Losartan - Use | Dose | Side Effects

This article was medically reviewed by M.Pharm, Marko Tanaskovic on August 12, 2018. To read more about an author, click here.

Losartan is a drug from the group of angiotensin II receptor antagonists also known as angiotensin II receptor blockers (ARB). By blocking the receptors that are intended for binding of angiotensin II, Losartan reduces the effect of this substance whose main feature is a strong vasoconstrictor effect. In this way, Losartan improves blood flow and lowers the pressure on the blood vessels.

The main advantage of the angiotensin II receptor blockers compared to ACE inhibitors is that these drugs do not cause cough as a side effect.

Losartan has a much greater effect on blood pressure, than on the heart rate. Losartan reduces the risk of stroke by 25%.


The only contraindications for use of Losartan are pregnancy and severe liver damage. In these situations, Losartan should not be used.

Losartan should be administered with extra precautions in patients who have low blood pressure, because in such patients, Losartan can further lower the blood pressure. Symptomatic hypotension may occur at the start of therapy especially in patients who have an imbalance of electrolytes and water.

Losartan is a drug which reduces the excretion of potassium, which directly increases the level of this electrolyte in the blood. Patients who already have high potassium levels or taking potassium-sparing diuretics (e.g. spironolactone, triamterene and amiloride) should not use Losartan. High potassium levels in the blood will lead to dangerous cardiac arrhythmias. Studies have shown that the risk of hyperkalemia is increased in diabetic patients and in patients who have renal insufficiency (renal failure).

Studies have shown that the concentration of Losartan in the blood is significantly higher in patients who have serious liver toxicity, and for this reason the use of this drug in patients who have liver disorders should be avoided.

Losartan may cause kidney damage, bearing in mind that its mechanism of action is based on the inhibition of the renin-angiotensin-aldosterone system, which is located mainly in the kidney. Losartan should never be used in patients who have a renal artery stenosis.

Losartan should not be used for lowering blood pressure in patients who have hyperaldosteronism, because the ARB medicines are ineffective in these situations.

Losartan should not be used in patients having ischemic heart disease or ischemic cerebrovascular disease, because an excessive fall in blood pressure in these patients may lead to myocardial infarction, stroke and kidney damage.

Losartan, pregnancy and breastfeeding

Clinical studies have shown that the use of Losartan between 20th to 31st week of pregnancy can cause fetus malformations as following:

    Poorly developed lung tissue (also called fetal pulmonary hypoplasia)

    Hypoplasia of the skull bones, which often leads to infant death

    Reduced amount of amniotic fluid (oligohydramnios) 1

Therefore, Losartan should not be used during pregnancy. There are other drugs which are also effective antihypertensive agents, and which have a much lower risk for your baby.

It is not known whether Losartan is excreted into breast milk, which is the reason why breastfeeding should be avoided while you're taking this drug.


The initial dose of Losartan is 50 mg once a day. The maintenance dose is 100 mg once a day. The maximum effect is expected after four weeks of treatment.

Losartan is often used in combination with diuretics (e.g. hydrochlorothiazide).

Losartan can be used in children aged 6-18 years, if necessary, but at a reduced dose.

It should not be used in children younger than 6 years.

Avoid eating too much of food that is rich in potassium (bananas, tomatoes, lettuce and etc.).


Drugs that may interact with Losartan are:

  • ACE inhibitors (e.g. enalapril, quinapril, ramipril, captopril, lisinopril and others). ACE inhibitors have a very similar effect as Losartan, and concomitant use would significantly increase the risk of hyperkalemia and renal impairment.
  • Potassium sparing diuretics
  • Bactrim (sulfamethoxazole / trimethoprim). This drug increases levels of potassium in the blood and should not be taken simultaneously with Losartan.
  • Non-steroidal anti-inflammatory drugs (e.g. ketoprofen, flurbiprofen, indomethacin, ibuprofen and etc.). These drugs reduce the antihypertensive effect of Losartan.

Side effects

During the Losartan therapy following side effects were reported:

  • Hepatocellular toxicity 2
  • Severe hyponatremia (headache, confusion, drowsiness, palpitations and nausea) 3
  • Angioedema 4,5
  • Psoriasis 6
  • Bronchospasm 7
  • Acute pancreatitis 8
  • Hypotension
  • Abdominal pain
  • Asthenia
  • Hyperkalemia
  • Allergy


  1. NCBI link 1
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  8. NCBI link 8

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