How does Losartan (angiotensin II receptor antagonist) affect potassium levels?

From the Guidelines

Losartan can increase potassium levels in the blood, potentially causing hyperkalemia in some patients. This angiotensin II receptor blocker works by blocking the effects of angiotensin II, which normally stimulates the release of aldosterone. When aldosterone release is reduced, the kidneys retain more potassium instead of excreting it, leading to elevated potassium levels 1. Patients taking Losartan should have their potassium levels monitored regularly, especially when starting treatment or adjusting dosage, as recommended by current guidelines 1.

Key Considerations

• The risk of hyperkalemia is higher in patients with kidney disease, diabetes, or those taking other medications that can raise potassium levels such as potassium supplements, potassium-sparing diuretics, or NSAIDs 1.
• Symptoms of high potassium include muscle weakness, irregular heartbeat, and numbness or tingling.
• Patients should be advised to avoid high-potassium foods and supplements while taking Losartan unless directed otherwise by their healthcare provider.
• If potassium levels become dangerously high, the medication dosage may need to be reduced or discontinued, and treatment with a K+ lowering agent should be initiated as early as possible 1.

Monitoring and Management

• Serum creatinine/estimated glomerular filtration rate and serum potassium levels should be monitored at least annually in patients treated with Losartan 1.
• Life-threatening hyperkalemia requires immediate treatment with a combination of calcium carbonate and hyperosmolar sodium, and potentially insulin, beta adrenoceptor agonists, and sodium bicarbonate 1.
• Loop diuretics and potassium binders can be used to manage hyperkalemia, and treatment should be initiated as early as possible to prevent rebound hyperkalemia 1.

From the FDA Drug Label

In spite of the effect of losartan on aldosterone secretion, very little effect on serum potassium was observed. Coadministration of losartan with other drugs that raise serum potassium levels may result in hyperkalemia. Monitor serum potassium in such patients. Dual blockade of the RAS with angiotensin receptor blockers, ACE inhibitors, or aliskiren is associated with increased risks of ... hyperkalemia ...

Losartan has a minimal effect on serum potassium levels due to its mechanism of action on aldosterone secretion. However, when coadministered with other drugs that raise serum potassium levels, it may result in hyperkalemia. Additionally, dual blockade of the renin-angiotensin system (RAS) is associated with an increased risk of hyperkalemia. Therefore, it is essential to monitor serum potassium levels in patients taking losartan with other medications that affect potassium levels 2, 2, 2.

• Key points:
  • Minimal effect on serum potassium levels
  • Risk of hyperkalemia when coadministered with other potassium-raising drugs
  • Risk of hyperkalemia with dual blockade of the RAS
  • Monitor serum potassium levels in patients taking losartan with other medications that affect potassium levels

From the Research

Effect of Losartan on Potassium Levels

• Losartan, an angiotensin II receptor antagonist, can affect potassium levels in the body, particularly when used with other medications such as potassium-sparing diuretics 3.
• The use of losartan with potassium-sparing diuretics, such as spironolactone or triamterene, may cause hyperkalemia 3.
• A study found that high-dose losartan increased the risk of hyperkalemia, while decreasing the risk of hypokalemia 4.
• Another study found that the concomitant use of losartan with spironolactone and furosemide may lead to an elevation of serum potassium levels, regardless of the dose of spironolactone 5.
• It is essential to monitor serum potassium levels when using losartan, especially when combined with other medications that can affect potassium levels 4, 5.

Mechanism of Action

• Losartan increases uric acid secretion and lowers plasma uric acid levels, which may be of benefit when combined with a thiazide diuretic, but which may otherwise lead to uric acid stone formation and possibly to nephropathy 6.
• Losartan may increase urinary excretion of uric acid, xanthine, and oxypurinol by acting on their common renal transport pathways 7.

Clinical Implications

• Hypokalemia (low potassium levels) is associated with a higher risk of cardiovascular death or heart failure hospitalization, all-cause death, and sudden cardiac death or resuscitated cardiac arrest 4.
• High-dose losartan decreased the risk of hypokalemia and increased the risk of hyperkalemia, but its benefits were maintained across the full spectrum of serum potassium at baseline 4.
• It is crucial to monitor serum potassium levels and adjust losartan dosage accordingly to minimize the risk of hyperkalemia or hypokalemia 4, 5.