From the Guidelines
Losartan can increase potassium levels in the blood, a condition known as hyperkalemia, due to its mechanism of action as an angiotensin II receptor blocker (ARB) that reduces aldosterone production, which normally promotes potassium excretion by the kidneys. This is a critical consideration in patients with kidney disease, diabetes, or those taking potassium supplements or potassium-sparing diuretics, as they are at higher risk of developing hyperkalemia 1.
Key Considerations
- Normal potassium levels range from 3.5 to 5.0 mEq/L, and levels above 5.5 mEq/L may require medical attention.
- Patients on losartan should be cautious about consuming high-potassium foods like bananas, oranges, tomatoes, potatoes, and salt substitutes.
- Signs of high potassium include muscle weakness, irregular heartbeat, and nausea, and if these symptoms occur, medical attention should be sought immediately.
- Doctors typically check potassium levels before starting losartan and periodically during treatment to ensure safety, with monitoring recommended at least monthly for the first 3 months and every 3 months thereafter 1.
Management of Hyperkalemia
- Life-threatening hyperkalemia requires immediate treatment with a combination of calcium carbonate and hyperosmolar sodium, as well as insulin and beta adrenoceptor agonists to transfer potassium into cells 1.
- Loop diuretics and potassium binders can be used to manage hyperkalemia, with the goal of reducing potassium levels and preventing cardiac arrhythmias and other complications 1.
From the FDA Drug Label
7.1 Agents Increasing Serum Potassium Coadministration of losartan with other drugs that raise serum potassium levels may result in hyperkalemia. Monitor serum potassium in such patients. 5.4 Hyperkalemia Monitor serum potassium periodically and treat appropriately. Dosage reduction or discontinuation of losartan may be required High blood levels of potassium
Losartan may increase potassium levels. It is recommended to monitor serum potassium periodically, especially when coadministered with other drugs that raise serum potassium levels, to prevent hyperkalemia 2, 2.
From the Research
Effect of Losartan on Potassium Levels
- Losartan has been reported to increase urinary potassium excretion 3, 4.
- In a study of hypertensive renal transplant recipients, losartan mildly affected serum potassium levels, with a slight increase from 4.3+/-0.5 to 4.5+/-0.5 mmol/l (P=0.25) 3.
- In contrast, enalapril significantly increased serum potassium levels from 4.3+/-0.5 to 4.8+/-0.4 mmol/l (P<0.05) in the same study 3.
- Another study found that losartan caused a transient rise in urinary potassium excretion in normotensive subjects 4.
- A study of patients with heart failure found that high-dose losartan (150 mg/d) increased the risk of hyperkalemia (HR 1.21,95% CI 1.05-1.39) and decreased the risk of hypokalemia (HR 0.77,95% CI 0.63-0.92) 5.
- In a study of patients with diabetic nephropathy, losartan increased serum potassium levels, but to a lesser extent than spironolactone 6.
Comparison with Other Medications
- Losartan has been compared to enalapril, an ACE inhibitor, in terms of its effect on potassium levels 3.
- Losartan has also been compared to spironolactone, a mineralocorticoid receptor blocker, in terms of its effect on potassium levels in patients with diabetic nephropathy 6.
- The study found that spironolactone raised serum potassium more than losartan in patients with diabetic nephropathy receiving lisinopril, despite similar renal sodium and potassium excretion 6.
Clinical Implications
- The effects of losartan on potassium levels should be considered when prescribing the medication, particularly in patients with renal impairment or those taking other medications that affect potassium levels 3, 5.
- Monitoring of serum potassium levels is recommended in patients taking losartan, especially in those with risk factors for hyperkalemia or hypokalemia 5.