Losartan

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 to protect the kidneys in people with diabetes. Losartan works by blocking certain receptors in blood vessels, allowing them to relax and reducing blood pressure.

Uses

Losartan is approved for several cardiovascular and kidney-related conditions:

• High blood pressure (hypertension): Losartan is commonly prescribed as a first-line treatment to lower blood pressure in adults and children over 6 years old
• Diabetic nephropathy: Helps protect kidney function in people with type 2 diabetes who have protein in their urine
• Heart failure: Used in combination with other medications to improve symptoms and reduce hospitalizations in patients with heart failure
• Stroke prevention: Prescribed for patients with high blood pressure and left ventricular hypertrophy to reduce the risk of stroke
• Chronic kidney disease: May be used to slow the progression of kidney disease in certain patients

How it works

Losartan blocks angiotensin II receptors in blood vessels and other tissues. Angiotensin II is a hormone that causes blood vessels to narrow and promotes sodium retention, both of which increase blood pressure. By blocking these receptors, losartan allows blood vessels to remain relaxed and dilated, which lowers blood pressure and reduces the workload on the heart and kidneys.

Side effects

Common side effects include:

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

Serious side effects that require immediate medical attention:

• Severe allergic reactions (swelling of face, lips, throat, difficulty breathing)
• Significant drop in blood pressure causing fainting
• Kidney problems (decreased urination, swelling in legs or feet)
• High potassium levels (muscle weakness, irregular heartbeat)
• Liver problems (yellowing of skin or eyes, severe abdominal pain)

Warnings and precautions

• Pregnancy: Losartan should not be used during pregnancy, especially in the second and third trimesters, as it can cause serious harm or death to the developing fetus
• Kidney disease: Patients with severe kidney impairment or those on dialysis may need dose adjustments or alternative treatments
• Liver disease: Those with liver problems may require lower starting doses as the medication is processed by the liver
• Dehydration: Patients should maintain adequate fluid intake, as dehydration can lead to dangerously low blood pressure
• Surgery: Inform healthcare providers about losartan use before any surgical procedures, as it may interact with anesthesia

Interactions

• Potassium supplements and salt substitutes: May cause dangerously high potassium levels when combined with losartan
• NSAIDs (ibuprofen, naproxen): Can reduce the blood pressure-lowering effects and may worsen kidney function
• Lithium: Losartan may increase lithium levels in the blood, potentially causing toxicity
• Diuretics: May cause excessive blood pressure reduction, especially when starting treatment
• ACE inhibitors: Combining with losartan increases risk of kidney problems and high potassium levels
• Rifampin: May reduce the effectiveness of losartan by increasing its breakdown in the liver
• Fluconazole: Can increase losartan levels in the blood, potentially enhancing its effects
• Heparin: May increase the risk of high potassium levels when used together

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Dosage

Typical adult dosages vary based on the condition being treated:

• Hypertension: Starting dose is usually 50 mg once daily, which may be increased to 100 mg once daily if needed
• Diabetic nephropathy: Typically 50 mg once daily, may be increased to 100 mg once daily based on blood pressure response
• Heart failure: Usually started at 12.5-25 mg once daily, gradually increased to a target dose of 50-150 mg once daily as tolerated

Dosage adjustments may be necessary for patients with liver problems or those taking certain other medications. Your healthcare provider will determine the most appropriate dose based on your individual medical condition 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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