Losartan Drug Profile

What is Losartan?

Losartan is a prescription medication that belongs to a class of drugs called angiotensin receptor blockers (ARBs). It is primarily used to treat high blood pressure (hypertension) and certain heart conditions by helping blood vessels relax and widen. Losartan was the first ARB approved by the FDA and has been widely prescribed since the 1990s.

Uses

• High blood pressure (hypertension): Losartan helps lower blood pressure by blocking the action of angiotensin II, reducing the risk of heart attack, stroke, and kidney problems.
• Diabetic kidney disease (diabetic nephropathy): In patients with type 2 diabetes, losartan can slow the progression of kidney damage and reduce protein in the urine.
• Heart failure: May be used when patients cannot tolerate ACE inhibitors, helping to reduce the workload on the heart.
• Stroke prevention: In patients with high blood pressure and left ventricular hypertrophy, losartan can reduce the risk of stroke.
• Chronic kidney disease: Helps protect kidney function in patients with high blood pressure and kidney disease.

How it works

Losartan works by blocking angiotensin II receptors in blood vessels, preventing a hormone called angiotensin II from binding to these receptors. Angiotensin II normally causes blood vessels to narrow and promotes sodium retention, which increases blood pressure. By blocking this action, losartan allows blood vessels to remain relaxed and dilated, reducing blood pressure and decreasing the strain on the heart and kidneys.

Side effects

Common side effects:

• Dizziness or lightheadedness
• Upper respiratory infections
• Fatigue or weakness
• Back pain
• Diarrhea
• Cough (less common than with ACE inhibitors)
• Low blood pressure (hypotension)
• Elevated potassium levels

Serious side effects requiring immediate medical attention:

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• Severe allergic reactions (swelling of face, lips, tongue, or throat)
• Kidney problems (decreased urination, swelling)
• Dangerously high potassium levels (irregular heartbeat, muscle weakness)
• Severe low blood pressure (fainting, severe dizziness)
• Liver problems (yellowing of skin or eyes, severe abdominal pain)

Warnings and precautions

• Pregnancy: Losartan can cause serious harm or death to an unborn baby when used during the second and third trimesters. Women should notify their doctor immediately if they become pregnant while taking this medication.
• Kidney function: Patients with severe kidney disease or those on dialysis should use losartan with caution, as it may worsen kidney function or cause dangerous electrolyte imbalances.
• Liver impairment: Patients with liver disease may need dose adjustments, as the liver processes losartan into its active form.
• Dehydration: Patients who are dehydrated, have low sodium levels, or are taking diuretics may experience severe drops in blood pressure when starting losartan.
• Heart conditions: Patients with severe heart failure or aortic stenosis should be monitored closely when starting treatment.

Interactions

• Potassium supplements and salt substitutes: Can cause dangerously high potassium levels when combined with losartan.
• NSAIDs (ibuprofen, naproxen): May reduce the blood pressure-lowering effects of losartan and increase the risk of kidney problems.
• Lithium: Losartan can increase lithium levels in the blood, potentially leading to lithium toxicity.
• Diuretics: Combined use may cause excessive drops in blood pressure, especially when starting treatment.
• Other blood pressure medications: May enhance the blood pressure-lowering effects, requiring dose adjustments.
• Rifampin: This antibiotic can reduce the effectiveness of losartan by increasing its metabolism.
• Fluconazole: This antifungal medication can increase losartan levels, potentially enhancing its effects.
• ACE inhibitors: Generally not recommended together due to increased risk of kidney problems and high potassium levels.

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Dosage

For adults with high blood pressure, the typical starting dose is 50 mg once daily, which may be increased to 100 mg once daily based on blood pressure response. For diabetic kidney disease, the usual dose is 50-100 mg once daily. Patients with liver problems or those taking diuretics may need to start with a lower dose of 25 mg daily. Losartan can be taken with or without food, and it’s important to take it at the same time each day. All dosage decisions should be made by a healthcare provider based on individual patient factors and response to treatment.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

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