 if you think a serious effect is occurring. If told to go to A&E, do not drive yourself.

Named interactions: other blood pressure medicines including beta blockers and ACE inhibitors such as lisinopril, diuretics such as spironolactone, NSAIDs including ibuprofen, fluconazole, tricyclic antidepressants such as amitriptyline, antipsychotics such as quetiapine and lithium. Potassium supplements and potassium-containing salt substitutes are also on the list because potassium can build up.

Grapefruit juice may stop the medicine working properly. Limit alcohol, since it can raise the risk of side effects. Losartan should not impair driving, but wait until dizziness or tiredness has gone before you drive.

Losartan is not usually used during pregnancy and the doctor may offer a different treatment. It is also not usually used while breastfeeding. The NHS points to the Bumps website for pregnancy information on ARBs, and gives no fertility guidance on its page.

Other ARBs include candesartan, valsartan and irbesartan; ACE inhibitors such as ramipril are another group. Report suspected side effects to the Yellow Card scheme.