Losartan at a glance
Medicine class
Angiotensin II receptor blocker (ARB).
How it is taken
Swallow the tablet with water, with or without food.
Routine checks
Blood pressure, kidney function and blood electrolytes—especially potassium—usually require monitoring.
What is Losartan used for?
Licensed uses include:
Essential hypertension in adults and children and adolescents aged 6–18 years.
Kidney disease in adults with hypertension, type 2 diabetes and clinically significant proteinuria, as part of antihypertensive treatment.
Chronic heart failure in clinically stable adults with reduced left-ventricular ejection fraction when an ACE inhibitor is unsuitable because of intolerance—particularly cough—or contraindication. People stable on an ACE inhibitor should not be switched solely for this indication.
Reducing stroke risk in adults with hypertension and left-ventricular hypertrophy documented by ECG.
How does Losartan work?
Losartan and its active metabolite block angiotensin II at AT1 receptors. This reduces blood-vessel narrowing and aldosterone effects, lowering blood pressure and reducing strain on the heart and kidneys. Losartan does not inhibit bradykinin breakdown.
Losartan preparations and strengths
Tablet
Route: Oral
Strengths: 12.5 mg, 25 mg, 50 mg, 100 mg
How to take Losartan
Follow the dispensing label and product leaflet. Do not stop losartan without discussing it with the prescriber.
Swallow the tablet with a glass of water.
It can be taken with or without food.
Avoid grapefruit juice because it may reduce formation of losartan’s active metabolite.
If swallowing tablets is difficult, ask a pharmacist before altering them. Crushing film-coated tablets is off-label and they may taste bitter.
Losartan side effects
Common or expected effects
- Dizziness or vertigo
- Tiredness or weakness
- Headache
- Nausea, vomiting or abdominal discomfort
- Swelling of the legs, ankles or feet
- Raised blood potassium, usually identified by a blood test
Get urgent medical advice
- Swelling of the face, lips, tongue or throat, or breathing difficulty: possible angioedema or anaphylaxis.
- Fast or irregular heartbeat.
- Yellow skin or eyes with nausea or vomiting: possible liver injury.
- Severe persistent abdominal pain with nausea, vomiting or diarrhoea: possible intestinal angioedema.
- Marked weakness, abnormal heartbeat or reduced urine output: possible electrolyte or kidney problems.
Losartan in pregnancy
Losartan is not normally used during pregnancy and is contraindicated during the second and third trimesters because it can seriously affect fetal kidneys, amniotic fluid and development. Discuss an alternative before planning pregnancy. If pregnancy occurs, contact the prescriber promptly.
Losartan while breastfeeding
Evidence during breastfeeding is very limited, so a medicine with better-established safety information is usually preferred, particularly for a newborn or premature infant. Losartan may occasionally be considered after specialist assessment; observe the infant for unusual sleepiness, pallor, poor feeding, inadequate weight gain and, in younger infants, reduced wet nappies.
Losartan interactions
Tell the prescriber or pharmacist about all medicines, supplements and salt substitutes. Important examples include:
Potassium supplements, potassium-containing salt substitutes, potassium-sparing diuretics, trimethoprim or heparin
These can increase blood potassium; combined use may require avoidance or closer blood-test monitoring.
NSAIDs, including ibuprofen and anti-inflammatory doses of aspirin
They may reduce the blood-pressure effect and increase the risk of kidney impairment and high potassium, particularly with dehydration or existing kidney disease.
Common questions about Losartan
Answers are fully visible for fast scanning and source review.
Can losartan potassium be taken with food?
Yes. The tablets may be taken with or without food and swallowed with water.
Can I drink grapefruit juice while taking losartan potassium?
It is best avoided because it may reduce formation of losartan’s active metabolite and potentially reduce its effect.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.